Agonist-Antagonist Paired Set Resistance Training - A Brief Review

AGONIST–ANTAGONIST PAIRED SET RESISTANCE

TRAINING: A BRIEF REVIEW

DANIEL W. ROBBINS,1 WARREN B. YOUNG,1 DAVID G. BEHM,2 AND WARREN R. PAYNE1

1School of HumanMovement and Sport Sciences, University of Ballarat, Ballarat, Australia; and 2School of Human Kinetics andRecreation, Memorial University of Newfoundland, St. John’s, Canada

ABSTRACT

Robbins, DW, Young, WB, Behm, DG, and Payne, WR.

Agonist–antagonist paired set resistance training: A brief review.

J Strength Cond Res 24(10): 2873–2882, 2010—Agonist–

antagonist paired set (APS) training refers to the coupling of

agonist and antagonist exercises, performed in an alternating

manner with rest intervals between each set. The purpose of this

review is to identify the proposed benefits and possible

underlying mechanisms of APS training and to suggest how

APS training may be exploited. Furthermore, areas deserving of

further research attention will be presented. This review will also

suggest a common terminology (i.e., APS training) for describing

training modalities that alternate agonist and antagonist

exercises. Although somewhat equivocal, evidence exists

supporting the use of APS as a means of enhancing short-

term power measures. Evidence also exists suggesting APS

training is an efficacious and efficient means of developing

strength and power. Time-efficient methods of developing

strength and power would have benefits for athletes and the

general population. Athletes able to spend less time developing

strength and power would have more time to devote to other

aspects of performance or other unrelated tasks. The general

population may be more willing to adhere to less time-consuming

resistance training programs that offer similar results, as

compared to more time-consuming programs. This review

concludes that the practical applicability of APS training in

terms of acute performance enhancement is limited. However,

the use of APS training as an efficacious and time-effective

method for developing strength and power may hold some merit.

KEY WORDS super set, compound training, strength, complex

training, efficiency

INTRODUCTION

An agonist–antagonist paired set (APS) refers to thecoupling of exercises targeting muscle groups in anagonist-antagonist relationship, performed coin-cidentally in an alternating manner. For the

purposes of this review, APS training will involve combina-tions of heavy resistance or ballistic exercises, or a combina-tion of both, in an agonist-antagonist relationship. This reviewwill briefly discuss the proposed benefits of APS training, thesuggested underlying mechanisms, and possible implicationswith respect to APS training in terms of both acuteperformance enhancement and the development of strengthand power. Furthermore, the practical applicability of APStraining will be critically discussed to raise interest indetermining how best to exploit it. Directions for futureresearch will also be suggested. Finally, a common terminol-ogy (i.e., paired set) will be proposed.

TERMINOLOGY: WHY PAIRED SET?

Somewhat confusingly, under designations such as ‘‘complextraining,’’ ‘‘compound training,’’ and ‘‘supersets,’’ APS traininghas been prescribed by practitioners as a means of developingstrength and power. The term ‘‘superset’’ is arguably the mostcommon designation used by practitioners to describe APStraining. ‘‘Superset’’ has been used to describe varying protocols(1,28). Generally, the term would appear to be used to describegroups of exercises (i.e., usually 2) performed successivelytargeting different muscle groups but can be used to describeprotocols grouping exercises targeting the same muscle group.Because of the somewhat unclear definition of ‘‘superset,’’ andthe inappropriateness of other existing terms, a more definitiveterm is needed (Table 1). Hence, APS is introduced asa definition limited to agonist–antagonist pairs as compared tothe more broad interpretations of terms such as supersets,compound training, and others.

Empirical research has referred to APS-type training ascomplex (2,22,23), superset (14), and paired set training(21,24). To date, the most commonly used term in thescientific literature is complex training. A relatively large bodyof literature exists pertaining to complex training. However,complex training involves the coupling of biomechanicallysimilar exercises performed in an alternating manner and isbased upon the premise of performance enhancement via

BRIEF REVIEW

Address correspondence to Daniel Robbins, [email protected].

