Volume Load and Neuromuscular Fatigue During an Acute Bout of Agonist-Antagonist Paired-Set vs. Traditional-Set Training

Abstract

Paz, GA, Robbins, DW, de Oliveira, CG, Bottaro, M, and Miranda, H. Volume load and neuromuscular fatigue during an acute bout of agonist-antagonist paired-set vs. traditional-set training. J Strength Cond Res 31(10): 2777–2784, 2017—The purpose of this study was to investigate the acute effects of performing paired-set (PS) vs. traditional-set (TS) training over 3 consecutive sets, on volume load and electromyographic fatigue parameters of the latissimus dorsi, biceps brachii, pectoralis major, and triceps brachii muscles. Fifteen trained men performed 2 testing protocols (TS and PS) using 10 repetition maximum loads. The TS protocol consisted of 3 sets of bench press (BP) followed by 3 sets of wide-grip seated row (SR). The PS consisted of 3 sets of BP and 3 sets of SR performed in an alternating manner. Volume load was calculated as load × repetitions. The electromyographic signal, time (C_RMS) and frequency (Cf5) domain, parameters were recorded during SR. Under the PS protocol, sets of SR were performed immediately after the sets of BP. A 2-minute rest interval between the completion of the set of SR and the subsequent set of BP was implemented (e.g., between PSs). Under the TS protocol, 2-minute rest intervals were implemented between all sets. BP and SR volume loads decreased significantly from set 1 to set 2 and from set 2 to set 3 under both conditions. Volume load was greater for all sets of both exercises under PS as compared with TS. Muscle fatigue indices were greater under PS as compared with TS. In general, these results indicate that as compared with TS, PS produced a greater training volume in less time and may induce greater fatigue and thereby provide an enhanced training stimulus.

Introduction

Resistance training is an efficacious method of developing muscular strength and power (¹). One of the primary variables to be considered when designing a resistance training program is the training volume or volume load (VL), often calculated as number of repetitions × external load (^22,25). Volume load reflects the stress placed on the activated muscle group. Volume load is associated with neural, hypertrophic, metabolic, and hormonal responses to resistance training (²⁰). It has been suggested that increases in this variable may lead to greater gains in strength (¹¹).

Several resistance training programs have been developed, which increase VL in a time-efficient manner (^7,21). One such method is known as agonist-antagonist paired-set (PS) training and refers to the use of agonist and antagonist exercises performed in an alternating manner (²⁴). Decreases in training time are realized by reducing the rest interval between antagonist muscle groups (²²). That is, time efficiency associated with PS training is premised on the concept that antagonist exercise performed between agonist exercise sets may be done so with relatively short rest intervals between agonist and antagonist bouts without compromising outcomes (^20,23,24). Paired-set training differs from traditional-set (TS) training in which all sets of the same exercise are performed before the execution of all sets of the next exercise. Previous studies have shown that as compared with TS, PS reduces the resistance training session duration (^20,22) and provides a higher level of muscle fatigue (⁷) and can improve muscle strength performance (^6,15).

At present, the neuromuscular responses to PS are unclear. Using an integrated electromyographic (EMG) signal, Maynard and Ebben (¹⁷) observed an increase in hamstring coactivation under PS (5 knee flexions followed by 5 knee extensions) as compared with TS (5 knee extensions). This increase in coactivation was associated with significant decreases in peak torque and peak power. In contrast, over a series of studies, Robbins et al. (^20,21,23,24) observed no significant differences in the number of power-related indices, VL and EMG during PS, as compared with TS. Using reduced rest intervals, Maia et al. (¹⁵) observed significant increases in knee extensor performance after antagonist preloading. Under similar protocols (e.g., shortened rest intervals after antagonist preload), the authors also found significant increases in normalized root mean square (RMS) of the vastus medialis and rectus femoris muscles. Although a number of mechanisms (e.g., facilitatory stimulation of Golgi tendon organs and muscle spindles) have been suggested to explain the above-described responses to antagonist preloading, both the neuromuscular responses and underlying mechanisms remain unclear.

