Does Tempo of Resistance Exercise Impact Training Volume?

Development of muscle strength belongs to key components of conditioning in various sports. Scientific studies connected with strength training have mainly analysed such variables as exercise intensity, volume, number of sets, repetitions, duration of rest periods between sets and exercises (Bird et al., 2005; Golas et al., 2017; Kraemer et al., 2002). The effect of these variables on the process of muscle adaptation has been extensively explored and discussed. However, the results are not always unequivocal. Volume and intensity of exercise are the basic components of training loads, having a direct impact on adaptation patterns. Exercise volume during resistance training has been conventionally evaluated as a total number of repetitions performed in each set, regardless of the time and speed of individual exercises. However, one complete repetition may take from a few to more than ten seconds. Studies have found that the external load ranging from 30% 1RM to 95% 1RM results in similar hypertrophy (Burd et al., 2010; Fry, 2004; Mitchell et al., 2012; Wernbom et al., 2007). Therefore, examinations of other variables (such as movement speed) of resistance exercise is needed, because they can significantly influence training adaptations. Despite numerous scientific studies on resistance training, only few have analysed the effects of movement tempo (cadence) on adaptive processes in terms of strength, muscle power or muscle hypertrophy (Hatfield et al., 2006; Headley et al., 2011; Hunter et al., 2003; Keeler et al., 2001; Sakamoto and Sinclair, 2006; Westcott et al., 2001; Golas et al., 2016; Maszczyk et al., 2016; Wilk et al., 2018). The term tempo relates to the rate at which each repetition is performed. Changes in tempo, and consequently, the velocities in particular phases of the movement, can result from the effect of the external resistance, with the increase in the external load leading to the decline in maximal movement speed in the concentric phase (McArdle et al., 2015) or conscious control of individual movement cadences. Cadence is most often defined by means of several digits which correspond to particular movement phases. For example, 4/0/2/0 denotes a 4-second eccentric phase, no break in the transition phase, a 2-second concentric phase and no rest before the next repetition (King, 2002). Each of the forms of resistance training leads to hypertrophy or an increase in muscle strength (Schoenfeld et al., 2017), but training with controlled movement tempo can induce different post-exercise responses and long-term adaptations. A slower movement cadence has been often used to stimulate muscle hypertrophy (Gumucio et al., 2015), since faster uncontrolled speeds are typically employed to develop strength and muscle power (Bird et al., 2005). The number of repetitions performed at a specific tempo impacts total time under tension in a set (TUT_set). TUT provides accurate information about the duration of resistance effort for a set, and in the whole training session (TUT_sum). With a slow movement tempo, especially 5/0/5/0 or even extremely slow 10/0/10/10, performance of a lower number of repetitions in a set takes longer and has longer TUT than for a faster tempo with a higher number of repetitions. In this situation, determination of exercise volume using the number of performed repetitions is not very informative. Table 1 presents simulations of exercise volume in resistance training computed based on the number of performed repetitions and time under tension during a set (TUT_set), and the entire training session (TUT_sum). The simulation demonstrated that performing the highest number of repetitions with a tempo 2/0/2/0 does not mean the longest time under tension, both for a set and the entire training session. Therefore, the greatest number of repetitions does not translate into the longest time under tension.

Table 1

Simulations of exercise volume in resistance training

Studies have found that the lower the movement speed, the more dynamic decline in maximal muscle force (Hutchins, 1993; Kraemer et al., 2002; Westcott et al., 2001). This was confirmed by Headley et al. (2011) who demonstrated that with a fast movement speed, athletes generated a higher level of maximal muscle force compared to the force recorded during slow tempo movements. Similar observations concern the number of repetitions. Sakamoto and Sinclair (2006) demonstrated that faster movement speeds helped perform more repetitions with a specific %RM load. Furthermore, the researchers found that in a group of people who performed exercises with much smaller volume (smaller volume resulted from a lower number of repetitions), but used a slower movement tempo, the post-exercise fatigue was higher, while a greater decline in muscle power was recorded compared to the group that used volitional speeds (Hatfield et al., 2006). Few previous studies have indicated that the protocols with various tempos (cadences) may lead to different post-exercise responses, both acute and chronic. Time under tension in a set (TUT_set) has an effect on the level of post-exercise metabolic and endocrine changes (Bird et al., 2005; Wilk et al., 2018). Extended time of constant muscle tension during a slow movement tempo has a beneficial effect on muscle hypertrophy (Bird et al., 2005; Keogh et al., 1999). There are also scientific reports which have shown that the independent change in cadences in particular phases of movement has an impact on postexercise adaptations. Gumucio et al. (2015) demonstrated that slower cadence in the eccentric phase impacted muscle hypertrophy more than the extension of the concentric phase. More recent research has focused on extremely slow cadences and tempos (Hatfield et al., 2006; Westcott et al., 2001), whereas no studies have analysed more practicable and moderate tempos with variable cadences, both in the eccentric and concentric phases.

