Resistance training is an effective method for developing muscular strength (4) and has been associated with improved health and a decrease in the risk of chronic disease and disability (22). One of the primary variables to be considered when designing resistance training programs is the volume of work prescribed. Volume of work may be described as volume load (VL) and be defined as the load multiplied by the number of repetitions performed with that load. It has been suggested that greater VL may lead to greater strength gains (9,12). Although prescribed, VL may vary depending on the goal of the program and philosophy of the designer, the ability to perform that prescribed VL in less time may be beneficial to both athletes and the general population. A number of training schemes have been suggested to achieve greater VL in a time-efficient manner (14-17,20). One such training scheme aimed at increasing VL per unit of time (VL/t), commonly prescribed by practitioners under designations such as “super set” or “compound set,” couples agonist and antagonist exercises in an alternating manner and may be referred to as “paired set (PS) training” (17). Among a variety of possible agonist-antagonist combinations is PS, which couples 2 heavy traditional weight training exercises (e.g., bench pull and bench press). Volume load/time may be viewed as a measure of efficiency, defined as work performed per unit of time, and may be increased by either decreasing time (the denominator) or increasing VL (the numerator).
Peer-reviewed research investigating PS-type protocols in an acute setting is limited (1,13,16,17), and only 2 (16,17) have examined the efficiency of PS-type protocols over repeated sets. The 2 multiset investigations compared a PS-type protocol to a “traditional” protocol. Bench pull and bench press VL, per set and session, were similar under both protocols. The PS-type protocols were completed in approximately half the time required to complete the “traditional” protocols. Specifically, the PS-type protocols were completed in 10 minutes as compared to the traditional set (TS)-type protocols, which required 20 minutes to complete. That is, the denominator in the efficiency equation (VL/t) was reduced under the PS protocol, thereby allowing the researchers to conclude that the PS-type protocols enjoyed greater efficiency as compared to the “traditional” protocols. However, it is unclear if similar results (i.e., enhanced efficiency) would be obtained were the testing sessions completed in similar time periods. Enhanced efficiency under such circumstances could only be achieved if VL were greater under PS, as compared to TS. Knowing that time is a crucial factor in the retention of the general population in fitness programs and training time for athletes, it is imperative to investigate the effect of similar 10-minute protocols.
Rest intervals between sets of resistance exercise are necessary to allow the exercised muscles to resynthesize intramuscular phosphocreatine and adenosine triphosphate and to remove metabolites detrimental to work production (3). It has been suggested that a 3- to 5-minute rest interval between resistance training sets is adequate to recover and perform a similar amount of work in successive sets (6-8). Under PS training, during the rest interval in which the initially exercised muscle group is recovering, the antagonist (to the muscle group initially exercised) musculature is targeted. Commonly, in a training session, sets of 1 exercise are completed before progressing to the next exercise. For the purposes of the current research, a TS protocol refers to sets of 1 exercise (e.g., bench pull) being completed before performing sets of another exercise (e.g., bench press) targeting the antagonist musculature. Assuming a similar time to complete training sessions, when comparing PS to TS, it is possible that under PS the initially targeted muscle group is better able to recover during its prolonged rest interval between like sets. This would also be the case for the musculature exercised in the second phase of the PS. Under PS, the exercises are performed in this alternating manner over consecutive sets. Assuming that more complete recovery is possible over multiple sets, VL may be increased per unit of time by concurrently training 2 muscle groups in such a manner. That is, the numerator in the “efficiency” equation (VL/t) is increased, thereby resulting in enhanced efficiency.
Commonly, athletes in a resistance training setting perform multiple sets of isotonic (i.e., load remains unchanged) exercises. To date, only 2 scientific studies have reported on the efficiency of PS in which agonist-antagonist pairings of isotonic exercises were investigated over consecutive sets, and they compared PS-type protocols to TS-type protocols where the TS-type protocols were designed to require approximately twice the time to complete. Research investigating PS in terms of efficiency in which the time to complete testing protocols is similar does not exist. To support the conclusion that PS training is efficient (16,17), research is necessary in which the time to complete protocols is held constant. It is possible that this method of training could be an efficient and efficacious method for developing strength. The purpose of this study was to investigate the efficacy (as measured by VL) and efficiency (VL/t) of agonist-antagonist PSs vs. TSs involving 2 heavy resistance exercises. It was hypothesized that PS training would provide both greater efficacy and efficiency as compared to TS.