When planning and prescribing resistance training programs, a greater understanding of predicted outcomes and the mechanisms underlying those outcomes is beneficial. To date, studies examining the neuromuscular impact of PS have focused on EMG measures, such as the RMS and mean or median frequency (^17,23,24). Because of the subjective selection of boundary frequency and/or high- and low-frequency bands (³), these techniques have limited ability to evaluate muscle fatigue during dynamic tasks (^2,10). Electromyographic spectral indices have been reported to demonstrate greater sensitivity during dynamic contractions (¹³). To the best of our knowledge, no study has used EMG spectral indices to assess muscle fatigue during PS. The purpose of this study was to use well-suited EMG measures (e.g., the Dimitrov spectral index of muscle fatigue and amplitude) to assess muscle fatigue during a dynamic PS protocol and to provide support for the hypothesis that as compared with a TS protocol antagonist preloading via PS may increase acute strength performance.

Methods

Experimental Approach to the Problem

A randomized crossover design study was carried out in 4 test sessions on nonconsecutive days (Figures 1 and 2). Because of the familiarity of movement and widespread use as a means to develop strength, bench press (BP) and wide-grip seated row (SR) were chosen as the pulling and pushing exercises, respectively. In the week before the first session, 10 repetition maximum (RM) loads were determined for the BP and SR exercises during test and retest sessions. Moderate-intensity loads (e.g., 10RM) performed over repeated trials have been recommended with respect to strength and hypertrophy development (¹). To assess muscle fatigue and VL during a dynamic PS vs. TS protocol, the following protocols were applied: (a) TS participants performed 3 sets to failure of BP followed by 3 sets to failure of SR. Two-minute rest intervals were implemented between sets and exercises; (b) In PS, the antagonist preloading was assessed performing a set of BP immediately followed by one set of SR. The time required for participants to change exercises was approximately 10 seconds. A 2-minute rest interval was adopted before the next PS (BP and SR). The recovery period between the experimental protocols was between 48 and 72 hours. The number of repetitions completed for all sets under both protocols was recorded. Electromyographic signal of the latissimus dorsi (LD), biceps brachii (BB), pectoralis major (PM), and triceps brachii (TB) muscles was recorded during the SR exercise in each protocol. The EMG indices of fatigue (Cf5 and C_RMS) were computed to compare the neuromuscular fatigue response between TS and PS protocols. Fatigue-induced changes in nonstationary EMG signals can provide an indication of general motor unit activation and signal frequency, respectively (¹⁰).

Figure 1.: Schematic representation of traditional-set protocol. 10RM = 10 repetition maximum; BP = bench press; SR = seated row.

Figure 2.: Schematic representation of paired-set protocol. 10RM = 10 repetition maximum; BP = bench press; SR = seated row.

Subjects

Fifteen recreationally trained men participated in the study. Participant descriptive data (mean ± SD) are as follows: age 22.4 ± 1.1 years (range between 18 and 30), height 175 ± 5.5 cm, weight 76.6 ± 7.0 kg, and percent body fat 12.3 ± 2.1%. All participants signed written informed consent forms. All participants had previous resistance training experience (3.5 ± 1.2 years), averaging four 60-minute sessions per week. Participants generally implemented 1- to 2-minute rest intervals between sets and exercises. All participants were active in approximately 2–4 hours of recreational or competitive sports training or were active in competition 1–5 times per week. This study was conducted during the hypertrophic phase of the periodization program of all subjects. The participants included in this research did not consume dietary supplements in the form of carbohydrates, proteins, or amino acids. No participants used anabolic steroids either before or while participating in this research. All test participants were informed on how to remain properly hydrated to avoid the influence of dehydration on strength performance.

The current study was approved by the Institutional Human Experimental Committee at the Federal University of Rio de Janeiro. All participants completed the Physical Activity Readiness Questionnaire and signed an informed consent before participating in this study according to the Declaration of Helsinki. All participants were instructed to avoid any upper-body exercise in the 48 hours before each session.

Ten Repetition Maximum Testing

At each of the first 2 sessions, strength was assessed using a 10RM test for BP and SR exercises (Figure 3) on Life Fitness equipment (Life Fitness, Rosemont, IL, USA). The 10RM load was chosen to assess muscular strength. The 10RM test was performed at a constant pace (2 seconds for both concentric and eccentric contractions) and was controlled by a metronome (Metronome Plus 2.0; M&M Systeme, Braugrasse, Germany) (¹²). If the participant did not attain 10 repetitions in the first attempt, the weight was adjusted by 4–10 kg and a minimum of 5 minutes of rest was given before the next attempt. Ten-minute rest intervals were adopted between exercises to test the 10RM loads. BP and SR exercises were alternated during test and retest. Only 3 trials were permitted per testing session. The test and retest sessions were conducted 48 hours apart.