The aim of this study was to evaluate the effect of varied tempos i.e. regular (REG) 2/0/2/0, medium (MED) 5/0/3/0 and slow (SLO) 6/0/4/0 during resistance exercise on training volume based on the total number of performed repetitions (REP_sum1-5) and time under tension (TUT_sum1-5). We hypothesized that the change in movement tempo would have a significant effect on TUT and REP independently for individual sets, and on exercise volume (REP_sumi–5), as well as total time under tension (TUT_sum1-5) for the entire experimental training session.

All the data had normal distribution (W ranged between 0.80 and 0.99). Significant differences in TUT (s) were found in particular sets (BP_s1, BP_s2, BP_s3, BP_s4, BP_s5) for each tempo of 2/0/2/0, 5/0/3/0 and /6/0/4/0 (p < 0.001) (Table 2). The ANOVA also revealed substantial differences in the REP for individual sets BP_s1, BP_s2, BP_s3, BP_s4, BP_s5 (p < 0.001) (Table 5). Post-hoc analyses showed that TUT for each set BP_s1, BP_s2, BP_s3, BP_s4, BP_s5 and total TUTsum1-5 were significantly higher in the 5/0/3/0 and 6/0/4/0 tempos compared to 2/0/2/0, which means that 2/0/2/0 differed significantly between 5/0/3/0 and 6/0/4/0 (p < 0.001). Furthermore, the REP was significantly higher in the 2/0/2/0 tempo compared to 5/0/3/0 and 6/0/4/0 in each set (BP_s1, BP_s2, BP_s3, BP_s4, BP_s5) and total REP sum_1–5. TUT and REP between 5/0/3/0 and 6/0/4/0 tempos were not significantly different. It was demonstrated that the participants performed more REP in particular sets (BP_s1, BP_s2, BP_s3, BP_s4, BP_s5) at the 2/0/2/0 tempo (Figure 2), but TUT in all sets (BP_s1, BP_s2, BP_s3, BP_s4, BP_s5) was highest when the 6/0/4/0 tempo was used (Figure 1). All values of TUT and REP for BP_s1, BP_s2, BP_s3, BP_s4, BP_s5 sets were summed and the differences in TUT_sum1-5 and REP_sum1-5 between 2/0/2/0 tempo, 5/0/3/0 and 6/0/4/0 were significant (p < 0.001) (Tables 2 and 4). TUT_sum1-5 and REP_sum1-5 between 5/0/3/0 and 6/0/4/0 were not significantly different.

Table 2

The level and differences in total TUT_sum1-5 for the REG 2/0/2/0, MED 5/0/3/0 and SLOW 6/0/4/0 tempos of movement.

Table 3

The level of differences in TUT for BP_s1 -BP_s5 sets for the REG 2/0/2/0, MED 5/0/3/0 and SLOW 6/0/4/0 tempos of movement.

Table 4

The level and differences in total REP_sum1-5 for the REG 2/0/2/0, MED 5/0/3/0 and SLOW 6/0/4/0 tempos of movement.

Table 5

The level of differences in REP for BP_s1 - BP_s5 sets for the REG 2/0/2/0, MED 5/0/3/0 and SLOW 6/0/4/0 tempos of movement.

