Issues

Journal & Issues

Volume 84 (2022): Issue 1 (October 2022)

Volume 83 (2022): Issue 1 (August 2022)

Volume 82 (2022): Issue 1 (April 2022)

Volume 81 (2022): Issue 1 (January 2022)

Volume 80 (2021): Issue 1 (October 2021)

Volume 79 (2021): Issue 1 (July 2021)

Volume 78 (2021): Issue 1 (March 2021)

Volume 77 (2021): Issue 1 (January 2021)

Volume 76 (2021): Issue 1 (January 2021)

Volume 75 (2020): Issue 1 (October 2020)

Volume 74 (2020): Issue 1 (August 2020)

Volume 73 (2020): Issue 1 (July 2020)

Volume 72 (2020): Issue 1 (March 2020)

Volume 71 (2020): Issue 1 (January 2020)

Volume 70 (2019): Issue 1 (November 2019)

Volume 69 (2019): Issue 1 (October 2019)

Volume 68 (2019): Issue 1 (August 2019)

Volume 67 (2019): Issue 1 (June 2019)

Volume 66 (2019): Issue 1 (March 2019)

Volume 65 (2018): Issue 1 (December 2018)

Volume 64 (2018): Issue 1 (September 2018)

Volume 63 (2018): Issue 1 (August 2018)

Volume 62 (2018): Issue 1 (June 2018)

Volume 61 (2018): Issue 1 (March 2018)

Volume 60 (2017): Issue 1 (December 2017)

Volume 59 (2017): Issue 1 (October 2017)

Volume 58 (2017): Issue 1 (September 2017)

Volume 57 (2017): Issue 1 (June 2017)

Volume 56 (2017): Issue 1 (February 2017)

Volume 55 (2017): Issue 1 (January 2017)

Volume 54 (2016): Issue 1 (December 2016)

Volume 53 (2016): Issue 1 (December 2016)

Volume 52 (2016): Issue 1 (September 2016)

Volume 51 (2016): Issue 1 (June 2016)

Volume 50 (2016): Issue 1 (April 2016)

Volume 49 (2015): Issue 1 (December 2015)

Volume 48 (2015): Issue 1 (December 2015)

Volume 47 (2015): Issue 1 (September 2015)

Volume 46 (2015): Issue 1 (June 2015)

Volume 45 (2015): Issue 1 (March 2015)

Volume 44 (2014): Issue 1 (December 2014)

Volume 43 (2014): Issue 1 (November 2014)

Volume 42 (2014): Issue 1 (September 2014)

Volume 41 (2014): Issue 1 (June 2014)

Volume 40 (2014): Issue 1 (March 2014)

Volume 39 (2013): Issue 1 (December 2013)

Volume 38 (2013): Issue 2013 (September 2013)

Volume 37 (2013): Issue 1 (June 2013)

Volume 36 (2013): Issue 1 (March 2013)

Volume 35 (2012): Issue 1 (December 2012)

Volume 34 (2012): Issue 1 (October 2012)

Volume 33 (2012): Issue 2012 (June 2012)

Volume 32 (2012): Issue 2012 (May 2012)
Aquatic Sports and Activities

Volume 31 (2012): Issue 2012 (March 2012)

Volume 30 (2011): Issue 2011 (December 2011)

Volume 29A (2011): Issue Special-Issue (September 2011)
Presentation of the 1st International Symposium on Strength & Conditioning (ISSC 2011)

Volume 29 (2011): Issue 2011 (September 2011)

Volume 28 (2011): Issue 2011 (June 2011)

Volume 27 (2011): Issue 2011 (March 2011)

Volume 26 (2010): Issue 2010 (December 2010)

Volume 25 (2010): Issue 2010 (September 2010)

Volume 24 (2010): Issue 2010 (June 2010)

Volume 23 (2010): Issue 2010 (March 2010)

Volume 22 (2009): Issue 2009 (December 2009)

Volume 21 (2009): Issue 2009 (June 2009)

Volume 20 (2008): Issue 2008 (December 2008)

Volume 19 (2008): Issue 2008 (June 2008)

Journal Details
Format
Journal
eISSN
1899-7562
First Published
13 Jan 2009
Publication timeframe
5 times per year
Languages
English

Search

Volume 72 (2020): Issue 1 (March 2020)

Journal Details
Format
Journal
eISSN
1899-7562
First Published
13 Jan 2009
Publication timeframe
5 times per year
Languages
English

Search

26 Articles

Section I – Kinesiology

Open Access

Effects of Lower Extremity Muscle Fatigue on Knee Loading During a Forward Drop Jump to a Vertical Jump in Female Athletes

Published Online: 31 Mar 2020
Page range: 5 - 13

Abstract

Abstract

The aim of this study was to examine changes in the kinematic and kinetic parameters of female athletes performing a forward drop jump to a vertical jump under muscle fatigue condition. Twelve female college athletes performed a forward drop jump to a vertical jump with and without muscle fatigue conditions. A motion capture system and two AMTI force plates were used to synchronously collect kinematic and kinetic data. Inverse dynamics were implemented to calculate the participant’s joint loading, joint moment, and energy absorption. A paired sample t-test was used to compare statistical differences between pre-fatigue and post-fatigue conditions (α = .05). The forward trunk lean angle at initial foot contact, as well as the knee range of motion, total negative work and energy absorption contribution of the knee joint during the landing phase were significantly decreased under post-fatigue condition. The increased peak vertical ground reaction force and peak tibial anterior shear forces were also found under post-fatigue condition. These results indicated that muscle fatigue caused participants to change their original landing posture into stiff landing posture and decrease the energy absorption ability, which increased the tibial anterior shear forces. Therefore, female athletes should appropriately increase the knee flexion angle under muscle fatigue condition to reduce the risk of anterior cruciate ligament injuries.

Key words

  • energy absorption contribution
  • anterior cruciate ligament
  • joint moment
Open Access

Kinematic Analyses of Parkour Landings From as High as 2.7 Meters

Published Online: 31 Mar 2020
Page range: 15 - 28

Abstract

Abstract

Developing effective landing strategies has implications for both injury prevention and performance training. The purpose was to quantify the kinematics of Parkour practitioners’ landings from three heights utilizing four techniques. Seventeen male and three female Parkour practitioners landed from 0.9, 1.8, and 2.7 m utilizing the squat, forward, roll, and stiff landing techniques when three-dimensional kinematics were collected. The stiff landing demonstrated the shortest landing time, and the roll landing showed the longest landing time for 1.8 and 2.7 m. Roll landings demonstrated the greatest forward velocities at initial contact and at the end of the landing. Stiff landings showed the greatest changes in vertical velocity during the early landing, while roll landings showed the least changes for 0.9 and 1.8 m. Both roll and stiff landings generally resulted in decreased changes in horizontal velocity during the early landing compared to squat and forward landings. The four landing techniques also demonstrated different lower extremity joint angles. Stiff landings may increase injury risk because of the quick decrease of vertical velocities. Roll landings allow individuals to decrease vertical and horizontal velocities over a longer time, which is likely to decrease the peak loading imposed on the lower extremities.

Key words

  • jump-landing
  • impact
  • injury
  • performance
  • lower extremities
Open Access

Movement Variability During the Flight Phase in a Single Back Sideflip (Wildcat) in Snowboarding

Published Online: 31 Mar 2020
Page range: 29 - 38

Abstract

Abstract

Understanding the structure and variability of motion is essential for sports technique development and an effective training design. Biomechanical analysis is particularly important in new disciplines with spatially complex motions, such as snowboarding. This study aimed to evaluate the level of variability of the kinematic variables in a single backside snowboard flip known as a “wildcat”. Forty-six correct flips performed by 7 experienced athletes (age: 24.9 ± 4.34 year; body mass: 71.6 ± 12.87 kg; body height: 177.4 ± 6.99 cm) were recorded using an optoelectronic VICON system in the controlled setting of an indoor freestyle park. Athletes were equipped with special boards with wheels and the geometry of the ramps corresponded to the actual on-snow conditions. The analysis revealed two distinct single flip strategies, which differed in the way the tuck position was sustained. For all the measured variables, the coefficient of variation was computed, which allowed to identify the athlete with the highest (average 45.3%) and lowest (average 20.5%) variability of kinematic variables. Moreover, it was shown that the lowest values of the coefficient of variation occurred at the end of the grouping phase (average 14%) and that among all the different variables, those related to the duration of motion were most unstable (average 63%, SD = 48.5%).

Key words

  • snowboarding
  • sports technique
  • movement variability
  • motion capture
Open Access

How do Amateur Endurance Runners Alter Spatiotemporal Parameters and Step Variability as Running Velocity Increases? A Sex Comparison

Published Online: 31 Mar 2020
Page range: 39 - 49

Abstract

Abstract

This study aimed to analyse the effects of running velocity on spatiotemporal parameters and step variability in amateur endurance runners, according to sex. A group of 51 males and 46 females performed an incremental running test on a treadmill (10-16 km/h). Spatiotemporal parameters (contact and flight time, step length, step frequency and step angle [CT, FT, SL, SF, SA]) and step variability, in terms of within-participant standard deviation (SD), were recorded through the OptoGait System. The ANOVA showed significant differences in the magnitude of the spatiotemporal parameters as running velocity increased (p < 0.001). It also revealed significant differences in step variability (p < 0.005) over the entire running protocol. Between-sex differences in CT, SL, SL-normalized and SF (p < 0.05, ES = 0.4-0.8) were found. Differences were also found in step variability at high velocities (15-16 km/h), with males showing a greater SD than females. In conclusion, increasing running velocity makes CT shorter, FT and SL longer, and SF and SA greater in amateur endurance runners, changing step variability, regardless of sex. Additionally, some between-sex differences were found in spatiotemporal parameters and step variability.

Key words

  • gender
  • biomechanics
  • kinematics
  • running
Open Access

Muscle Recruitment Pattern of The Hamstring Muscles in Hip Extension and Knee Flexion Exercises

Published Online: 31 Mar 2020
Page range: 51 - 59

Abstract

Abstract

We aimed to compare dynamic exercise performance between hip extension exercises with different knee angles and between knee flexion exercises with different hip angles, and to investigate the recruitment pattern of the hamstrings in each exercise. Seven men performed 4 isokinetic exercises (3 maximal concentric contractions at 30°/s (peak torque) and 30 maximal concentric contractions at 180°/s (total work)): hip extension with the knee fully extended (HEke) and with the knee flexed at 90° (HEkf) and knee flexion with the hip fully extended (KFhe) and with the hip flexed at 90° (KFhf). The recruitment pattern of the hamstrings was evaluated in each exercise using magnetic resonance imaging (T2 calculation). The HEke condition showed significantly greater peak torque than the HEkf condition (p < 0.05). The KFhf condition had significantly greater peak torque and total work values than the KFhe condition (p < 0.05). Although the biceps femoris long head, semitendinosus, and semimembranosus had significantly increased post-exercise T2 values in the HEke (p < 0.05), KFhe, and KFhf conditions (p < 0.01), the T2 increase values were significantly greater under the KFhf than the HEke condition (p < 0.05). The semitendinosus showed a significantly greater T2 increase value than other muscles under both KFhe and KFhf conditions (p < 0.05). Performance of hip extension and knee flexion exercises increases when the hamstring muscles are in a lengthened condition. The hamstring muscles (particularly the semitendinosus) are more involved in knee flexion than in hip extension.