Figure 3.: Bench press (A) and wide-grip seated row (B) being performed.

To reduce the margin of error in testing, the following strategies were adopted (¹⁸): (a) in order that all subjects were aware of the entire data collection routine, standardized instructions were provided before the test; (b) subjects were instructed on the technical execution of the exercises; (c) the researcher carefully monitored the position adopted during the exercises; (d) consistent verbal encouragement was given to motivate subjects for maximal repetition performance; and (e) the additional loads used in the study were previously measured with a precision scale.

Procedures

Participants came to the laboratory on 4 different occasions, with a minimum rest interval of 72 hours between visits. All tests were completed on Monday, Wednesday, and Friday at the same time of the day (8–10 am) between July and August. Subjects reported to the laboratory in the morning and then consumed a standardized breakfast (approximately 320–350 calories) with a protein to fat to carbohydrate ratio of 20:35:45 (protein, fat, carbohydrate as percentage).

Experimental Protocols

During the third session, participants were assigned to the TS or PS group in a randomized fashion. The fourth session consisted of performing whichever protocol was not performed in the third session. Before each protocol, participants performed a warm-up set of 15 BP repetitions using 50% of 10RM loads (^12,27). A 2-minute rest interval was implemented after the warm-up set. Ten repetition maximum loads were used for each protocol. Under TS, participants performed 3 sets to failure of BP followed by 3 sets to failure of SR. Two-minute rest intervals were implemented between sets and exercises. Under PS, participants performed one set of BP immediately followed by one set of SR. The time required for participants to change exercises (from BP to SR) was approximately 10 seconds. A 2-minute rest interval was adopted before the next PS (BP and SR). Participants performed 3 PSs. The rest interval between like sets of BP and SR was approximately 170 seconds (the time spent to perform each exercise plus the time to move to the next exercise plus the 2-minute rest interval). After the standardized warm-up, the average session duration was 16 ± 3.5 minutes under TS and 8.5 ± 2.3 minutes under PS. The number of repetitions completed for all sets under both protocols were recorded. Under each protocol, during the SR exercise, EMG activity of LD, BB, PM, and TB muscles was recorded.

Surface Electromyography

The EMG signal was captured through passive bipolar surface electrodes (Kendal Medi Trace 200; Tyco Healthcare, Pointe-Claire, Canada), acquired by a dedicated data acquisition system (EMG System of Brazil, Sao Jose dos Campos, SP, Brazil). The signals were amplified by 1,000 Hz (common-mode rejection ratio > 100 dB) and sampled at 1,000 Hz after being band-pass filtered (10–500 Hz). The simple differential active electrodes (input impedance of 10¹⁰ Ohm, passband prior sampling of 0.1–500 Hz) had polyethylene foam with hypoallergenic medical adhesive, solid stick gel, bipolar contact of Ag/AgCl, and a between-pole distance of 20 mm. Precautions were taken to avoid the dynamic EMG limitations. Skin surface was shaved, slightly abraded, and cleaned with alcohol swabs before placing the EMG surface electrodes. To avoid the possibility of cross talk, electrodes were placed on the corresponding muscle belly aligned with the fiber direction, according to SENIAM standards (²⁶). Placement and location of the electrodes were made in accordance with the surface EMG for the noninvasive assessment of muscles after the recommendations by Cram and Kasman (⁹). The PM electrode was placed at the midpoint between the acromion and the xiphoid processes. The LD electrode was placed lateral to the inferior angle of the scapula. The BB electrode was placed on the line between the medial acromion and the cubit fossa. The TB electrode was placed halfway between the acromion process and the olecranon process at 2 finger widths below the medial line. The reference electrode was placed on the clavicle bone. The impedance between electrode pairs was less than 5 kΩ using a 25-Hz signal through the electrodes. All these procedures were performed by the same investigator. Placement of the electrodes was identified on the first day of testing, and an indelible pen mark was made on the skin to ensure that a similar electrode position was used on the subsequent day.