24(10)/2873–2882

Journal of Strength and Conditioning Research� 2010 National Strength and Conditioning Association

VOLUME 24 | NUMBER 10 | OCTOBER 2010 | 2873

Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

postactivation potentiation (19). Postactivation potentiationrefers to the phenomenon by which acute muscle force outputand rate of force development are enhanced as a result ofcontractile history. A number of varying complex trainingschemes have been investigated (9,20,31) and regardless ofmuscle group investigated, type of contraction, loadingscheme, or time line between exercises, the investigationsinto complex training and postactivation potentiation haveinvolved biomechanically similar exercises. Furthermore,investigations into complex training and post-activationpotentiation have focused solely on augmentation of poweroutput (PO) in the second half of the complex pair, or onchronic power development in the musculature targeted in thesecond half of the complex pair. More recently, 3 inves-tigations (2,22,23) coupling biomechanically dissimilar (i.e.,agonist–antagonist relationship) exercises have, perhapserroneously, referred to this scheme as a variation of complextraining. A training modality coupling biomechanicallydissimilar exercises, attempting to capitalize on mechanismsother than postactivation potentiation, with intentions otherthan solely enhancing acute or chronic PO, should perhapsnot be referred to as complex training (Figure 1). That is, APSshould perhaps not be associated with terms such as complextraining or postactivation potentiation. Although researchersand authors are correctly inclined to relate current research topast, to continue describing APS training as a form of complex

training is arguably erroneous. A quick search in a singledatabase (Medline) for articles with either complex training orpostactivation potentiation as a key word produced over250,000 hits. However, as previously mentioned, APS is notstrictly another form of complex training with a major purposeof eliciting postactivation potentiation effects. One of thepurposes of this review is to suggest a new, more appropriateterm and to create interest in researching this modality. To thebest of the knowledge of this group of authors, only 5 scientificinvestigations into APS training currently exist.

Although it may be suggested that another designation todescribe training modalities in which agonist and antagonistexercises are performed in an alternating manner will furtherconfuse, the authors argue that a common more tightlydefined terminology is necessary. Agonist–antagonist pairedset training would seem to be an accurately descriptive termto refer to this type of training. It is proposed that bothscientists and practitioners adopt this term.

PROPOSED BENEFITS OF PAIRED SETS

Agonist–antagonist paired set training modalities have beensuggested as a means to enhance PO in an acute setting (2) andas an efficacious and time-efficient means of developingstrength and power (21–24). The following is a brief discussionon each of these proposed advantages of APS training.

TABLE 1. Terminology used to describe agonist–antagonist paired set training and problems with that terminology.

Terminology Definition

Why terminology is notrepresentative of agonist–antagonist

paired set training

Agonist–antagonistpaired set training

Combinations of exercises in anagonist–antagonist relationship,performed in an alternating manner,primarily for the purpose of reducingtraining time.

Super set Describes groups of exercises(i.e., usually 2) performed successivelytargeting different muscle groups,but can be used to describe protocolsgrouping exercises targeting thesame muscle group.

Too broad. Does not exclusively describeagonist–antagonist exercise pairingsperformed in an alternating manner.

Compound training Describes pairs of exercisesperformed for the same musclegroup with minimal rest between sets.

Same muscle group. Does not describeagonist–antagonist exercise pairings.

Complex training Describes pairings of biomechanicallysimilar exercises with the intentof augmenting power output in thesecond exercise via postactivationpotentiation (i.e., excitation of themusculature to be used in theupcoming exercise by preloadingthat musculature.

Pairs biomechanically similar exercises.Intention is solely to augment poweroutput in second exercise.Underlying mechanism is postactivationpotentiation via preloading of musculatureto be used in the second exercise.

2874 Journal of Strength and Conditioning Researchthe TM

Paired Set Resistance Training


Acute Enhancement of Power Output

The execution of antagonist work before the performance ofa ballistic activity has been suggested to enhance PO of thatactivity (2). However, the findings of Baker and Newton (2)are contradicted by research observing no augmentation(23), or attenuation (14), in PO after antagonist loading. The3 studies investigating the potential for acute enhancementof PO in an APS setting implemented very different designswhich may explain the varying results.