Key words

  • magnetic resonance imaging
  • T2 relaxation time
  • isokinetic exercise
  • biceps femoris
  • semitendinosus
  • semimembranosus
Open Access

The Transition from Underwater to Surface Swimming During the Push-off Start in Competitive Swimmers

Published Online: 31 Mar 2020
Page range: 61 - 67

Abstract

Abstract

The objective of the present study was to analyze (based on gender and the style of swimming) the kinematic parameters of the transition phase between underwater swimming and surface swimming after the push-off start in competitive national swimmers. Seventy-four swimmers participating in the Spanish Swimming Championships were filmed and analyzed by DLT-2D photogrammetry during the start with the push-off in crawl, backstroke and butterfly styles. Between genders there were small differences in the distance and speed of transition. The male swimmers travelled greater distances (0.84 ± 0.04 vs. 0.66 ± 0.04 m, η2 = 0.05, F = 10.34, p < 0.001) and they were faster (1.59 ± 0.03 vs. 1.38 ± 0.03 m/s, η2 = 0.08, F = 19.54, p < 0.001) in the transition phase than female swimmers. Among styles there were greater differences in time (η2 = 0.47, F = 94.50, p < 0.001) and transition distance (η2 = 0.38, F = 67.08, p < 0.001), than in speed (η2 = 0.05, F = 5.63, p < 0.001). During the backstroke push-off, swimmers spent more time (0.88 ± 0.04 s) and distance (1.17 ± 0.05 m), this being the slowest style (1.37 ± 0.04 m/s). In butterfly, athletes used less time (0.26 ± 0.03 s) and distance (0.39 ± 0.05 m) whereas crawl was the fastest of all (1.57 ± 0.04 m/s). These results allow the phase of transition from underwater to surface swimming to be characterized and to provide useful data for competitive swimmers and coaches to improve performance.

Key words

  • biomechanics
  • kinematics
  • performance
  • direct linear transformation
  • 2D

Section II – Exercise Physiology & Sports Medicine

Open Access

Effects of Oral Branched‐Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise

Published Online: 31 Mar 2020
Page range: 69 - 78

Abstract

Abstract

The aim of this study was to investigate the effects of oral branched-chain amino acids (BCAAs) intake on muscular (creatine kinase and myoglobin) and central (serotonin) fatigue during an incremental exercise protocol and to determine the time to exhaustion. Sixteen male long-distance runners (25.7 ± 2.0 yrs) performed two trials, 14 days apart. Using a double-blind, placebo-controlled, randomised crossover design, participants ingested either 20 g of BCAAs (BCAA trial) or a placebo 1 hour prior to performing an incremental exercise session on a treadmill. The starting speed was 8 km/h and this was increased by 1 km/h every 5 minutes until volitional exhaustion. Blood analysis indicated that plasma levels of serotonin were lower in the BCAA trial (259.3 ± 13.5 ng/ml) than the placebo trial (289.1 ± 14.5 ng/ml) (p < 0.05). There was a similar pattern of results for free fatty acid (p < 0.05). The creatine kinase level was higher in the BCAA trial (346.1 ± 33.7 U/L) than the placebo trial (307.3 ± 30.2 U/L). No significant difference between trials was observed regarding the level of myoglobin (p = 0.139). Time to exhaustion was longer in the BCAA trial (50.4 ± 2.3 min) than the placebo trial (46.6 ± 3.2 min). In conclusion, oral intake of 20 g of BCAAs 1 hour prior to an incremental treadmill exercise session increased time to exhaustion, probably due to the reduction in serotonin concentration. As myoglobin levels were within the normal range in both trials, we conclude that the participants did not reach muscular fatigue.

Key words

  • Serotonin
  • free fatty acid
  • endurance exercise
  • myoglobin
Open Access

Analysis of Polymorphic Variants of the Dopamine Transporter (DAT1) Gene Polymorphism and Personality Traits Among Athletes

Published Online: 31 Mar 2020
Page range: 79 - 89

Abstract

Abstract

Personality traits, especially in sport are modulatory factors of athletes’ behavior – his/ her conscientiousness, the will to achieve an aim, perseverance and motivation of activity. Not only are biological predispositions related to anatomical or biochemical traits of success, but they are also largely determined by personality traits that result from genetic factors. In our research we joined tests of athlete’s personality in correlation with genotypes of the dopamine transporter (DAT1) gene polymorphism. The selection of this polymorphism was based on previous reports connecting the influence of dopamine with motivation and numerous arguments supporting its correlation with human behavior. We observed significant differences among polymorphisms DAT 9/9, 9/10, 10/10 in terms of proportion of particular genotypes between athletes and the control group. We also found significant differences in the NEO FFI sten scale for conscientiousness. We noticed that anxiety was related with genotypic variants of DAT1, specifically the 9/10 VNTR variant, which conditioned lower levels of anxiety in the group of tested athletes. By contrast, the lower sten value of agreeability was statistically significant for the group of athletes that were carriers of the 10/10 VNTR genotype. Heterozygous 9/10 VNTR among athletes showed lower levels of anxiety in comparison with the control group, whereas agreeability determined using the NEO FFI scale represented a lower value among athletes that had the 10/10 polymorphism. We may thus conclude that the presence of polymorphic variants of the dopamine transporter gene corresponds to athletes’ personality traits.

Key words

  • dopamine
  • personality
  • athletes
Open Access

Physical and Physiological Response to Different Modes of Repeated Sprint Exercises in Basketball Players

Published Online: 31 Mar 2020
Page range: 91 - 99

Abstract

Abstract

The aim of this study was to investigate changes in physical and physiological responses to different modes of repeated sprint exercise by measuring speed, total time (sum of sprints), fatigue index, heart rate, local oxygen saturation, total haemoglobin content, and blood lactate. The volume of the physical load (distance, work and rest ratio) was the same in both exercises, but load specifics were different. The first mode consisted of 10 x 30 m sprints (with one change of direction) interspersed with 30 s of passive recovery, while the second mode of 20 x 15 m shuttle sprints interspersed with 15 s of passive recovery. Both exercise modalities were repeated three times with a five-minute rest interval between bouts with 7 days of recovery between each testing condition. Twelve highly trained male basketball players volunteered to participate in this study. Our study showed that different modes of repeated sprint exercises elicited a different physical response and metabolic demand. Longer sprints with directional changes placed a higher demand on the anaerobic glycolytic system compared to straight and more frequent sprint exercises. However, players’ fatigue was more noticeable in shorter and more frequent sprints. Heart rate responses and local use of O2 showed a similar activity of aerobic reactions through the different exercises. During the sprints, players’ SmO2 fell to 40% and recovered to the level of about 80% during passive rest intervals without showing differences in both modalities. This suggests that both types of sprint exercises can similarly stimulate aerobic metabolism.

Key words

  • local oxygen saturation
  • blood lactate
  • heart rate
  • speed
  • fatigue index
Open Access

The Impact of Aspirin Intake on Lactate Dehydrogenase, Arterial Stiffness, and Oxidative Stress During High‐Intensity Exercise: A Pilot Study

Published Online: 31 Mar 2020
Page range: 101 - 113

Abstract

Abstract

Aspirin is a common nonsteroidal anti-inflammatory drug used to reduce fever, pain, and inflammation. However, aspirin’s anti-inflammatory properties may also prevent increased levels of blood lactate dehydrogenase, vascular arterial stiffness and oxidative stress induced by high-intensity exercise. The purpose of this study was to investigate the effects of 4 weeks of aspirin supplementation on lactate dehydrogenase activity, lactate, arterial stiffness, and antioxidant capacity during high-intensity exercise in Taekwondo athletes. Participants were randomly divided into two groups: aspirin supplementation (n = 10) and placebo-control (n = 10). Blood levels of lactate dehydrogenase (LDH) enzyme activity and lactate were assessed to examine muscle damage and carotid-to-radial pulse wave velocity and the augmentation index were measured to examine arterial stiffness. Blood levels of superoxide dismutase, malondialdehyde, and glutathione peroxidase were assessed to determine antioxidant capacity and levels of oxidative stress. There were significant group × time interactions for enzyme activity of LDH (Δ-60 ± 24.36 U/L) and carotid-to-radial pulse wave velocity (Δ-1.33 ± 0.54 m/s), which significantly decreased (p < 0.05) following aspirin supplementation compared to placebo-control. Superoxide dismutase (Δ359 ± 110 U/gHb) and glutathione peroxidase (Δ28.2 ± 10.1 U/gHb) significantly decreased while malondialdehyde (0Δ3.0 ± 0.1 mmol/mL) significantly increased (p < 0.05) in the placebo-control group compared to the supplementation group. However, there were no changes in lactate concentration levels or augmentation index. These results reveal that low-dose aspirin supplementation would be a useful supplementation therapy to prevent high-intensity exercise training-induced increases in oxidative damage, inflammation, skeletal muscle fatigue, and arterial stiffness in elite Taekwondo athletes.

Key words

  • antioxidant capacity
  • high-intensity training
  • NSAID
  • pulse wave velocity
Open Access

Effects of an Exogenous Ketone Supplement on Five‐Kilometer Running Performance

Published Online: 31 Mar 2020
Page range: 115 - 127

Abstract

Abstract

Numerous oral ketone supplements are marketed with the claim that they will rapidly induce ketosis and improve exercise performance. The purpose of this study was to assess exercise performance time and related physiological, metabolic and perceptual responses of recreational endurance runners after ingestion of a commercially available oral ketone supplement. Recreational endurance runners (n = 10; age: 20.8 ± 1.0 years; body mass: 68.9 ± 5.6 kg; height: 175.6 ± 4.9 cm) participated in a double-blind, crossover, repeated-measures study where they were randomized to 300 mg.kg-1 body weight of an oral β-hydroxybutyrate-salt + Medium Chain Triglyceride (βHB-salt+MCT) ketone supplement or a flavor matched placebo (PLA) 60 min prior to performing a 5-km running time trial (5KTT) on a treadmill. Time, HR, RPE, affect, RER, VO2, VCO2, and VE were measured during the 5-km run. The Session RPE and affect (Feeling Scale) were obtained post-5KTT. Plasma glucose, lactate and ketones were measured at baseline, 60-min post-supplement, and immediately post-5KTT. Plasma R-βHB (endogenous isomer) was elevated from baseline and throughout the entire protocol under the βHB-salt+MCT condition (p < 0.05). No significant difference (58.3 ± 100.40 s; 95% CI: -130.12 – 13.52; p = 0.100) was observed between the βHB-salt+MCT supplement (1430.0 ± 187.7 s) and the PLA (1488.3 ± 243.8 s) in time to complete the 5KTT. No other differences (p > 0.05) were noted in any of the other physiological, metabolic or perceptual measures.