After the recommendations for muscle testing function proposed by Cram and Kasman (⁹), at each visit, all subjects performed a maximum voluntary isometric contraction (MVIC) for PM, LD, BB, and TB in a randomized design. The MVIC was performed for 2 sets of 5 seconds each, with a rest interval of 2 minutes (⁷). The EMG analysis was conducted with a MatLab subroutine specially designed for this study. The EMG signal was normalized using the MVIC. In the normalization procedure, the MVIC repetition with the highest RMS value across the 3 middle seconds of the signal was used as a reference. A 10-minute rest interval was adopted before beginning the experimental protocols.

Data Processing

Commonly, the RMS together with the mean and/or median frequency of the EMG power spectrum has been used to evaluate muscle fatigue (²⁸). To overcome the problem of low sensitivity of those spectral parameters during dynamic contractions, a new highly sensitive spectral index called FI_nsm5 was adopted to quantify the spectral changes of muscle EMG during fatigue. This method is in accordance with the procedure of Dimitrov et al. (¹⁰). The conventional fast Fourier transformation was applied to calculate the spectrum density. The spectral moments were then used to extract the features of the spectral density of the EMG signal using equation 1:where M_k is the spectral moment of order K, PS(f) the EMG power spectrum, as a function of frequency f of the signal bandwidth, fmin to fmax (20–450 Hz). The fatigue index was calculated as the ratio between spectral moments of orders 1 and 5 for each exercise repetition (equation 2). The fatigue index changes (increases representing greater fatigue) were based on a comparison between the first and subsequent repetitions within each set. The first set was always referred to as 100% and subsequent sets were based on the equation:

The FI_nsm5 was calculated for each repetition and muscle. Those values, together with the time duration of each contraction, were used to perform a linear regression, from which the coefficient (Cf5) was used for further comparisons (⁷). The RMS was calculated for each entire contraction (concentric and eccentric) during the SR exercise, with the beginning and ending of each contraction selected visually from the EMG signal. A linear regression was performed of the series formed by all values obtained and the corresponding time duration of each value. The coefficient of this regression (C_RMS, uV·min⁻¹), together with Cf5, was taken as the parameter to be compared across the experimental protocols. All digital processing procedures were performed by using the custom-written software MatLab5.02c (Mathworks, Natick, MA, USA).

Statistical Analyses

All data are presented as mean ± SD. The Shapiro-Wilk normality test and a homoscedasticity test (Barlett criterion) were used to test the normal distribution of the data. All variables presented a normal distribution and homoscedasticity. The dependent variables were EMG indices of fatigue (Cf5 and C_RMS) and volume load (repetition × load). Test-retest reliability of 10RM loads and EMG spectral parameters was conducted using the intraclass correlation coefficient {ICC = (MSb − MSw)/(MSb + [k − 1] MSw)}, where MSb = mean square between, MSw = mean square within, and k = average group size. These data were analyzed using a 2-way analysis of variance (ANOVA) (protocols × sets) with repeated measures and paired t-tests to determine whether there were significant main effects or interactions for the type of training (TS and PS) and the sets (1, 2, and 3). Electromyographic data were analyzed using a 2-way ANOVA (2 × 3) with repeated measures to determine whether there were significant main effects or interactions for the type of training (TS and PS) and sets (1, 2 and 3). Post hoc tests using the Bonferroni correction were employed when necessary. The VL (load × repetitions) for each set was calculated for BP and SR. Paired T-tests were used to compare the session VL (load × repetitions for entire session) between protocols for each exercise. The level of statistical significance was set at p ≤ 0.05 for all tests. The effect size was also computed after the recommendations of Rhea (¹⁹) for recreationally trained individuals (Trivial: <0.35; Small: 0.35–0.80; Moderate: 0.80–1.50; Large: >1.5). The statistical analyses were performed with SPSS version 20.0 (SPSS, Inc., Chicago, IL, USA).

Results

The reliability study determined that ICCs and percentage difference for average and total VL over 3 sets for BP and SR ranged between 0.92 (5.9%) and 0.95 (9.4%), respectively. Paired sample t-tests revealed no significant (p < 0.001) differences between the 2 testing occasions. The test-retest ICC of the EMG measures for the 4 monitored muscles ranged between 0.91 and 0.92. Mean and SD of the 10RM loads was 83 ± 3.4 kg for BP and 68.5 ± 3.4 kg for SR exercises.