Experimental Approach to the Problem
A within-design, randomized, counterbalanced comparison was used to investigate whether significant differences in VL (load × number of repetitions) efficacy and efficiency existed between PS and TS over 3 sets. Because of the familiarity of movement and their widespread use as a means to develop strength, bench pull and bench press were chosen as the pulling and pushing exercises, respectively. A 4 repetition maximum (4RM) load was prescribed for all sets in both protocols and was performed to failure, which was considered to have been reached when another repetition using proper technique could not be performed (23). The completed number of proper repetitions was recorded for each set and used to calculate VL for each set of both exercises. High-intensity loads (e.g., 4RM) performed over repeated trials have been recommended with respect to strength development (2,24). The TS protocol was designed to reflect the common practice of stressing 1 muscle group via multiple sets, before moving on to another muscle group. The PS protocol was designed to stress the same musculature as that stressed under the TS condition, but in an alternating manner. The total time required to complete the testing sessions was similar. The TS protocol involved performing 3 sets of bench pull followed by 3 sets of bench press, with a 2-minute rest interval between each set (Figure 1). The PS protocol performed the same exercises (bench pull and bench press), but the rest interval between like exercise sets was twice (4 minutes) that used in the TS protocol (2 minutes), and the rest interval between unlike exercise sets was 2 minutes. The second exercise set (bench press) was performed in such a manner that the midpoint of the execution of the second exercise set was 2 minutes after the beginning of the execution of the first exercise set (Figure 2).
Sixteen trained men with at least 1 year's training experience with pushing and pulling resistance exercises volunteered to participate in the study. Participants were generally collegiate athletes with several years of training experience, and testing occurred during the off season (the months of April and May). The participants' descriptive data are displayed in Table 1. The study was approved by the University Human Ethics Committee Review. Before the investigation, all subjects were briefed on the testing protocols, experimental risks, equipment, and the nature of the study before signing an informed consent document. All participants were asked to refrain from any upper-body training in the 48 hours before each training session.
Volume load was measured during all sets of both protocols by multiplying the load by the number of correct repetitions achieved. Participants underwent a familiarization session to determine their 4RM for the bench pull and bench press and were instructed on exercise technique. To determine 4RM, participants performed a set of 5-10 repetitions using 30-50% of expected maximum, followed 1 minute later by a set of 3-5 repetitions using 50-70% of expected maximum. After a 2-minute rest interval, 4RM attempts were made with approximately 2-minute rest intervals between attempts. If an attempt was successful using correct technique, further attempts were made using increasing increments of weight. The last successful attempt was recorded as the participant's 4RM in that lift. This procedure was adopted from Stone and O'Bryant (21) with one change: rather than 1-minute rest intervals between attempts, 2-minute rest intervals were used. The familiarization session was performed 1 week before the first testing session, which was performed 1 week before the second testing session. All testing was performed at the same time of the day, and a standardized warm-up (specific to the testing protocol) was performed in all 3 sessions. Before testing, participants performed progressive submaximal exercise. Specifically, participants performed 3 sets of lifts similar to the 2 lifts being tested, at 60, 80, and 90% of 4RM (calculated from the previously determined 4RM). A 4-minute rest interval was provided between like exercises. Before the TS testing session, the warm-up sets were executed in a successive manner-that is, 3 sets of the first exercise followed by 3 sets of the second exercise. Before the PS testing session, the warm-up sets were performed in an alternating manner.
All sets of both bench pull and bench press were performed to failure using previously determined 4RM loads. The bench pull tests were performed on an adjustable high bench (Apex B45 adjustable flat bench), positioned on Step1005 platforms. Participants were instructed to lie prone on the bench and grasp an Olympic bar placed on the floor, with a pronated grip. The bench was adjusted so that the participant's arms were straight in this position. A repetition was deemed to have been completed by moving the bar from the floor until it touched the bottom of the bench. Between repetitions the bar was motionless on the floor for 1-2 seconds. Hand placement and tempo were self-determined. Participants were instructed to keep their head, upper body, and legs flat to the bench. When performing the bench press, participants lay supine on a flat bench with feet flat on floor and head, shoulders and buttocks flat to the bench. A repetition was deemed to have been completed when the bar was moved from the chest to a position of full elbow extension. Between repetitions, the bar was momentarily held motionless on the chest. Hand placement and tempo were self-determined.
Before the commencement of the 3 testing sessions, a reliability study involving 10 of the subjects who later participated in the study determined the test-retest (separated by 1 week) intraclass correlation coefficients (ICCs) and percent total error (%TE).