Key words

  • ketosis
  • beta-hydroxybutyrate
  • dietary supplements
  • ergogenic aid
Open Access

What are the Limiting Factors During an Ultra‐Marathon? A Systematic Review of the Scientific Literature

Published Online: 31 Mar 2020
Page range: 129 - 139

Abstract

Abstract

This review aimed to analyse factors that limited performance in ultra-marathons and mountain ultra-marathons. A literature search in one database (PubMed) was conducted in February 2019. Quality of information of the articles was evaluated using the Oxford´s level of evidence and the Physiotherapy Evidence Database (PEDro) scale. The search strategy yielded 111 total citations from which 23 met the inclusion criteria. Twenty one of the 23 included studies had a level of evidence 2b (individual cohort study), while the 2 remaining studies had a level of evidence of 5 (expert opinion). Also, the mean score in the PEDro scale was 3.65 ± 1.61, with values ranging from 0 to 7. Participants were characterised as experienced or well-trained athletes in all of the studies. The total number of participants was 1002 (893 men, 86 women and 23 unknown). The findings of this review suggest that fatigue in ultra-endurance events is a multifactorial phenomenon that includes physiological, neuromuscular, biomechanical and cognitive factors. Improved exercise performance during ultra-endurance events seems to be related to higher VO2max values and maximal aerobic speed (especially during submaximal efforts sustained over a long time), lower oxygen cost of transport and greater running experience.

Key words

  • trail running
  • VO
  • performance
  • fatigue
  • endurance
Open Access

Heart Rate Variability is Correlated with Perceived Physical Fitness in Elite Soccer Players

Published Online: 31 Mar 2020
Page range: 141 - 150

Abstract

Abstract

Heart Rate Variability (HRV) has been typically used to monitor athletes’ physical fitness readiness. The supine position maximizes parasympathetic tone, which is important for monitoring in continuous aerobic sports, however, this is not the case of team sports that rely on anaerobic intermittent bouts, thus increasing sympathetic activation and vagal withdrawal. We hypothesized that HRV during sympathetic activation and vagal withdrawal would be a useful marker to evaluate perceived physical fitness in team sports. HRV was measured in both supine and standing positions during the mornings of 4 match days in 14 professional players. The supine Root Mean Square of the Successive Differences (RMSSD), as well as spectral analysis indices were recorded. Perceived physical fitness was assessed after each match by means of a visual analogue scale (VAS). Supine RMSSD was moderately correlated with perceived physical fitness (rho = 0.416), however, larger correlations were observed for supine and standing spectral indices (rho > 0.5). Correlation between RMSSD and Total Power was very large, thus questioning the usual interpretation of RMSSD (rho > 0.7). Standing Spectral HRV analyses may be a useful method for evaluating perceived physical fitness in the context of team sports. RMSSD may reflect the overall variability of HR and not only the parasympathetic influence, as observed in the current study.

Key words

  • autonomic nervous system
  • soccer
  • training, intermittent sports
  • orthostatic test

Section III – Sports Training

Open Access

The Effects of the Movement Tempo on the One-Repetition Maximum Bench Press Results

Published Online: 31 Mar 2020
Page range: 151 - 159

Abstract

Abstract

Different tempos of movement can be used during resistance training, but programming them is often a trial-and-error practice, as changing the speed at which the exercise is performed does not always correspond with the tempo at which the 1-repetition-maximum occurred. Therefore, the aim of this study was to determine the effect of different movement tempos during the bench press (BP) exercise on the one-repetition maximum (1RM) load. Ninety men (age = 25.8 ± 5.3 years, body mass = 80.2 ± 14.9 kg), with a minimum one year of resistance training experience took part in the study. Using a randomized crossover design, each participant completed the BP 1RM test with five different movement tempos: V/0/V/0, 2/0/V/0, 5/0/V/0, 8/0/V/0 and 10/0/V/0. Repeated measures ANOVA compared the differences between the 1RM at each tempo. The 1RM load was significantly greater during V/0/V/0 and 2/0/V/0 compared to 5/0/V/0, 8/0/V/0, and 10/0/V/0 (p < 0.01). Furthermore, the 1RM load was significantly greater during 5/0/V/0 compared to 8/0/V/0 and 10/0/V/0 (p < 0.01), but there were no differences between either V/0/V/0 and 2/0/V/0 (p = 0.92) or between 8/0/V/0 and 10/0/V/0 (p = 0.08). Therefore, different movement tempos used during training should be accompanied by their own tempo-specific 1RM testing, as slower eccentric phases significantly decrease maximal concentric performance. Furthermore, 1RM test procedures should include information about the movement tempo used during the test protocol. In addition, the standardization of the tempo should be taken into account in investigations that use the 1 RM test to assess the effects of any treatment on maximal muscle strength.

Key words

  • eccentric movements
  • duration of repetition
  • maximal strength
  • external load
  • resistance training
Open Access

Acute Effects of a Static vs. a Dynamic Stretching Warm-up on Repeated-Sprint Performance in Female Handball Players

Published Online: 31 Mar 2020
Page range: 161 - 172

Abstract

Abstract

This randomized cross-over study examined the effects of typical static and dynamic stretching warm-up protocols on repeated-sprint performance. Thirteen young female handball players performed a 5 min aerobic warm-up followed by one of three stretching protocols for the lower limbs: (1) static stretching, (2) dynamic-ballistic stretching, and (3) no stretching before performing five all-out sprints on a cycle ergometer. Each protocol was performed on a different occasion, separated by 2-3 days. Range of movement (ROM) was also measured before and after the warm-up protocols with a sit-and-reach test. Fixed and random effects of each stretching protocol on repeated sprint performance were estimated with mixed linear modeling and data were evaluated via standardization and magnitude-based inferences. In comparison to no stretching, there were small increases in ROM after dynamic stretching (12.7%, ±0.7%; mean, ±90% confidence limits) and static stretching (19.2%, ±0.9%). There were small increases in the average power across all sprints with dynamic stretching relative to static stretching (3.3%, ±2.4%) and no stretching (3.0%, ±2.4%) and trivial to small increases in the average power in the 1st and 5th trials with dynamic stretching compared to static stretching (3.9%, ±2.6%; 2.6%, ±2.6%, respectively) and no stretching (2.0%, ±2.7%; 4.1%, ±2.8%, respectively). There were also trivial and small decreases in power across all sprints with static relative to dynamic stretching (-1.3%, ±2.8%) and no stretching (-3.5%, ±2.9%). Dynamic stretching improved repeated-sprint performance to a greater extent than static stretching and no stretching.

Key words

  • performance
  • team sport athletes
  • high-intensity
  • modeling
Open Access

The Relative Age Effect in Professional Futsal Players

Published Online: 31 Mar 2020
Page range: 173 - 183

Abstract

Abstract

The objective of this study was to verify the occurrence and effect size of relative age effect in professional futsal players, by observing how its presence and impact change according to the season, team level and player position. The sample was composed of 1873 professional futsal players who played in the First Division of the Spanish National Futsal League between seasons 2006-2007 and 2014-2015. The players’ birthdates were divided into quarters (Q1, Q2, Q3 and Q4). A relative age effect reversal was observed in the professional futsal players for the nine analyzed seasons. A relative age reversal effect was observed in high and medium level teams. Finally, a relative age effect reversal was also found for the goalkeeper and pivot positions. The results could suggest that players that initially experienced maturity disadvantages in major sports, can have a second chance to emerge in professional minor sports (i.e. futsal vs. soccer). However, the underlying mechanisms why a reversal occurs are still unclear, and more studies focusing on the mediators of the effect are needed.

Key words

  • talent development
  • performance analysis
  • team level
  • playing position
  • team sport
Open Access

Quantification of Movement Characteristics in Women’s English Premier Elite Domestic Rugby Union

Published Online: 31 Mar 2020
Page range: 185 - 194

Abstract

Abstract

This study aims were to determine the positional physical requirements of English domestic women’s rugby union match-play. Global positioning system data (Catapult Minimax S4) were collected at 10 Hz of 129 competitive player games from the Tyrrells Premier15 league. Players were classified according to broad (Forwards, Backs) and specific positions (front-, second-, back-row, scrum-half, inside-, and outside-backs). Total distances, maximum speed, and player loads were calculated. Mean total distance was 4982 m and was similar between the Forwards and Backs, with second-row players covering the most (5297 m) and outside-backs the least (4701 m). Inside- and outside-backs covered a significantly greater distance at high speed running (134 m; 178 m) and sprinting (74 m; 92 m) speeds, respectively, whereas the second- and back-row covered greater distances jogging (1966 m; 1976 m) and the front-row spent the greatest overall distance walking (2613 m). Outside-backs reached greater maximum speed than all other positions (24.9 km.h-1). The mean player load was highest in the back-row (562 AU) and second-row (555 AU) and these were higher than the outside-backs (476 AU). These findings indicate that the demands placed on female rugby players are position specific and differ from male players. Additionally, the data are the first obtained from the 10 Hz GPS and from within English domestic women’s rugby, thus adding to the overall limited data available on women’s rugby union.

Key words

  • movement patterns
  • workload
  • Global Positioning System
  • positional demands
Open Access

Relative Age Effect in the Girls’ Volleyball U18 World Championship

Published Online: 31 Mar 2020
Page range: 195 - 202

Abstract

Abstract

The relative age effect (RAE), within the sporting scope, refers to the possible advantages of participation and performance of athletes born in the first months of the year of selection in relation to others within the same age category. The aim of the present study was to investigate the RAE in girls’ volleyball players participating in the U-18 World Championship, analysing the differences between the medal teams and other teams in the tournament, and considering this phenomenon in relation to the continents. Data collection was obtained from the website of the International Volleyball Federation with a sample made of 1654 youth players in the last six world championships (2007, 2009, 2011, 2013, 2015 and 2017). A greater representation of athletes born in the first months of the year of all the world championships was observed. In the comparison among the continents, it was observed that in Africa, there was a more equal distribution of quartiles compared to America, Asia and Europe. It should be noted that there was a higher percentage of medalist athletes born at the beginning of the year in comparison to the countries that placed in the last three positions of the championship. Therefore, in U-18 female volleyball, there is an advantage to have the closest birth age at the beginning of the competitive biennium.