Significant reductions in VL were found for BP and SR exercises between sets 1 and 2 and sets 2 and 3 under both protocols. Volume load for SR was significantly lower under the TS, as compared with PS, over the 3 sets. Volume load was significantly lower for BP under TS, as compared with PS, for sets 2 and 3. Session VL was greater under PS, as compared with TS, for both BP and SR. Session VL was higher for PS (1,328 ± 27.5 kg) as compared with TS (1,188.4 ± 115 kg, p = 0.002) for BP exercise. This was also true for the SR exercises TS (960.5 ± 100.1 kg) and PS (1,249.4 ± 135.5 kg, p = 0.0001). The percent change in VL from sets 1 to 3 was significantly less under PS, as compared with TS, for BP exercise. There was no significant difference in the percent change between protocols for SR exercise. Volume load data, percent changes, and effect sizes are shown in Table 1. Higher repetition performance was noted for SR exercise under PS for sets 1 (p = 0.0001), 2 (p = 0.001), and 3 (p = 0.0001) when compared with the TS protocol (Figure 4). Similar results were noted for BP exercise for sets 2 (p = 0.001) and 3 (p = 0.0001).

Table 1.: Volume load (kilograms) completed in each set for agonist-antagonist paired-set (PS) and traditional-set (TS) protocols (mean and SD) and effect size data. The ∆% represents the decrease from the first to the third set. Mean (SD) (N = 15).

Figure 4.: Repetition performance of each participant performed in bench press and wide-grip seated row exercises between paired-set and traditional protocols. §Significant difference as compared with traditional-set protocol.

Significant increases in LD and BB amplitude coefficients (C_RMS) were noted from set 1 to 2 and 2 to 3 for both protocols. As compared with TS, increases in LD muscle activity (C_RMS) were observed under PS during sets 1, 2, and 3. Augmentation of BB muscle activity was only observed for set 3 under PS, as compared with TS. Reduced PM muscle activity was observed in sets 1, 2, and 3 under PS, as compared with TS. Reduced muscle activity was also observed for the TB muscle in sets 1 and 2 under PS, as compared with TS. No differences were noted between sets and protocols for the TB muscle (Figure 5).

Figure 5.: Coefficient of root mean square linear regression (values in percentages) for agonist and antagonist muscles during the performance of wide-grip seated row between paired-set and traditional protocols. Curves represent the average between sets. *Significant difference for set 1. §Significant difference as compared with traditional-set protocol.

Significant increases in the fatigue index (C_RMS and Cf5) were noted from sets 1 to 2 and sets 2 to 3 during SR exercise for all muscle groups evaluated under both PS and TS. The LD muscles showed a higher fatigue index (e.g., Cf5) under PS, as compared with TS, during sets 1, 2, and 3 (Figure 6). The EMG fatigue index was also higher for the BB muscle for sets 2 and 3 under PS, as compared with TS. This result was also observed for the PM muscle during sets 1, 2, and 3. The TB muscle showed a higher fatigue index during sets 2 and 3 under PS, as compared with TS.

Figure 6.: Fatigue index (values in percentages) for agonist and antagonist muscles during the performance of wide-grip seated row between paired-set and traditional protocols. Curves represent the average between sets. *Significant difference for set 1. §Significant difference as compared with traditional-set protocol.

Discussion

Previous research has suggested that PS training is a time-efficient method to maintain VL in an acute setting (^20,21,23,24). The results of the present study indicate that antagonist preloading via PS (with minimal allowable rest) may allow for increased VL in a time-efficient manner. Volume load was greater for both BP and SR under PS, as compared with TS. This, in conjunction with the elevated fatigue indices (EMG) observed for agonist and antagonist muscle groups during SR under the PS protocol, suggests that PS, as compared with TS, may provide significant increases in acute muscle strength performance.

Of the 6 comparisons of VL (3 sets each of BP and SR), only the first set of BP was not significantly different. Given that this set of exercise was preceded by nothing other than the standardized warm-up, this is not surprising. Each of the other 5 comparisons yielded significantly greater VL under PS as compared with TS. These data are in disagreement with some previous studies, which suggested that PS yields similar VL in a time-efficient manner (^7,8,20). One possible explanation is that the time between like sets of exercise was greater under PS as compared with TS in the present study, as compared with those implemented in previous studies. Robbins et al. (²⁰) implemented 2-minute rest intervals between like sets. In the present study, the rest interval after the BP or SR set was approximately 120 seconds. Thus, under the PS protocol, the effective rest between like sets was approximately 10 seconds to move from BP to SR plus the time to complete the set of SR or BP exercises of approximately 40 seconds (e.g., 10 repetitions at a cadence of 2-second concentric and 2-second eccentric contractions). That is, under PS, the rest interval between like sets was 2 minutes and 50 seconds. This longer rest interval of approximately 50 seconds (42% greater) between like sets under PS, as compared with TS, may have allowed for greater recovery and greater VL.