In a population of trained male athletes (i.e., 24 rugby leagueplayers), Baker and Newton (2) observed an augmentation inPO in the bench press throw 3 minutes after a set of ballisticbench pulls, compared to PO in a set of bench press throwswith no intervention. It was suggested that antagonistpreloading may have altered (i.e., reduced the braking period)the triphasic firing pattern during the agonist power exercise.The researchers did not incorporate a mechanistic evaluation(e.g., electromyography) into the research to support thehypothesis that antagonist preloading altered the triphasicpattern during bench press throw. Furthermore, the prescribedwarm-up may have been inadequate, and therefore, anyperceived augmentation in performance was possibly becauseof a warm-up effect. That is, the pretest or baseline set of benchpress throws may have been performed in a state of

incomplete warm-up and thusacted to further prepare themusculature for upcoming work.Perhaps, rather than the aug-mentation in performance beinga result of an alteration in thetriphasic pattern resulting fromthe antagonistic work, as sug-gested by the investigators, theaugmentation was simply (orpartially) because of a warm-upeffect. It also appears that thetime lines were different forthe control and experimentalgroups. A longer rest intervalbetween sets of bench pressthrow was employed by theexperimental group as comparedto the control group and mayhave influenced the results.

Robbins et al. (23) observednonsignificant changes inpower measures over 3 APSs,in which bench press throwswere preceded by bench pullsin a population of trained,university-aged male athletes.Their research also reportednonsignificant differences inelectromygraphic (EMG) ac-tivity in the APS as compared

to a ‘‘traditional’’ protocol, in which all sets of the firstexercise (bench pull) were performed before all sets of thesecond exercise (bench press throw). A nonballistic in-tervention would not be expected to affect the triphasicpattern. The lack of augmentation in bench press throwperformance reported in the study by Robbins et al. (23) mayhave been because of the implementation of a nonballisticintervention (4 repetition maximum [4RM] bench pull)performed with low repetitions (with a tendency to decreasefrom sets 1 to 3), as compared to the intervention used byBaker and Newton (2) of 8 ballistic bench pulls. It is alsopossible, although perhaps unlikely, that performance wasenhanced to a similar extent in all 3 sets of APS bench pressthrow. This would not have been observed as a set of benchpress throw without intervention (e.g., before the first set ofbench pull) was not performed. However, the 3 sets of benchpress throw performed under the APS condition were notonly similar to one another but also similar to the 3 sets ofbench press throw performed under the ‘‘traditional’’condition. That is, if some augmentation occurred repeatedlyand to the same extent over 3 sets under the APS condition, itmust also have occurred under the ‘‘traditional’’ condition.It would seem unlikely that a similar level of augmentationoccurred in each set of bench press throw, under both

Figure 1. Differences between complex training and agonist–antagonist paired set training.


Journal of Strength and Conditioning Researchthe TM

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conditions, as a result of the cumulative effects of the varyingexercise performed before that set. Rather, it would seemmore likely that there was no augmentation in performance.

Maynard and Ebben (14) also failed to observe enhance-ment in performance in a population of trained, malecollegiate athletes completing maximal isokinetic kneeflexion and extension exercises. These researchers founda decrease in peak torque, rate to peak torque, and peakpower production in the agonist musculature when theantagonist muscle group was prefatigued. They measured theEMG activity of the agonist and antagonist musculatures andsuggested that perhaps the observed increase in EMGactivity of the antagonist (co-contraction) may have beenresponsible for the attenuation in performance measures. Itshould be noted that the investigators implemented a warm-up that included static stretching. It is generally accepted thatstatic stretching is not advised before performance (6,30).One could argue that, similar to the Baker and Newton (2)study, the warm-up was inadequate, and this may haveconfounded the results. It is unclear if there is a differentialresponse in the upper body as compared with the lowerbody. A greater level of coactivation in the antagonistmusculature may manifest itself as fatigue and affect thatmuscle group adversely when acting as an agonist.