Key words

  • youth
  • volleyball
  • birth date
  • player selection
  • age effect
Open Access

Water Polo Shooting Performance: Differences Between World Championship Winning, Drawing and Losing Teams

Published Online: 31 Mar 2020
Page range: 203 - 214

Abstract

Abstract

Shooting performance of globally ranked winning, drawing and losing water polo teams was compared, and technical and tactical success indicators were identified. In total, 886 shots from a world championship final round were videotaped and teams were clustered for a performance evaluation (considering differences between game outcomes). Shooting speeds were assessed by a radar, with higher values observed at further distances from the goal than in the central area close to the goal (p ≤ 0.00, ES: 2.54). Shots tended to be more frequent from the central corridor, with ≤50% and >75% relative shot efficacy attained from field areas 3 and 6; winning teams obtained better results. Furthermore, winners had greater success than losers when shooting from field area 2 (p ≤ 0.04, ES: 1.13) and towards the goal zone 2 (p < 0.03, ES: 1.10). They also attained better efficacy regarding shots towards goal zone 1, had better efficacy on the part of centre-forwards (p ≤ 0.05, ES: 0.85-1.27), and were more effective regarding shots without a frontal defensive block. In addition, contingency analysis highlighted shots performed from field area 6, without a defensive block, toward the bottom left goal corner, and through man-up play as success indicators (all for p ≤ 0.005). We concluded that world-level winning teams homogeneously distributed their shot opportunities at the second offensive line with balanced efficacy, creating variability and uncertainty in their opponents’ defensive action. Elite level players must be capable of interpreting game situations with intelligence and proper decision making. This information may be useful for improving teams performance.

Key words

  • match analysis
  • performance indicators
  • expert teams
  • success
Open Access

Match Performance Indicators that Discriminated Between Winning, Drawing and Losing Teams in the 2017 AFCON Soccer Championship

Published Online: 31 Mar 2020
Page range: 215 - 221

Abstract

Abstract

The purpose of this study was to examine match performance indicators that discriminated between winning, drawing and losing teams in the 2017 Total Africa Cup of Nations (AFCON) soccer championship. Data were collected from 32 matches during the AFCON soccer tournament using the InStat® system. The studied variables included the number of goals scored, the time period in which a goal was scored and the impact of the first goal on the match outcome, as well as total shots, shots on goal, total passes, accurate passes, corners, ball possession, fouls, offsides as well as yellow and red cards. The results showed that goals scored (1.80 ± 0.83), total shots (11.05 ± 4.83), shots on target (4.70 ± 2.62), fouls (18.60 ± 5.19), offsides (2.35 ± 1.76), yellow cards (1.55 ± 1.10), and red cards (0.05 ± 0.22) were discriminative performance indicators of winning teams. In contrast, losing teams yielded higher mean values in total passes (260.30 ± 49.10), accurate passes (69.28 ± 5.74), corners (5.10 ± 2.95), and ball possession (51.20 ± 5.52). In conclusion, these results have practical implications for coaches in planning and implementing team tactics for successful performance.

Key words

  • performance
  • game-related statistics
  • goals
  • team sports
Open Access

Activity of Trunk and Lower Extremity Musculature: Comparison Between Parallel Back Squats and Belt Squats

Published Online: 31 Mar 2020
Page range: 223 - 228

Abstract

Abstract

The back squat is widely used in strength training programs. Alternatively, the belt squat has been gaining popularity since it loads the weight on the hips, as opposed to the shoulders and spine. The purpose of this study was to determine whether using a belt squat would result in less lumbar extensor activation while providing similar excitation of other prime mover and stabilizer musculature. Ten participants (9 males, 1 female; age 29.3 ± 4.9 years; body mass 96.2 ± 17.8 kg) who regularly trained both belt squats and back squats performed three sets of 5 repetitions with 100% bodyweight for each exercise. Peak and integrated muscle activity was calculated and normalized to a maximum voluntary isometric contraction. A one-way ANOVA (p < 0.05) was used to compare conditions. Belt squatting decreased lumbar erector impulse (45.4%) and peak (52.0%) activation as compared to the back squat. Belt squatting did not alter activation of the lower extremities except for a decrease in the gluteus maximus (35.2% impulse and 32.1% peak), gluteus medius (54.1% impulse and 55.2% peak). Furthermore, belt squatting reduced activation of the rectus abdominus (44.3% impulse; 31.1% peak), and external obliques (45.8% impulse; 53.7% peak) as compared to back squatting. Our results suggest belt squatting provides similar muscular demands for the quadriceps, hamstrings, and plantar flexors, but is less demanding of trunk stabilizers, and gluteual muscles. Belt squats may be a suitable alternative to back squats in order to avoid stressing low back or trunk musculature.

Key words

  • low back
  • resistance training
  • EMG
Open Access

Assessing Change of Direction Ability in a Spanish Elite Soccer Academy

Published Online: 31 Mar 2020
Page range: 229 - 239

Abstract

Abstract

The aims of the study were: a) to analyze the reproducibility of the Modified Agility Test (MAT) according to two types of displacement (i.e. constrained [MATtop] vs. free [MATfree]), b) to examine the explanatory capacity of anthropometric characteristics and neuromuscular performance on the ability to change the direction (CODA), c) to look into the practical consequences of the types of displacement from the perspective of an elite soccer academy. 118 male soccer players (age: 16 (13-25) years old) from the same elite Spanish soccer academy (U13 to senior) were tested twice on two versions of the MAT (MATtop and MATfree), with 48 hours between testing sessions. Moreover, they were tested on linear-sprint performance, over 5 m (S5m) and 15 m (S15m), and the vertical jump (VJ) (countermovement jump with [ACMJ] and without an arm swing [CMJ]). The main findings were: a) the type of displacement did not affect the reliability of the CODA test; b) weight, S15m, ACMJ and CMJ variables explained close to 60% of CODA performance; c) MATtop (i.e. constrained displacement) and MATfree (i.e. free-displacement) CODA tests could show different profiles of development along the age groups; and d) the impact of the task’s constraints was relatively higher in U16 and U17 groups. CODA seems to have a variable meaning depending on the characteristics of the test and the age of the participants.

Key words

  • agility
  • test
  • youth
  • soccer
  • athletics
Open Access

Making Decisions and Motor Actions with Technical Biomechanical Classifications in Male Judo Weight Categories

Published Online: 31 Mar 2020
Page range: 241 - 252

Abstract

Abstract

The aim of the study was to compare motor action variables of judo combat phases and technical biomechanical assessment of the seven weight categories. The sample was composed of 638 bouts (176 of extra lightweight <66 kg, 289 of half lightweight 66 > 73 kg, 180 of lightweight 73 > 81 kg, 244 of half middleweight 81 > 90 kg, 174 of middleweight 81 > 90 kg, 151 of half heavyweight 90 > 100 kg and 142 of heavyweight >100 kg) during motor actions of approach, gripping, attack, defense and groundwork combat phases, verifying the interactions between them by Markov chains and comparisons by Kruskall-Wallis and Dunn post hoc tests (p ≤ .05). The results demonstrated that lighter weight categories showed higher approach phases than the heavyweight category, and the lightweight group demonstrated higher defensive action frequencies than the half lightweight category and heavyweight athletes. Heavyweight and middleweight categories demonstrated higher groundwork combat frequencies than lighter weights, and the heavyweight category showed higher pause frequencies than the lightweight category. Regarding the decision-making model, the main transitions presented by the Markov chains showed higher prevalence of the following combinations: gripping occurring before the lever and length attacks, lever attack followed by the length attack, and length attack occurring earlier than the groundwork phase.

Key words

  • martial arts
  • biomechanics
  • performance analysis
  • motor control
  • time motion analysis
  • circuit-based exercise
Open Access

Physical and Physiological Demands During Handball Matches in Male Adolescent Players

Published Online: 31 Mar 2020
Page range: 253 - 263

Abstract

Abstract

This study aimed to describe the physical and physiological demands of adolescent handball players and compare movement analysis and exercise intensities between the first and second halves and between the different periods of the match. Fourteen adolescent handball players (age 15.7 ± 0.8 years, body mass: 65.6 ± 3.4 kg, body height: 169.5 ± 3.9 cm), played two friendly matches, in which no substitutions were made. The analysis was carried out with a Global Positioning System technology. The following physical variables were analyzed: Total distance covered (TD); distance covered at faster velocities than 18 km·h-1 (TDC>18km·h-1); number of accelerations (Accel) and decelerations (Decel); number of accelerations and decelerations higher than 2.78 m·s-2 (Accel>2.78 m·s-2 and Decel>2.78 m·s-2); number of sprints (Sprints); accelerations interspersed with a maximum of 30 s between them (RAS≤30s) and as a physiological variable the heart rate (HR) was examined. Significant differences (p < 0.01 –p < 0.001) between the first and the second half in all variables mentioned were observed, except in Accel>2.78 m·s-2 and Decel>2.78 m·s-2. This trend was also observed when comparing performance between the different 10-min periods. The 5th period (period 40-50 min) was the one that showed differences with respect to the previous ones. Adolescent handball players showed lower levels of exercise intensity, assessed by both time-motion and HR data, in the second half of matches, especially in the middle of this period.

Key words

  • Global Positioning System
  • total distance
  • accelerations
  • decelerations
  • sprint
Open Access

Preliminary Validation of Mirrored Scales for Monitoring Professional Soccer Training Sessions

Published Online: 31 Mar 2020
Page range: 265 - 278

Abstract

Abstract

We aimed to create a single subjective method to assess both internal training loads and subsequent fatigue. This new training-fatigue (dose-response) scale (TFS) was composed of two similar scales with the same properties, metrics and construction criteria. These two scales were designed to rate the perceived exertion (RPETFS) and perceived fatigue (RPFTFS) in professional soccer players. Twenty-two athletes participated to establish reliability, and 15 participated to establish validity. For reliability, the intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were used. For criterion validity, the Spearman’s correlation coefficient and linear regression analyses were applied. Associations between RPETFS and RPFTFS were verified by a chi square test, and a further factorial exploratory analysis was conducted. RPETFS and RPFTFS were found to be reliable (ICC 0.74 and 0.77, SEM 0.30 and 0.30, respectively) and valid. RPETFS was best explained by the internal load of the Banister training impulse (p < 0.001), while RPFTFS was best explained by the internal load of the Stagno training impulse (p < 0.001). An association was found between the scales (RPETFS and RPFTFS) in which training duration had a more substantial impact on these subjective perceptions than did training intensity (p < 0.01). RPETFS and RPFTFS scales are reliable and valid for monitoring training sessions in Brazilian professional soccer players. The simultaneous oscillations of the RPETFS and RPFTFS scores can be used by staff members to better plan weekly training programs based on dose-response ratings. Finally, training duration must be carefully controlled because it has a greater impact than intensity on subjective perceptions.