Although the present study is in disagreement with some previous research (^7,17,20), it does seem to support that of Maia et al. (¹⁵). Those researchers observed greater repetition performance (with 10RM loads) when performing a set of knee extension immediately after a set to failure of lying leg curl (e.g., antagonist preloading), when compared with knee extension without antagonist preloading. The authors observed this potentiated effect using 30-second and 1-minute rest intervals, but not when implementing longer rest intervals (e.g., 3- and 5-minute rest intervals). This suggests that the rest interval between PS exercises may play an important role. This is supported by previous studies, which adopted longer rest intervals and did not find differences in agonist muscle strength performance (^{7,8,20,21,23,24}). It is possible that antagonist preloading using minimal rest intervals may potentiate subsequent agonist exercise.

A variety of mechanisms (e.g., neural adjustment of golgi tendon organs, increased elastic energy storage, alteration of triphasic neural pathways) have been proposed to explain antagonist preload–induced performance (^4–7). It is also possible that the changes in Cf5 observed for BB and LD under both protocols may be partially related to an increase in the duration of the motor unit action potential waveform and subsequent decrease in muscle fiber conduction velocities (¹⁰). According to Woods et al. (²⁹), motor neuron firing rates are inhibited by some reflex originating from the muscle, generated in response to either mechanical or metabolic changes that accompany fatigue. Martin et al. (¹⁶) observed that when comparing elbow extensor and flexor maximal sustained contractions, motor neurons are not uniformly affected by inputs from group III and IV afferents, when preceded by antagonist preloading. Those researchers also found that if inhibitory influences from these afferents are more pronounced on extensor motor neurons, then, all other things being equal, these muscles will require greater cortical output to generate a given force during fatigue (¹⁴).

In the present study, the muscle fatigue index was able to detect performance variations between protocols. Significant increases in the fatigue index (Cf5 and C_RMS) were noted over the 3 sets of SR exercise for the LD, BB, and PM muscles under both protocols. Increases in Cf5 were observed for the TB muscle under both protocols. Paired-set presented higher levels of muscle fatigue, as compared with TS, for the LD, BB, PM, and TB muscles. This lower fatigue index in the TS protocol may be because of the order of the antagonist preloading, which may lead to a higher degree of muscle recovery between like sets. The increased EMG amplitude observed during PS (C_RMS) might be primarily attributed to additional motor unit recruitment and/or increased spatial (²) or temporal motor unit synchronization (³), presumably to compensate for muscle fiber fatigue (¹³). An increase in the fatigue index (Cf5) has previously been associated with changes in spectral moment of order 1 across repetitions (¹⁰), emphasizing the changes in low and ultralow frequencies in the EMG spectrum (³). Spectral moment of order 5 conferred greater magnitudes of change at high frequencies (¹³). Such outcomes have previously been attributed to the increased duration of the intracellular action potentials and decreased action potential propagation (²⁸).

This study has limitations that warrant mentioning. Because of the factors such as muscle speed, fiber, and length, the interpretation of the EMG signal during dynamic tasks may increase the nonstationary characteristics of the EMG signal. Additionally, the current study only examined 2 upper-body resistance exercises, whereas resistance training sessions typically include various exercises performed over multiple sets.

A secondary finding of the present study was the observed decreases in VL for both BP and SR across sets under both protocols. These data suggest that a 2-minute rest interval was inadequate to maintain VL. This finding is consistent with previous PS research in which VL was not maintained when using rest intervals of 1–4 minutes between like exercise sets (^18,23,24).

Practical Applications

The results of the present study suggest that upper-body antagonist preloading via PS may increase muscle strength performance in acute manner and may be a practical alternative to TS with respect to increasing VL in a time-efficient manner. The elevated fatigue indices observed during PS could be useful in developing muscle strength and hypertrophy for both antagonist and agonist muscle groups. Paired-set may be useful for coaches and athletes who are seeking to enhance acute muscle performance and increase VL and/or reduce the training session duration.