Traditional Set Protocol
Before testing, participants performed the above-described standardized warm-up. Testing commenced after a 4-minute rest interval. Three sets of bench pull were followed by 3 sets of bench press, with a 2-minute rest interval between each set. All sets were performed to failure using a previously determined 4RM load. The load and number of correct repetitions completed were recorded for each set of both exercises. All sets of bench press were spotted by an experienced lifter to ensure volitional fatigue was achieved safely and with the confidence of the subject. The testing session took approximately 10 minutes to complete. Participants were given verbal encouragement during lifts. During the rest interval between sets, participants engaged in passive rest and were given verbal encouragement.
Paired Set Protocol
Before testing, participants performed a warm-up similar to that performed in the TS protocol, except that the submaximal exercises were performed in an alternating manner, rather than successively. Similar testing procedures to those used in the TS protocol were implemented. However, the 3 sets of bench pull were performed in an alternating manner with the 3 sets of bench press. Also, although the rest interval between like sets was 4 minutes, the rest intervals between work performed were less. At the midpoint of the rest interval between like sets, the other exercise (i.e., antagonistic) was executed. The rest interval between work performed was approximately 2 minutes. Therefore, the testing session was completed in approximately 10 minutes. Participants were given verbal encouragement during lifts. During the rest interval between sets, participants engaged in passive rest and were given verbal encouragement.
The set and session totals of VL for bench pull and bench press in both testing protocols were calculated. These data were analyzed using a 2-way analysis of variance (2 × 3), 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 (1-3). Analysis of the data to determine if any significant differences existed between the 2 testing protocols was performed to investigate the influence of PS on the maintenance of VL. Efficiency (VL/t) calculations were also made. Paired t-tests were used to compare the percentage changes in bench pull to those in bench press. The level of statistical significance was set at p ≤ 0.05 for all tests. All statistical tests were completed using Statistica version 6 (Tulsa, OK, USA). Effect size calculations were performed on measures of VL (5).
The reliability study determined ICCs and %TE for set and session VL over 3 sets for bench pull ranged between 0.75 (4.2%) and 0.83 (9.5%), and the same for bench press ranged between 0.82 (6.4%) and 0.96 (13.7%). Paired sample t-tests revealed no significant (p ≤ 0.001) differences between the 2 testing occasions.
Independent analysis of testing protocols found that both bench pull and bench press VL decreased significantly from set 1 to set 2 and from set 2 to set 3 under the PS and TS conditions (p < 0.05). The percent changes, from set to set, in bench pull and bench press are shown in Table 2. Bench pull and bench press VL per set were significantly less under TS as compared to PS over all sets, with the exception of the first set (bench pull set 1). Furthermore, session totals for bench pull and bench press VL were significantly less under TS as compared to PS. Volume load data and effect sizes for bench pull and bench press are shown in Table 3. Paired set training was determined to be more efficient. Efficiency calculations are shown in Table 4. Under the PS condition, the percent decreases in bench press were significantly greater than those observed in bench pull from set 1 to sets 2 and 3. Under the TS condition, the percent decreases in bench press were significantly greater than those observed in bench pull from sets 1 and 2 to set 3.
The most important findings of this study were (a) significantly greater bench pull and bench press VL observed under the PS as compared to the TS protocol, suggesting greater efficiency under the PS protocol, and (b) the apparent cumulative effects of fatigue, generated by antagonist work, on agonist performance. Although PS-type protocols have been previously reported to enjoy enhanced efficiency (16,17), this was achieved by manipulating the time to complete testing sessions, rather than observing significant increases in VL using similar timelines, as is the case in the current research. The significantly lower VL observed in the first set of bench press under TS as compared to PS would seem to suggest that antagonist work may have a cumulative fatiguing effect on subsequent agonist performance. To the best of the researchers' knowledge, similar findings have not been previously reported. Previous multiset investigations into PS-type training (16,17) did not report differences in performance measures of the first set of the second exercise.
Regardless of level of performance, volume of work prescribed is a primary variable to be considered in the design of strength and conditioning programs. The ability to perform a prescribed VL in reduced time will be beneficial to athletes and the general population. It has been suggested that PS-type training protocols are time efficient, thereby allowing for greater training density (16,17). In the present study, bench pull and bench press VL were significantly less per set, and for the session, under TS as compared to PS. Efficiency calculations (see Table 4) determined PS training to have greater efficiency as compared to TS training. These findings would seem to support the hypothesis that with respect to PS training, efficiency is enhanced in both the bench pull and bench press exercises.