Key words

  • soccer
  • rating of perceived exertion
  • training impulse
  • recovery
  • ordinal subjective scales
Open Access

Application of Individualized Speed Zones to Quantify External Training Load in Professional Soccer

Published Online: 31 Mar 2020
Page range: 279 - 289

Abstract

Abstract

This study aimed to examine the interchangeability of two external training load (ETL) monitoring methods: arbitrary vs. individualized speed zones. Thirteen male outfield players from a professional soccer team were monitored during training sessions using 10-Hz GPS units over an 8-week competitive period (n = 302 observations). Low-speed activities (LSA), moderate-speed running (MSR), high-speed running (HSR) and sprinting were defined using arbitrary speed zones as <14.4, 14.4–19.8, 19.8–25.1 and ≥25.2 km·h-1, and using individualized speed zones based on a combination of maximal aerobic speed (MAS, derived from the Yo-yo Intermittent recovery test level 1), maximal sprinting speed (MSS, derived from the maximal speed reached during training) and anaerobic speed reserve (ASR) as <80% MAS, 80–100% MAS, 100% MAS or 29% ASR and ≥30% ASR. Distance covered in both arbitrary and individualized methods was almost certainly correlated in all speed zones (p < 0.01; r = 0.67-0.78). However, significant differences between methods were observed in all speed zones (p < 0.01). LSA was almost certainly higher when using the arbitrary method than when using the individualized method (p < 0.01; ES = 5.47 [5.18; 5.76], respectively). Conversely, MSR, HSR and sprinting speed were higher in the individualized method than in the arbitrary method (p < 0.01; ES = 5.10 [4.82; 5.37], 0.86 [0.72; 1.00] and 1.22 [1.08; 1.37], respectively). Arbitrary and individualized methods for ETL quantification based on speed zones showed similar sensitivity in depicting player locomotor demands. However, since these methods significantly differ at absolute level (based on measurement bias), arbitrary and individualized speed zones should not be used interchangeably.

Key words

  • global positioning systems
  • fitness
  • performance
  • testing
26 Articles

Section I – Kinesiology

Open Access

Effects of Lower Extremity Muscle Fatigue on Knee Loading During a Forward Drop Jump to a Vertical Jump in Female Athletes

Published Online: 31 Mar 2020
Page range: 5 - 13

Abstract

Abstract

The aim of this study was to examine changes in the kinematic and kinetic parameters of female athletes performing a forward drop jump to a vertical jump under muscle fatigue condition. Twelve female college athletes performed a forward drop jump to a vertical jump with and without muscle fatigue conditions. A motion capture system and two AMTI force plates were used to synchronously collect kinematic and kinetic data. Inverse dynamics were implemented to calculate the participant’s joint loading, joint moment, and energy absorption. A paired sample t-test was used to compare statistical differences between pre-fatigue and post-fatigue conditions (α = .05). The forward trunk lean angle at initial foot contact, as well as the knee range of motion, total negative work and energy absorption contribution of the knee joint during the landing phase were significantly decreased under post-fatigue condition. The increased peak vertical ground reaction force and peak tibial anterior shear forces were also found under post-fatigue condition. These results indicated that muscle fatigue caused participants to change their original landing posture into stiff landing posture and decrease the energy absorption ability, which increased the tibial anterior shear forces. Therefore, female athletes should appropriately increase the knee flexion angle under muscle fatigue condition to reduce the risk of anterior cruciate ligament injuries.

Key words

  • energy absorption contribution
  • anterior cruciate ligament
  • joint moment
Open Access

Kinematic Analyses of Parkour Landings From as High as 2.7 Meters

Published Online: 31 Mar 2020
Page range: 15 - 28

Abstract

Abstract

Developing effective landing strategies has implications for both injury prevention and performance training. The purpose was to quantify the kinematics of Parkour practitioners’ landings from three heights utilizing four techniques. Seventeen male and three female Parkour practitioners landed from 0.9, 1.8, and 2.7 m utilizing the squat, forward, roll, and stiff landing techniques when three-dimensional kinematics were collected. The stiff landing demonstrated the shortest landing time, and the roll landing showed the longest landing time for 1.8 and 2.7 m. Roll landings demonstrated the greatest forward velocities at initial contact and at the end of the landing. Stiff landings showed the greatest changes in vertical velocity during the early landing, while roll landings showed the least changes for 0.9 and 1.8 m. Both roll and stiff landings generally resulted in decreased changes in horizontal velocity during the early landing compared to squat and forward landings. The four landing techniques also demonstrated different lower extremity joint angles. Stiff landings may increase injury risk because of the quick decrease of vertical velocities. Roll landings allow individuals to decrease vertical and horizontal velocities over a longer time, which is likely to decrease the peak loading imposed on the lower extremities.

Key words

  • jump-landing
  • impact
  • injury
  • performance
  • lower extremities
Open Access

Movement Variability During the Flight Phase in a Single Back Sideflip (Wildcat) in Snowboarding

Published Online: 31 Mar 2020
Page range: 29 - 38

Abstract

Abstract

Understanding the structure and variability of motion is essential for sports technique development and an effective training design. Biomechanical analysis is particularly important in new disciplines with spatially complex motions, such as snowboarding. This study aimed to evaluate the level of variability of the kinematic variables in a single backside snowboard flip known as a “wildcat”. Forty-six correct flips performed by 7 experienced athletes (age: 24.9 ± 4.34 year; body mass: 71.6 ± 12.87 kg; body height: 177.4 ± 6.99 cm) were recorded using an optoelectronic VICON system in the controlled setting of an indoor freestyle park. Athletes were equipped with special boards with wheels and the geometry of the ramps corresponded to the actual on-snow conditions. The analysis revealed two distinct single flip strategies, which differed in the way the tuck position was sustained. For all the measured variables, the coefficient of variation was computed, which allowed to identify the athlete with the highest (average 45.3%) and lowest (average 20.5%) variability of kinematic variables. Moreover, it was shown that the lowest values of the coefficient of variation occurred at the end of the grouping phase (average 14%) and that among all the different variables, those related to the duration of motion were most unstable (average 63%, SD = 48.5%).

Key words

  • snowboarding
  • sports technique
  • movement variability
  • motion capture
Open Access

How do Amateur Endurance Runners Alter Spatiotemporal Parameters and Step Variability as Running Velocity Increases? A Sex Comparison

Published Online: 31 Mar 2020
Page range: 39 - 49

Abstract

Abstract

This study aimed to analyse the effects of running velocity on spatiotemporal parameters and step variability in amateur endurance runners, according to sex. A group of 51 males and 46 females performed an incremental running test on a treadmill (10-16 km/h). Spatiotemporal parameters (contact and flight time, step length, step frequency and step angle [CT, FT, SL, SF, SA]) and step variability, in terms of within-participant standard deviation (SD), were recorded through the OptoGait System. The ANOVA showed significant differences in the magnitude of the spatiotemporal parameters as running velocity increased (p < 0.001). It also revealed significant differences in step variability (p < 0.005) over the entire running protocol. Between-sex differences in CT, SL, SL-normalized and SF (p < 0.05, ES = 0.4-0.8) were found. Differences were also found in step variability at high velocities (15-16 km/h), with males showing a greater SD than females. In conclusion, increasing running velocity makes CT shorter, FT and SL longer, and SF and SA greater in amateur endurance runners, changing step variability, regardless of sex. Additionally, some between-sex differences were found in spatiotemporal parameters and step variability.

Key words

  • gender
  • biomechanics
  • kinematics
  • running
Open Access

Muscle Recruitment Pattern of The Hamstring Muscles in Hip Extension and Knee Flexion Exercises

Published Online: 31 Mar 2020
Page range: 51 - 59

Abstract

Abstract

We aimed to compare dynamic exercise performance between hip extension exercises with different knee angles and between knee flexion exercises with different hip angles, and to investigate the recruitment pattern of the hamstrings in each exercise. Seven men performed 4 isokinetic exercises (3 maximal concentric contractions at 30°/s (peak torque) and 30 maximal concentric contractions at 180°/s (total work)): hip extension with the knee fully extended (HEke) and with the knee flexed at 90° (HEkf) and knee flexion with the hip fully extended (KFhe) and with the hip flexed at 90° (KFhf). The recruitment pattern of the hamstrings was evaluated in each exercise using magnetic resonance imaging (T2 calculation). The HEke condition showed significantly greater peak torque than the HEkf condition (p < 0.05). The KFhf condition had significantly greater peak torque and total work values than the KFhe condition (p < 0.05). Although the biceps femoris long head, semitendinosus, and semimembranosus had significantly increased post-exercise T2 values in the HEke (p < 0.05), KFhe, and KFhf conditions (p < 0.01), the T2 increase values were significantly greater under the KFhf than the HEke condition (p < 0.05). The semitendinosus showed a significantly greater T2 increase value than other muscles under both KFhe and KFhf conditions (p < 0.05). Performance of hip extension and knee flexion exercises increases when the hamstring muscles are in a lengthened condition. The hamstring muscles (particularly the semitendinosus) are more involved in knee flexion than in hip extension.

Key words

  • magnetic resonance imaging
  • T2 relaxation time
  • isokinetic exercise
  • biceps femoris
  • semitendinosus
  • semimembranosus
Open Access

The Transition from Underwater to Surface Swimming During the Push-off Start in Competitive Swimmers

Published Online: 31 Mar 2020
Page range: 61 - 67

Abstract

Abstract

The objective of the present study was to analyze (based on gender and the style of swimming) the kinematic parameters of the transition phase between underwater swimming and surface swimming after the push-off start in competitive national swimmers. Seventy-four swimmers participating in the Spanish Swimming Championships were filmed and analyzed by DLT-2D photogrammetry during the start with the push-off in crawl, backstroke and butterfly styles. Between genders there were small differences in the distance and speed of transition. The male swimmers travelled greater distances (0.84 ± 0.04 vs. 0.66 ± 0.04 m, η2 = 0.05, F = 10.34, p < 0.001) and they were faster (1.59 ± 0.03 vs. 1.38 ± 0.03 m/s, η2 = 0.08, F = 19.54, p < 0.001) in the transition phase than female swimmers. Among styles there were greater differences in time (η2 = 0.47, F = 94.50, p < 0.001) and transition distance (η2 = 0.38, F = 67.08, p < 0.001), than in speed (η2 = 0.05, F = 5.63, p < 0.001). During the backstroke push-off, swimmers spent more time (0.88 ± 0.04 s) and distance (1.17 ± 0.05 m), this being the slowest style (1.37 ± 0.04 m/s). In butterfly, athletes used less time (0.26 ± 0.03 s) and distance (0.39 ± 0.05 m) whereas crawl was the fastest of all (1.57 ± 0.04 m/s). These results allow the phase of transition from underwater to surface swimming to be characterized and to provide useful data for competitive swimmers and coaches to improve performance.