Of the 3 studies to date (2,14,23) that have attempted toenhance PO after loading of the antagonist musculature, onlyBaker and Newton (2) reported augmentation. The study byBaker and Newton (2) was the only one in which a ballisticintervention was used in the upper body. If the intent ofa training protocol is to enhance acute PO via an antagonistintervention, it would seem likely that the nature of theintervention is important. It may be that in accordance withthe principle of specificity, upper body ballistic movementscan be augmented via an antagonistic ballistic movement.However, because of the limited and equivocal nature of theevidence, any conclusions would seem premature.

Strength and Power Development

It has been suggested that APS training is an efficacious meansof developing strength and power (22). Over the course of an8-week training period, a group of trained, male collegiateathletes performing APS training were reported to achievesimilar increases in 5 performance measures (1RM bench pulland bench press, throw height, peak velocity, and peakpower) as compared with the increases achieved by a similargroup which performed a ‘‘traditional’’ protocol in which allsets of pulling exercises were performed before pushingexercises in all training sessions (22). Under the APScondition, 1RM bench pull and bench press increases werestatistically significant, whereas the increases observed in themonitored power measures were not, leading the researchersto hypothesize that APS modalities may be better suited tostrength, as compared to power, development. Although theincreases in the monitored power measures were notstatistically significant under the APS condition, the increases

were similar to those observed under the ‘‘traditional’’condition. At this time, there is no reason to believe thatAPS training holds any advantages over traditional trainingschemes with respect to the development of power.

The obvious dearth in research makes any recommenda-tions difficult at this time. With respect to the onlylongitudinal study to date (22), it should be noted that thesample sizes were relatively small (i.e., 7 in the traditionalgroup and 8 in the APS group), and therefore, the power todetect statistically significance differences in the dependentmeasures under one, or both, of the conditions may havebeen limited. Furthermore, it is possible that the relativelylow prescribed training volume (i.e., 18–25 repetitions permuscle group, per session) and frequency (2 sessions perweek) did not provide a great enough stimulus over the8-week period to produce significant results in all measures,under both conditions, in the relatively highly trainedparticipants (i.e., minimum one- and generally several-yearsexperience). Perhaps longer (i.e., more repetitions) or morefrequent (i.e., more than 2 times per week) training sessionsover the course of the 8 weeks would result in statisticallysignificant gains being evident. However, it is important tonote that regardless of the relatively small sample sizes, lowvolume, and infrequency, statistically significant increases inboth strength measures were observed under the APScondition, making a strong case for the efficacy of APSstrength training. Although the lack of research makesrecommendations difficult, it does appear that APS trainingmay hold some merit as a means of developing strength.

Efficiency

Possibly the most intriguing role of APS training may be asa time-efficient method of developing strength and power. Ithas been hypothesized that in the event of similar, or evencompromised (i.e., lesser), outcomes under APS as comparedto other more time-consuming modalities (e.g., modalities nottargeting the antagonist musculature during rest intervalsbetween agonist work), APS training may be considereda time-efficient modality (21–24). Acute (output�time21,where output is the dependent measure, and time refers tothe time taken to achieve that output) and chronic(effect�time21, where effect is the dependent measure andtime refers to the time taken to achieve that effect) efficiencycalculations were performed in 4 studies (21–24) anddetermined APS training to have enhanced efficiency ascompared with ‘‘traditional’’ conditions in which agonistmusculature was targeted before antagonist musculature.Enhanced efficiency was observed with respect to all butone of the performance measures in one of the studies.Furthermore, effect size statistics performed in all 4 studiessupported the determination that APS training enjoyedenhanced efficiency. Specifically, large effect sizes wereobserved in 10 of the 13 performance measures.

Three of the 4 studies that performed efficiency calculationswere acute in nature. As previously discussed, Robbins et al. (30)