The observed set-to-set significant reductions in VL in bench pull and bench press under TS would seem to indicate that a 2-minute rest interval is inadequate with respect to maintaining VL. This is perhaps not surprising because investigations into TS-type training protocols have reported an inability to maintain VL using a similar load (i.e., 4RM) and a longer rest interval (i.e., 4 minutes) in both the bench pull and bench press (16,17). A 4-minute rest interval between similar exercise sets under the PS protocol was also inadequate in terms of VL maintenance. This is also in agreement with previously reported findings (16,17). It would appear that under either training design implemented in the current research, the prescribed rest interval did not allow for a level of physiological recovery (e.g., resynthesis of intramuscular phosphocreatine and adenosine triphosphate and removal of detrimental metabolites) adequate to return the body to a state in which a similar amount of work could be performed in subsequent sets. It has been suggested that the rest interval necessary to maintain VL is dependent on the magnitude of the load and, specifically, that submaximal (i.e., <90% of 1RM) loads performed to failure require longer rest intervals as compared to maximal (i.e., 1RM) loads (24). As the present study was constrained by a 4RM load, it is possible that a load of greater intensity (i.e., 1-3RM) may allow for VL maintenance over repeated sets using either of the prescribed rest intervals in the current study.
Although bench pull and bench press VL decreased significantly from set to set under both conditions, the decreases observed under TS were significantly greater than those observed under PS. The significantly lower VL observed under the TS condition resulted from the inability to complete as many repetitions under the TS, as compared to the PS, condition (Figures 3 and 4). A significantly lower VL was observed in all but the first set (i.e., bench pull set 1) of the sessions under TS, as compared to PS. It was not expected that differences would be observed between the first sets of the sessions because they were performed in a similar, nonfatigued state under both conditions. The data suggest that the prolonged rest interval between like sets enjoyed under PS, as compared to TS, allowed for greater physiological or mental recovery, or both, and resulted in the attainment of greater VL. Given a similar timeline, manipulation of the order in which the exercises were performed under PS allowed for the targeted musculature to enjoy a longer rest interval. Results would seem to suggest that the effects on VL maintenance of alternating agonist and antagonist work is somewhat less detrimental than are the effects of performing multiple sets of one exercise before performing multiple sets of another.
It was expected that greater VL would be observed in subsequent sets (i.e., second and third sets) of both exercises under PS, as compared to TS. However, a significantly greater VL was also observed under PS, as compared to TS, in the first set of bench press. The data suggest that performing 3 sets of bench pull before performing a set of bench press (with 2-minute rest intervals between each set) is more fatiguing than performing 1 set of bench pull 2 minutes before performing a set of bench press. That is, there would appear to be some cumulative effects of general (i.e., not localized to the musculature predominantly involved in the movement) fatigue associated with antagonist work that is reflected in subsequent agonist work. It would seem likely that this is somewhat dependent on the length of the rest interval between sets and, specifically, that longer rest intervals would mitigate this observed effect. In previous research, under a TS-type protocol using a 4-minute rest interval between sets, cumulative effects of fatigue (VL and electromyography [EMG]) were not observed in the antagonist musculature after 3 sets of agonist work (17). Specifically, VL and EMG activity were similar in an initial set of bench press after 3 sets of bench pull with a 4-minute rest interval between sets as compared to bench press VL and EMG activity after 1 set of bench pull performed 2-minutes before. It is possible that TS-type protocols implementing a 4-minute rest interval, as compared to TS-type protocols implementing a 2-minute rest interval, allow for more complete recovery of the antagonistic musculature. Although cumulative “general” fatigue is commonly experienced by participants during resistance training sessions, this phenomenon has not been well documented in the literature and deserves further attention.
Although bench pull and bench press VL decreased from set to set under both conditions, it is interesting to note that the percentage decreases were greater in the bench press, as compared to the bench pull, under both the PS and TS protocols. In comparing percentage changes in VL between sets of bench press to bench pull, 4 of the 6 comparisons (see Table 2) revealed that the decreases in bench press were significantly greater than those observed in bench pull. Specifically, under the PS condition, the percent decreases in bench press were significantly greater than those observed in bench pull from set 1 to sets 2 and 3 and under the TS condition, the percent decreases in bench press were significantly greater than those observed in bench pull from sets 1 and 2 to set 3. This can perhaps be explained by the fiber-type composition of the musculature predominantly involved in the bench pull, as compared to the bench press, exercise. The percentage of type 1 (fatigue-resistant) fibers in the musculature primarily involved in the bench pull is greater than that in the musculature primarily involved in the bench press exercise (10,19). It has been suggested that the musculature involved in pulling movements may be more fatigue resistant than that involved in pushing movements (16,17). It is possible that the musculature involved in the bench pull is more fatigue resistant than the musculature involved in the bench press and may explain why the observed decreases were larger in the bench press than in the bench pull under both conditions.