Key words

  • biomechanics
  • kinematics
  • performance
  • direct linear transformation
  • 2D

Section II – Exercise Physiology & Sports Medicine

Open Access

Effects of Oral Branched‐Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise

Published Online: 31 Mar 2020
Page range: 69 - 78

Abstract

Abstract

The aim of this study was to investigate the effects of oral branched-chain amino acids (BCAAs) intake on muscular (creatine kinase and myoglobin) and central (serotonin) fatigue during an incremental exercise protocol and to determine the time to exhaustion. Sixteen male long-distance runners (25.7 ± 2.0 yrs) performed two trials, 14 days apart. Using a double-blind, placebo-controlled, randomised crossover design, participants ingested either 20 g of BCAAs (BCAA trial) or a placebo 1 hour prior to performing an incremental exercise session on a treadmill. The starting speed was 8 km/h and this was increased by 1 km/h every 5 minutes until volitional exhaustion. Blood analysis indicated that plasma levels of serotonin were lower in the BCAA trial (259.3 ± 13.5 ng/ml) than the placebo trial (289.1 ± 14.5 ng/ml) (p < 0.05). There was a similar pattern of results for free fatty acid (p < 0.05). The creatine kinase level was higher in the BCAA trial (346.1 ± 33.7 U/L) than the placebo trial (307.3 ± 30.2 U/L). No significant difference between trials was observed regarding the level of myoglobin (p = 0.139). Time to exhaustion was longer in the BCAA trial (50.4 ± 2.3 min) than the placebo trial (46.6 ± 3.2 min). In conclusion, oral intake of 20 g of BCAAs 1 hour prior to an incremental treadmill exercise session increased time to exhaustion, probably due to the reduction in serotonin concentration. As myoglobin levels were within the normal range in both trials, we conclude that the participants did not reach muscular fatigue.

Key words

  • Serotonin
  • free fatty acid
  • endurance exercise
  • myoglobin
Open Access

Analysis of Polymorphic Variants of the Dopamine Transporter (DAT1) Gene Polymorphism and Personality Traits Among Athletes

Published Online: 31 Mar 2020
Page range: 79 - 89

Abstract

Abstract

Personality traits, especially in sport are modulatory factors of athletes’ behavior – his/ her conscientiousness, the will to achieve an aim, perseverance and motivation of activity. Not only are biological predispositions related to anatomical or biochemical traits of success, but they are also largely determined by personality traits that result from genetic factors. In our research we joined tests of athlete’s personality in correlation with genotypes of the dopamine transporter (DAT1) gene polymorphism. The selection of this polymorphism was based on previous reports connecting the influence of dopamine with motivation and numerous arguments supporting its correlation with human behavior. We observed significant differences among polymorphisms DAT 9/9, 9/10, 10/10 in terms of proportion of particular genotypes between athletes and the control group. We also found significant differences in the NEO FFI sten scale for conscientiousness. We noticed that anxiety was related with genotypic variants of DAT1, specifically the 9/10 VNTR variant, which conditioned lower levels of anxiety in the group of tested athletes. By contrast, the lower sten value of agreeability was statistically significant for the group of athletes that were carriers of the 10/10 VNTR genotype. Heterozygous 9/10 VNTR among athletes showed lower levels of anxiety in comparison with the control group, whereas agreeability determined using the NEO FFI scale represented a lower value among athletes that had the 10/10 polymorphism. We may thus conclude that the presence of polymorphic variants of the dopamine transporter gene corresponds to athletes’ personality traits.

Key words

  • dopamine
  • personality
  • athletes
Open Access

Physical and Physiological Response to Different Modes of Repeated Sprint Exercises in Basketball Players

Published Online: 31 Mar 2020
Page range: 91 - 99

Abstract

Abstract

The aim of this study was to investigate changes in physical and physiological responses to different modes of repeated sprint exercise by measuring speed, total time (sum of sprints), fatigue index, heart rate, local oxygen saturation, total haemoglobin content, and blood lactate. The volume of the physical load (distance, work and rest ratio) was the same in both exercises, but load specifics were different. The first mode consisted of 10 x 30 m sprints (with one change of direction) interspersed with 30 s of passive recovery, while the second mode of 20 x 15 m shuttle sprints interspersed with 15 s of passive recovery. Both exercise modalities were repeated three times with a five-minute rest interval between bouts with 7 days of recovery between each testing condition. Twelve highly trained male basketball players volunteered to participate in this study. Our study showed that different modes of repeated sprint exercises elicited a different physical response and metabolic demand. Longer sprints with directional changes placed a higher demand on the anaerobic glycolytic system compared to straight and more frequent sprint exercises. However, players’ fatigue was more noticeable in shorter and more frequent sprints. Heart rate responses and local use of O2 showed a similar activity of aerobic reactions through the different exercises. During the sprints, players’ SmO2 fell to 40% and recovered to the level of about 80% during passive rest intervals without showing differences in both modalities. This suggests that both types of sprint exercises can similarly stimulate aerobic metabolism.

Key words

  • local oxygen saturation
  • blood lactate
  • heart rate
  • speed
  • fatigue index
Open Access

The Impact of Aspirin Intake on Lactate Dehydrogenase, Arterial Stiffness, and Oxidative Stress During High‐Intensity Exercise: A Pilot Study

Published Online: 31 Mar 2020
Page range: 101 - 113

Abstract

Abstract

Aspirin is a common nonsteroidal anti-inflammatory drug used to reduce fever, pain, and inflammation. However, aspirin’s anti-inflammatory properties may also prevent increased levels of blood lactate dehydrogenase, vascular arterial stiffness and oxidative stress induced by high-intensity exercise. The purpose of this study was to investigate the effects of 4 weeks of aspirin supplementation on lactate dehydrogenase activity, lactate, arterial stiffness, and antioxidant capacity during high-intensity exercise in Taekwondo athletes. Participants were randomly divided into two groups: aspirin supplementation (n = 10) and placebo-control (n = 10). Blood levels of lactate dehydrogenase (LDH) enzyme activity and lactate were assessed to examine muscle damage and carotid-to-radial pulse wave velocity and the augmentation index were measured to examine arterial stiffness. Blood levels of superoxide dismutase, malondialdehyde, and glutathione peroxidase were assessed to determine antioxidant capacity and levels of oxidative stress. There were significant group × time interactions for enzyme activity of LDH (Δ-60 ± 24.36 U/L) and carotid-to-radial pulse wave velocity (Δ-1.33 ± 0.54 m/s), which significantly decreased (p < 0.05) following aspirin supplementation compared to placebo-control. Superoxide dismutase (Δ359 ± 110 U/gHb) and glutathione peroxidase (Δ28.2 ± 10.1 U/gHb) significantly decreased while malondialdehyde (0Δ3.0 ± 0.1 mmol/mL) significantly increased (p < 0.05) in the placebo-control group compared to the supplementation group. However, there were no changes in lactate concentration levels or augmentation index. These results reveal that low-dose aspirin supplementation would be a useful supplementation therapy to prevent high-intensity exercise training-induced increases in oxidative damage, inflammation, skeletal muscle fatigue, and arterial stiffness in elite Taekwondo athletes.

Key words

  • antioxidant capacity
  • high-intensity training
  • NSAID
  • pulse wave velocity
Open Access

Effects of an Exogenous Ketone Supplement on Five‐Kilometer Running Performance

Published Online: 31 Mar 2020
Page range: 115 - 127

Abstract

Abstract

Numerous oral ketone supplements are marketed with the claim that they will rapidly induce ketosis and improve exercise performance. The purpose of this study was to assess exercise performance time and related physiological, metabolic and perceptual responses of recreational endurance runners after ingestion of a commercially available oral ketone supplement. Recreational endurance runners (n = 10; age: 20.8 ± 1.0 years; body mass: 68.9 ± 5.6 kg; height: 175.6 ± 4.9 cm) participated in a double-blind, crossover, repeated-measures study where they were randomized to 300 mg.kg-1 body weight of an oral β-hydroxybutyrate-salt + Medium Chain Triglyceride (βHB-salt+MCT) ketone supplement or a flavor matched placebo (PLA) 60 min prior to performing a 5-km running time trial (5KTT) on a treadmill. Time, HR, RPE, affect, RER, VO2, VCO2, and VE were measured during the 5-km run. The Session RPE and affect (Feeling Scale) were obtained post-5KTT. Plasma glucose, lactate and ketones were measured at baseline, 60-min post-supplement, and immediately post-5KTT. Plasma R-βHB (endogenous isomer) was elevated from baseline and throughout the entire protocol under the βHB-salt+MCT condition (p < 0.05). No significant difference (58.3 ± 100.40 s; 95% CI: -130.12 – 13.52; p = 0.100) was observed between the βHB-salt+MCT supplement (1430.0 ± 187.7 s) and the PLA (1488.3 ± 243.8 s) in time to complete the 5KTT. No other differences (p > 0.05) were noted in any of the other physiological, metabolic or perceptual measures.

Key words

  • ketosis
  • beta-hydroxybutyrate
  • dietary supplements
  • ergogenic aid
Open Access

What are the Limiting Factors During an Ultra‐Marathon? A Systematic Review of the Scientific Literature

Published Online: 31 Mar 2020
Page range: 129 - 139

Abstract

Abstract

This review aimed to analyse factors that limited performance in ultra-marathons and mountain ultra-marathons. A literature search in one database (PubMed) was conducted in February 2019. Quality of information of the articles was evaluated using the Oxford´s level of evidence and the Physiotherapy Evidence Database (PEDro) scale. The search strategy yielded 111 total citations from which 23 met the inclusion criteria. Twenty one of the 23 included studies had a level of evidence 2b (individual cohort study), while the 2 remaining studies had a level of evidence of 5 (expert opinion). Also, the mean score in the PEDro scale was 3.65 ± 1.61, with values ranging from 0 to 7. Participants were characterised as experienced or well-trained athletes in all of the studies. The total number of participants was 1002 (893 men, 86 women and 23 unknown). The findings of this review suggest that fatigue in ultra-endurance events is a multifactorial phenomenon that includes physiological, neuromuscular, biomechanical and cognitive factors. Improved exercise performance during ultra-endurance events seems to be related to higher VO2max values and maximal aerobic speed (especially during submaximal efforts sustained over a long time), lower oxygen cost of transport and greater running experience.