Figure 1

Figure 2

The main finding of this study is that the movement tempo in resistance exercise impacts training volume, both in terms of repetitions and total time under tension. The study demonstrated significant differences in TUT_sum1-5 and REP_sum1-5 between REG 2/0/2/0 and MED 5/0/3/0, SLOW 6/0/4/0 tempos, despite using the same %RM and exercise to volitional muscular failure. The highest volumes in the experiment, based on the total number of repetitions REP_sum1-5 was observed for REG (28.32 ± 6.86 REP), whereas the lowest, for the SLOW (15.71 ± 4.03 REP) tempo. Furthermore, the highest TUT_sum1-5 was registered for SLOW (178.8 ± 33.69 REP) i.e. tempo for which the smallest training volume computed from the number of repetitions was obtained. The reverse pattern was observed for the REG tempo, with the highest training volume (based on REP_sum1-5) related to the shortest duration of the exercise. This leads to the conclusion that the longest duration of exercise does not necessarily mean the highest training volume, which is contradictory to the standpoint of the training load analysis. The results of the study indicated that even a small ( (few seconds) modification in terms of tempo or cadence of particular movement phases can impact maximal REP, time under tension and, importantly, exercise volume in a set and in the whole training session. Movement tempo impacts training volume and, consequently, the level of post-exercise fatigue and adaptation patterns. The effect of a stronger training stimulus in case of the slow movement tempo can be observed even if the slower tempo leads to a decline in resistance training volume computed based on the number of repetitions as it was the case in our study. This is consistent with a study by Wilk et al. (2018), who documented higher post-exercise changes in testosterone, cortisol, CK and LA levels using the 6/0/2/0 tempo compared to the 2/0/2/0. Similarly, Antonutto and Prampero (1995) found significantly higher post-exercise blood lactate (BL) levels using a slow movement tempo. Hatfield et al. (2006) demonstrated that athletes who used slow movement tempos had, despite performing a smaller number of repetitions (and consequently lower exercise volume), greater post-exercise declines in generated muscle power compared to subjects who used a faster tempo. All these research reports demonstrated that movement tempo impacts not only exercise volume and post-exercise fatigue. Significant changes in TUT and REP in our study concern not only the entire experimental unit, but also individual values for each set (BP_s1, BP_s2, BP_s3, BP_s4, BP_s5). The study demonstrated a significantly higher REP in case of the REG tempo for BP_s1, BP_s2, BP_s3, BP_s4, BP_s5 and the opposite significantly higher TUT for individual sets in case of the MED and SLOW tempos. A higher number of repetitions (REP) in particular sets at REG tempo can be attributable to the use of elastic energy during the eccentric phase of contraction and its recovery during the concentric phase (Lindstedt et al., 2002). The results confirm previous findings published by Sakamoto and Sinclair (2006), who demonstrated that faster movement tempos helped perform more repetitions with a specific %RM (Table 4). Kraemer et al. (2002) and Westcott et al. (2001) demonstrated that slower movement tempo led to a decline in maximal muscle strength and, consequently, a decline in the number of repetitions, which is consistent with our results. Changes in TUT_set1–5 between SLOW, MED and REG tempos (Table 2) are observed in movement speed during both, the concentric and eccentric phases, but it seems that a particular slowdown of the movement in the eccentric phase can significantly impact total TUT(Wilk et al., 2018). The eccentric phase of the movement requires even 6 to 7 times lower oxygen demand compared to the concentric phase (Lastayo et al., 1999), which can have a direct impact on the results and significantly higher value of both TUT_set1–5 and TUT_sum1-5 at SLOW and MED tempos compared to REG tempo of movement (Table 2). Extending the duration of the eccentric phase of the movement is likely to be beneficial to skeletal muscle hypertrophy (Bird et al., 2005; Gumucio et al., 2015; Roig et al., 2009; Schoenfeld et al., 2017). Some authors provided evidence that lower speed during the eccentric phase led to increased muscle tension (Golas et al., 2018), and had a beneficial effect on muscle hypertrophy (Bird et al., 2005; Burd et al., 2011; Gehlert et al., 2015), whereas extended duration of muscle tension stimulated protein synthesis (Burd et al., 2010). The final value of TUT has a significant effect on the degree of mechanical and physiological post-exercise responses that have an impact on muscle adaptation. If time under tension increases, the volume of the work also increases, regardless of the number of performed repetitions.

The results of our study and previous scientific reports about the impact of movement tempo in resistance training indicate that TUT for a set and the entire training session can have a significant effect on the pattern and efficiency of adaptive processes. Tempo represents a component of resistance training, which should be controlled and taken into consideration during planning and following the resistance training programs. Slower movement speeds allow for extension of exercise duration, while reducing the number of repetitions. This observation undermines the legitimacy of the previously used method to determine resistance training volume based only on the number of performed repetitions. This allows to conclude that movement tempo and time under tension, rather than the number of repetitions are fundamental variables in evaluation of training volume and optimization of adaptive changes in the neuromuscular system. However, there is a need for the analysis of movement speed as another strength training variable. We suggest to evaluate the influence of this variable at various exercise intensities, using identical resistance training protocols.