Because of the nature of PS training, coactivation (the concurrent activation of agonist and antagonist muscles) should be considered. Muscle activity is partially dependent on contractile history (11), and it is therefore possible, although perhaps unlikely, that the mechanisms associated with coactivation played a role in the attainment of greater VL observed under the PS protocol in the current research. It has been suggested that preloading may alter the braking phase of the triphasic pattern of the previously loaded musculature when acting as an antagonist during subsequent power exercise (1)-specifically, that the braking period of the antagonist is shortened, thereby allowing for a longer total agonist burst. However, the triphasic pattern is associated with ballistic movement and is unlikely to have been a factor in protocols that used 4RM loads. It is possible that fatigue associated with coactivation influenced results. That is, activation of the musculature when acting in an antagonistic manner resulted in fatigue, which negatively influenced performance of that musculature when acting as an agonist.
Resistance training sessions aimed at exercising multiple muscle groups commonly involve >2 exercises and 6 sets. Furthermore, the maintenance of a greater acute VL under PS, as compared to TS, does not necessarily yield equivalent, or effective, chronic development of strength. Outcomes in acute efficiency (VL/t) do not necessarily translate into similar outcomes in chronic adaptation. That PS training is an efficient training method as compared to TS training does not necessarily mean that PS training is efficient with respect to chronic adaptation. Acute efficiency is negatively affected by fatigue. However, it has been suggested that fatigue may, in fact, act as a stimulus for strength development (18). That is, the variable responsible for reducing acute efficiency may act to enhance chronic development. Longitudinal research investigating the effects of PS training is necessary to determine the efficacy and efficiency of PS training.
Under designations such as “super sets,” “compound sets,” “contrast sets,” and others, PS-type training has been prescribed by practitioners for years. Incorporation of PS-type modalities into training programs is commonly performed as a time-saving measure. However, scientific research investigating PS-type protocols in terms of time efficiency is limited. The current data indicate that heavy resistance (4RM) PS training allows a greater loading to be imposed on the musculature than that achieved with TS training. Given similar timelines, it would appear that performing agonist and antagonist work in an alternating manner, as compared to performing all sets of agonist work before completing sets of antagonistic exercise, allows for greater recovery and subsequently greater loading. More complete physiological recovery will allow higher volumes of work to be performed. Practitioners working with time-constrained clients (athletes or the general population) may be well advised to incorporate PS-type training into prescribed programs.
Data from the current study indicate that neither a 2-minute rest interval nor a 4-minute rest interval (with antagonist work done during this rest interval) is adequate with respect to maintaining VL over repeated sets. Programs incorporating 4RM loads with the intent of maintaining VL over multiple sets may choose to use longer rest intervals. Comment on rest interval lengths adequate to maintain VL using loads similar to those used in the current study is beyond the scope of this research. Data from the current study also indicate that there may be cumulative effects of general fatigue. That is, practitioners should be aware that antagonist work may influence subsequent agonist work. If certain exercises in a training session are considered to have greater importance, practitioners may wish to prescribe such exercises before performing antagonist work. Furthermore, when tracking performance measures (e.g., VL) over a training cycle, practitioners should be cognizant of the order in which the exercises have been performed in each session. Also, it would appear that the musculature involved in pulling movements may be more fatigue resistant than the musculature involving in pushing movements. If this is the case, practitioners may wish to account for this when prescribing pushing and pulling exercise.
Predictions regarding the chronic effects of PS training would be speculative at this time. However, it is possible that PS-type protocols are an effective and efficient method for developing strength. For athletes, less time spent developing strength should translate into more time to develop other aspects of performance and theoretically result in performance enhancement. For the general population, possibilities of results in less time should attract greater numbers of people to resistance training. Resistance training has been associated with improved health and a decrease in the risk of chronic disease and disability (22), and therefore, increases in participation will likely have a positive effect on the health of the general population. Before prescribing PS training to certain groups within the general population, practitioners may be well advised to examine other possible physiologic responses (e.g., blood pressure) to such training. Given the possibility that PS training may be beneficial to both athletes and the general population, longitudinal studies investigating the chronic effects of PS training are warranted.
The authors would also like to thank the University of Victoria (Canada) for the allowance of laboratory space and equipment. The authors have no conflicts of interest that are directly relevant to the contents of this manuscript.
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