Key words

  • trail running
  • VO
  • performance
  • fatigue
  • endurance
Open Access

Heart Rate Variability is Correlated with Perceived Physical Fitness in Elite Soccer Players

Published Online: 31 Mar 2020
Page range: 141 - 150

Abstract

Abstract

Heart Rate Variability (HRV) has been typically used to monitor athletes’ physical fitness readiness. The supine position maximizes parasympathetic tone, which is important for monitoring in continuous aerobic sports, however, this is not the case of team sports that rely on anaerobic intermittent bouts, thus increasing sympathetic activation and vagal withdrawal. We hypothesized that HRV during sympathetic activation and vagal withdrawal would be a useful marker to evaluate perceived physical fitness in team sports. HRV was measured in both supine and standing positions during the mornings of 4 match days in 14 professional players. The supine Root Mean Square of the Successive Differences (RMSSD), as well as spectral analysis indices were recorded. Perceived physical fitness was assessed after each match by means of a visual analogue scale (VAS). Supine RMSSD was moderately correlated with perceived physical fitness (rho = 0.416), however, larger correlations were observed for supine and standing spectral indices (rho > 0.5). Correlation between RMSSD and Total Power was very large, thus questioning the usual interpretation of RMSSD (rho > 0.7). Standing Spectral HRV analyses may be a useful method for evaluating perceived physical fitness in the context of team sports. RMSSD may reflect the overall variability of HR and not only the parasympathetic influence, as observed in the current study.

Key words

  • autonomic nervous system
  • soccer
  • training, intermittent sports
  • orthostatic test

Section III – Sports Training

Open Access

The Effects of the Movement Tempo on the One-Repetition Maximum Bench Press Results

Published Online: 31 Mar 2020
Page range: 151 - 159

Abstract

Abstract

Different tempos of movement can be used during resistance training, but programming them is often a trial-and-error practice, as changing the speed at which the exercise is performed does not always correspond with the tempo at which the 1-repetition-maximum occurred. Therefore, the aim of this study was to determine the effect of different movement tempos during the bench press (BP) exercise on the one-repetition maximum (1RM) load. Ninety men (age = 25.8 ± 5.3 years, body mass = 80.2 ± 14.9 kg), with a minimum one year of resistance training experience took part in the study. Using a randomized crossover design, each participant completed the BP 1RM test with five different movement tempos: V/0/V/0, 2/0/V/0, 5/0/V/0, 8/0/V/0 and 10/0/V/0. Repeated measures ANOVA compared the differences between the 1RM at each tempo. The 1RM load was significantly greater during V/0/V/0 and 2/0/V/0 compared to 5/0/V/0, 8/0/V/0, and 10/0/V/0 (p < 0.01). Furthermore, the 1RM load was significantly greater during 5/0/V/0 compared to 8/0/V/0 and 10/0/V/0 (p < 0.01), but there were no differences between either V/0/V/0 and 2/0/V/0 (p = 0.92) or between 8/0/V/0 and 10/0/V/0 (p = 0.08). Therefore, different movement tempos used during training should be accompanied by their own tempo-specific 1RM testing, as slower eccentric phases significantly decrease maximal concentric performance. Furthermore, 1RM test procedures should include information about the movement tempo used during the test protocol. In addition, the standardization of the tempo should be taken into account in investigations that use the 1 RM test to assess the effects of any treatment on maximal muscle strength.

Key words

  • eccentric movements
  • duration of repetition
  • maximal strength
  • external load
  • resistance training
Open Access

Acute Effects of a Static vs. a Dynamic Stretching Warm-up on Repeated-Sprint Performance in Female Handball Players

Published Online: 31 Mar 2020
Page range: 161 - 172

Abstract

Abstract

This randomized cross-over study examined the effects of typical static and dynamic stretching warm-up protocols on repeated-sprint performance. Thirteen young female handball players performed a 5 min aerobic warm-up followed by one of three stretching protocols for the lower limbs: (1) static stretching, (2) dynamic-ballistic stretching, and (3) no stretching before performing five all-out sprints on a cycle ergometer. Each protocol was performed on a different occasion, separated by 2-3 days. Range of movement (ROM) was also measured before and after the warm-up protocols with a sit-and-reach test. Fixed and random effects of each stretching protocol on repeated sprint performance were estimated with mixed linear modeling and data were evaluated via standardization and magnitude-based inferences. In comparison to no stretching, there were small increases in ROM after dynamic stretching (12.7%, ±0.7%; mean, ±90% confidence limits) and static stretching (19.2%, ±0.9%). There were small increases in the average power across all sprints with dynamic stretching relative to static stretching (3.3%, ±2.4%) and no stretching (3.0%, ±2.4%) and trivial to small increases in the average power in the 1st and 5th trials with dynamic stretching compared to static stretching (3.9%, ±2.6%; 2.6%, ±2.6%, respectively) and no stretching (2.0%, ±2.7%; 4.1%, ±2.8%, respectively). There were also trivial and small decreases in power across all sprints with static relative to dynamic stretching (-1.3%, ±2.8%) and no stretching (-3.5%, ±2.9%). Dynamic stretching improved repeated-sprint performance to a greater extent than static stretching and no stretching.

Key words

  • performance
  • team sport athletes
  • high-intensity
  • modeling
Open Access

The Relative Age Effect in Professional Futsal Players

Published Online: 31 Mar 2020
Page range: 173 - 183

Abstract

Abstract

The objective of this study was to verify the occurrence and effect size of relative age effect in professional futsal players, by observing how its presence and impact change according to the season, team level and player position. The sample was composed of 1873 professional futsal players who played in the First Division of the Spanish National Futsal League between seasons 2006-2007 and 2014-2015. The players’ birthdates were divided into quarters (Q1, Q2, Q3 and Q4). A relative age effect reversal was observed in the professional futsal players for the nine analyzed seasons. A relative age reversal effect was observed in high and medium level teams. Finally, a relative age effect reversal was also found for the goalkeeper and pivot positions. The results could suggest that players that initially experienced maturity disadvantages in major sports, can have a second chance to emerge in professional minor sports (i.e. futsal vs. soccer). However, the underlying mechanisms why a reversal occurs are still unclear, and more studies focusing on the mediators of the effect are needed.

Key words

  • talent development
  • performance analysis
  • team level
  • playing position
  • team sport
Open Access

Quantification of Movement Characteristics in Women’s English Premier Elite Domestic Rugby Union

Published Online: 31 Mar 2020
Page range: 185 - 194

Abstract

Abstract

This study aims were to determine the positional physical requirements of English domestic women’s rugby union match-play. Global positioning system data (Catapult Minimax S4) were collected at 10 Hz of 129 competitive player games from the Tyrrells Premier15 league. Players were classified according to broad (Forwards, Backs) and specific positions (front-, second-, back-row, scrum-half, inside-, and outside-backs). Total distances, maximum speed, and player loads were calculated. Mean total distance was 4982 m and was similar between the Forwards and Backs, with second-row players covering the most (5297 m) and outside-backs the least (4701 m). Inside- and outside-backs covered a significantly greater distance at high speed running (134 m; 178 m) and sprinting (74 m; 92 m) speeds, respectively, whereas the second- and back-row covered greater distances jogging (1966 m; 1976 m) and the front-row spent the greatest overall distance walking (2613 m). Outside-backs reached greater maximum speed than all other positions (24.9 km.h-1). The mean player load was highest in the back-row (562 AU) and second-row (555 AU) and these were higher than the outside-backs (476 AU). These findings indicate that the demands placed on female rugby players are position specific and differ from male players. Additionally, the data are the first obtained from the 10 Hz GPS and from within English domestic women’s rugby, thus adding to the overall limited data available on women’s rugby union.

Key words

  • movement patterns
  • workload
  • Global Positioning System
  • positional demands
Open Access

Relative Age Effect in the Girls’ Volleyball U18 World Championship

Published Online: 31 Mar 2020
Page range: 195 - 202

Abstract

Abstract

The relative age effect (RAE), within the sporting scope, refers to the possible advantages of participation and performance of athletes born in the first months of the year of selection in relation to others within the same age category. The aim of the present study was to investigate the RAE in girls’ volleyball players participating in the U-18 World Championship, analysing the differences between the medal teams and other teams in the tournament, and considering this phenomenon in relation to the continents. Data collection was obtained from the website of the International Volleyball Federation with a sample made of 1654 youth players in the last six world championships (2007, 2009, 2011, 2013, 2015 and 2017). A greater representation of athletes born in the first months of the year of all the world championships was observed. In the comparison among the continents, it was observed that in Africa, there was a more equal distribution of quartiles compared to America, Asia and Europe. It should be noted that there was a higher percentage of medalist athletes born at the beginning of the year in comparison to the countries that placed in the last three positions of the championship. Therefore, in U-18 female volleyball, there is an advantage to have the closest birth age at the beginning of the competitive biennium.

Key words

  • youth
  • volleyball
  • birth date
  • player selection
  • age effect
Open Access

Water Polo Shooting Performance: Differences Between World Championship Winning, Drawing and Losing Teams

Published Online: 31 Mar 2020
Page range: 203 - 214

Abstract

Abstract

Shooting performance of globally ranked winning, drawing and losing water polo teams was compared, and technical and tactical success indicators were identified. In total, 886 shots from a world championship final round were videotaped and teams were clustered for a performance evaluation (considering differences between game outcomes). Shooting speeds were assessed by a radar, with higher values observed at further distances from the goal than in the central area close to the goal (p ≤ 0.00, ES: 2.54). Shots tended to be more frequent from the central corridor, with ≤50% and >75% relative shot efficacy attained from field areas 3 and 6; winning teams obtained better results. Furthermore, winners had greater success than losers when shooting from field area 2 (p ≤ 0.04, ES: 1.13) and towards the goal zone 2 (p < 0.03, ES: 1.10). They also attained better efficacy regarding shots towards goal zone 1, had better efficacy on the part of centre-forwards (p ≤ 0.05, ES: 0.85-1.27), and were more effective regarding shots without a frontal defensive block. In addition, contingency analysis highlighted shots performed from field area 6, without a defensive block, toward the bottom left goal corner, and through man-up play as success indicators (all for p ≤ 0.005). We concluded that world-level winning teams homogeneously distributed their shot opportunities at the second offensive line with balanced efficacy, creating variability and uncertainty in their opponents’ defensive action. Elite level players must be capable of interpreting game situations with intelligence and proper decision making. This information may be useful for improving teams performance.

Key words

  • match analysis
  • performance indicators
  • expert teams
  • success
Open Access

Match Performance Indicators that Discriminated Between Winning, Drawing and Losing Teams in the 2017 AFCON Soccer Championship

Published Online: 31 Mar 2020
Page range: 215 - 221

Abstract

Abstract

The purpose of this study was to examine match performance indicators that discriminated between winning, drawing and losing teams in the 2017 Total Africa Cup of Nations (AFCON) soccer championship. Data were collected from 32 matches during the AFCON soccer tournament using the InStat® system. The studied variables included the number of goals scored, the time period in which a goal was scored and the impact of the first goal on the match outcome, as well as total shots, shots on goal, total passes, accurate passes, corners, ball possession, fouls, offsides as well as yellow and red cards. The results showed that goals scored (1.80 ± 0.83), total shots (11.05 ± 4.83), shots on target (4.70 ± 2.62), fouls (18.60 ± 5.19), offsides (2.35 ± 1.76), yellow cards (1.55 ± 1.10), and red cards (0.05 ± 0.22) were discriminative performance indicators of winning teams. In contrast, losing teams yielded higher mean values in total passes (260.30 ± 49.10), accurate passes (69.28 ± 5.74), corners (5.10 ± 2.95), and ball possession (51.20 ± 5.52). In conclusion, these results have practical implications for coaches in planning and implementing team tactics for successful performance.

Key words

  • performance
  • game-related statistics
  • goals
  • team sports
Open Access

Activity of Trunk and Lower Extremity Musculature: Comparison Between Parallel Back Squats and Belt Squats

Published Online: 31 Mar 2020
Page range: 223 - 228

Abstract

Abstract

The back squat is widely used in strength training programs. Alternatively, the belt squat has been gaining popularity since it loads the weight on the hips, as opposed to the shoulders and spine. The purpose of this study was to determine whether using a belt squat would result in less lumbar extensor activation while providing similar excitation of other prime mover and stabilizer musculature. Ten participants (9 males, 1 female; age 29.3 ± 4.9 years; body mass 96.2 ± 17.8 kg) who regularly trained both belt squats and back squats performed three sets of 5 repetitions with 100% bodyweight for each exercise. Peak and integrated muscle activity was calculated and normalized to a maximum voluntary isometric contraction. A one-way ANOVA (p < 0.05) was used to compare conditions. Belt squatting decreased lumbar erector impulse (45.4%) and peak (52.0%) activation as compared to the back squat. Belt squatting did not alter activation of the lower extremities except for a decrease in the gluteus maximus (35.2% impulse and 32.1% peak), gluteus medius (54.1% impulse and 55.2% peak). Furthermore, belt squatting reduced activation of the rectus abdominus (44.3% impulse; 31.1% peak), and external obliques (45.8% impulse; 53.7% peak) as compared to back squatting. Our results suggest belt squatting provides similar muscular demands for the quadriceps, hamstrings, and plantar flexors, but is less demanding of trunk stabilizers, and gluteual muscles. Belt squats may be a suitable alternative to back squats in order to avoid stressing low back or trunk musculature.

Key words

  • low back
  • resistance training
  • EMG
Open Access

Assessing Change of Direction Ability in a Spanish Elite Soccer Academy

Published Online: 31 Mar 2020
Page range: 229 - 239

Abstract

Abstract

The aims of the study were: a) to analyze the reproducibility of the Modified Agility Test (MAT) according to two types of displacement (i.e. constrained [MATtop] vs. free [MATfree]), b) to examine the explanatory capacity of anthropometric characteristics and neuromuscular performance on the ability to change the direction (CODA), c) to look into the practical consequences of the types of displacement from the perspective of an elite soccer academy. 118 male soccer players (age: 16 (13-25) years old) from the same elite Spanish soccer academy (U13 to senior) were tested twice on two versions of the MAT (MATtop and MATfree), with 48 hours between testing sessions. Moreover, they were tested on linear-sprint performance, over 5 m (S5m) and 15 m (S15m), and the vertical jump (VJ) (countermovement jump with [ACMJ] and without an arm swing [CMJ]). The main findings were: a) the type of displacement did not affect the reliability of the CODA test; b) weight, S15m, ACMJ and CMJ variables explained close to 60% of CODA performance; c) MATtop (i.e. constrained displacement) and MATfree (i.e. free-displacement) CODA tests could show different profiles of development along the age groups; and d) the impact of the task’s constraints was relatively higher in U16 and U17 groups. CODA seems to have a variable meaning depending on the characteristics of the test and the age of the participants.

Key words

  • agility
  • test
  • youth
  • soccer
  • athletics
Open Access

Making Decisions and Motor Actions with Technical Biomechanical Classifications in Male Judo Weight Categories

Published Online: 31 Mar 2020
Page range: 241 - 252

Abstract

Abstract

The aim of the study was to compare motor action variables of judo combat phases and technical biomechanical assessment of the seven weight categories. The sample was composed of 638 bouts (176 of extra lightweight <66 kg, 289 of half lightweight 66 > 73 kg, 180 of lightweight 73 > 81 kg, 244 of half middleweight 81 > 90 kg, 174 of middleweight 81 > 90 kg, 151 of half heavyweight 90 > 100 kg and 142 of heavyweight >100 kg) during motor actions of approach, gripping, attack, defense and groundwork combat phases, verifying the interactions between them by Markov chains and comparisons by Kruskall-Wallis and Dunn post hoc tests (p ≤ .05). The results demonstrated that lighter weight categories showed higher approach phases than the heavyweight category, and the lightweight group demonstrated higher defensive action frequencies than the half lightweight category and heavyweight athletes. Heavyweight and middleweight categories demonstrated higher groundwork combat frequencies than lighter weights, and the heavyweight category showed higher pause frequencies than the lightweight category. Regarding the decision-making model, the main transitions presented by the Markov chains showed higher prevalence of the following combinations: gripping occurring before the lever and length attacks, lever attack followed by the length attack, and length attack occurring earlier than the groundwork phase.

Key words

  • martial arts
  • biomechanics
  • performance analysis
  • motor control
  • time motion analysis
  • circuit-based exercise
Open Access

Physical and Physiological Demands During Handball Matches in Male Adolescent Players

Published Online: 31 Mar 2020
Page range: 253 - 263

Abstract

Abstract

This study aimed to describe the physical and physiological demands of adolescent handball players and compare movement analysis and exercise intensities between the first and second halves and between the different periods of the match. Fourteen adolescent handball players (age 15.7 ± 0.8 years, body mass: 65.6 ± 3.4 kg, body height: 169.5 ± 3.9 cm), played two friendly matches, in which no substitutions were made. The analysis was carried out with a Global Positioning System technology. The following physical variables were analyzed: Total distance covered (TD); distance covered at faster velocities than 18 km·h-1 (TDC>18km·h-1); number of accelerations (Accel) and decelerations (Decel); number of accelerations and decelerations higher than 2.78 m·s-2 (Accel>2.78 m·s-2 and Decel>2.78 m·s-2); number of sprints (Sprints); accelerations interspersed with a maximum of 30 s between them (RAS≤30s) and as a physiological variable the heart rate (HR) was examined. Significant differences (p < 0.01 –p < 0.001) between the first and the second half in all variables mentioned were observed, except in Accel>2.78 m·s-2 and Decel>2.78 m·s-2. This trend was also observed when comparing performance between the different 10-min periods. The 5th period (period 40-50 min) was the one that showed differences with respect to the previous ones. Adolescent handball players showed lower levels of exercise intensity, assessed by both time-motion and HR data, in the second half of matches, especially in the middle of this period.

Key words

  • Global Positioning System
  • total distance
  • accelerations
  • decelerations
  • sprint
Open Access

Preliminary Validation of Mirrored Scales for Monitoring Professional Soccer Training Sessions

Published Online: 31 Mar 2020
Page range: 265 - 278

Abstract

Abstract

We aimed to create a single subjective method to assess both internal training loads and subsequent fatigue. This new training-fatigue (dose-response) scale (TFS) was composed of two similar scales with the same properties, metrics and construction criteria. These two scales were designed to rate the perceived exertion (RPETFS) and perceived fatigue (RPFTFS) in professional soccer players. Twenty-two athletes participated to establish reliability, and 15 participated to establish validity. For reliability, the intraclass correlation coefficient (ICC) and standard error of measurement (SEM) were used. For criterion validity, the Spearman’s correlation coefficient and linear regression analyses were applied. Associations between RPETFS and RPFTFS were verified by a chi square test, and a further factorial exploratory analysis was conducted. RPETFS and RPFTFS were found to be reliable (ICC 0.74 and 0.77, SEM 0.30 and 0.30, respectively) and valid. RPETFS was best explained by the internal load of the Banister training impulse (p < 0.001), while RPFTFS was best explained by the internal load of the Stagno training impulse (p < 0.001). An association was found between the scales (RPETFS and RPFTFS) in which training duration had a more substantial impact on these subjective perceptions than did training intensity (p < 0.01). RPETFS and RPFTFS scales are reliable and valid for monitoring training sessions in Brazilian professional soccer players. The simultaneous oscillations of the RPETFS and RPFTFS scores can be used by staff members to better plan weekly training programs based on dose-response ratings. Finally, training duration must be carefully controlled because it has a greater impact than intensity on subjective perceptions.

Key words

  • soccer
  • rating of perceived exertion
  • training impulse
  • recovery
  • ordinal subjective scales
Open Access

Application of Individualized Speed Zones to Quantify External Training Load in Professional Soccer

Published Online: 31 Mar 2020
Page range: 279 - 289

Abstract

Abstract

This study aimed to examine the interchangeability of two external training load (ETL) monitoring methods: arbitrary vs. individualized speed zones. Thirteen male outfield players from a professional soccer team were monitored during training sessions using 10-Hz GPS units over an 8-week competitive period (n = 302 observations). Low-speed activities (LSA), moderate-speed running (MSR), high-speed running (HSR) and sprinting were defined using arbitrary speed zones as <14.4, 14.4–19.8, 19.8–25.1 and ≥25.2 km·h-1, and using individualized speed zones based on a combination of maximal aerobic speed (MAS, derived from the Yo-yo Intermittent recovery test level 1), maximal sprinting speed (MSS, derived from the maximal speed reached during training) and anaerobic speed reserve (ASR) as <80% MAS, 80–100% MAS, 100% MAS or 29% ASR and ≥30% ASR. Distance covered in both arbitrary and individualized methods was almost certainly correlated in all speed zones (p < 0.01; r = 0.67-0.78). However, significant differences between methods were observed in all speed zones (p < 0.01). LSA was almost certainly higher when using the arbitrary method than when using the individualized method (p < 0.01; ES = 5.47 [5.18; 5.76], respectively). Conversely, MSR, HSR and sprinting speed were higher in the individualized method than in the arbitrary method (p < 0.01; ES = 5.10 [4.82; 5.37], 0.86 [0.72; 1.00] and 1.22 [1.08; 1.37], respectively). Arbitrary and individualized methods for ETL quantification based on speed zones showed similar sensitivity in depicting player locomotor demands. However, since these methods significantly differ at absolute level (based on measurement bias), arbitrary and individualized speed zones should not be used interchangeably.

Key words

  • global positioning systems
  • fitness
  • performance
  • testing

Plan your remote conference with Sciendo