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investigated an APS coupling of bench pull and bench pressthrow performed over 3 sets and compared the outcomes toa ‘‘traditional’’ protocol and determined that although benchpull volume load (load 3 repetitions) decreased over the 3 sets,it did so to a similar extent under both conditions. Bench pressthrow performance was maintained over the 3 sets, and wassimilar under both conditions. Similar maintenance of throwheight, peak velocity, and peak power in the bench press throwexercise, volume load in the bench pull and similar EMG signalunder APS as compared with the ‘‘traditional’’ conditionindicate similar stress was imposed on the musculature inapproximately half the time, suggesting efficiency is enhancedunder APS training. Efficiency calculations and effect sizes fromthat study are presented in Table 2. In a subsequent study,Robbins et al. (24) investigated an APS coupling of 2 heavyresistance training exercises (bench pull and bench press)performed over 3 consecutive sets, and reported that althoughvolume load decreased from set 1 to set 2 and from set 2 to set3, there were no differences in volume load over the 3 sets, orover the sessions, in APS as compared to a ‘‘traditional’’condition. Because similar volume loads were achieved underthe less time-consuming APS condition, it was concluded thatAPS training was more efficient. Efficiency calculations andeffect sizes from that study are presented in Table 2. Althoughthere was a significant within-set EMG activity response in thebench press exercise, EMG activity was not different under the2 conditions, suggesting that the level of neuromuscular fatiguedid not differ under APS as compared to the ‘‘traditional’’condition. A subsequent investigation involving similar exer-cises (i.e., bench pull and bench press) compared an APS toa ‘‘traditional’’ condition but did so in a manner in which thetime to complete the sessions was constant (21). That is, thedenominator (time) in the efficiency calculation (out-put�time21) was similar under both conditions. Over 3 sets,bench pull and bench press volume load decreased significantlyfrom set 1 to set 2 and from set 2 to set 3 under both the APSand traditional conditions. Bench pull and bench press volumeload per set were significantly less under the traditional ascompared to APS condition over all sets, with the exception ofthe first set (bench pull set 1) in the sessions. Efficiencycalculations and effect sizes (large) from that study arepresented in Table 2 and indicate APS training, as comparedto the ‘‘traditional’’ condition, enjoyed enhanced efficiencyunder circumstances in which time lines were similar. Thesestudies only examined APS training performed over 3 sets. It ispossible that over longer training sessions, different outcomescould result in conclusions deeming APS inefficient (out-put�time21). However, with respect to the 2 acute studies withvarying time lines (i.e., APS completed in half the time requiredto complete the traditional protocol), volume load would haveto be compromised by more than 50% to deem APS traininginefficient. Such an outcome is perhaps unlikely. With respectto the study in which time lines were similar, there is no reasonto believe (i.e., lack of supporting evidence) a reversal in theobserved trends whereby volumes loads were significantly less

under the ‘‘traditional’’ as compared to the APS condition overall sets, would occur.

Under a previous section, ‘‘Strength and Power Develop-ment,’’ the results from a longitudinal study (22) were presented.Because the increases in performance measures were similarunder both conditions, the reduced time necessary to completethe APS sessions suggested that APS training is time efficientwith respect to the development of 1RM bench pull and benchpress, peak velocity and peak power. Efficiency calculationsand effect sizes from that study are presented in Table 2.Although limited, research into APS training that hascalculated efficiency is unequivocal in the determination thatAPS training is a time-efficient training modality. Agonist–antagonist paired set training can be recommended to thosedesiring to complete training sessions in less time, yet stillachieve similar results as traditional training.

PROPOSED MECHANISMS

The mechanisms underlying APS training are not wellinvestigated and are unclear. To more completely exploitAPS training, it is necessary to better understand the underlyingmechanisms. Mechanisms that have been suggested to in-fluence APS-type training include alteration in the triphasicfiring pattern (2) and phenomena associated with fatigue, suchas increased motor unit activation and increased activation ofsynergist and antagonist muscles (22–24). Although mecha-nisms associated with phenomena such as the stretchshortening cycle have been suggested to be implicated inagonist–antagonist movement pairs, the authors would arguethat the nature of APS training (i.e., the time betweenantagonist and agonist exercises and the independent characterof the 2 exercises) precludes the involvement of suchmechanisms. The time between agonist and antagonistcontractions necessary to elicit responses associated withstretch shortening cycle movements is less than 1 second (11).Rather, the mechanisms are likely linked to coactivation (2) andcontractile history (22–24). The contractile response of skeletalmuscle is partially determined by its contractile history (13).With respect to APS training, the contractile history of both theagonist and antagonist musculature must be considered.

Fatigue

Muscular fatigue can refer to a decrease in force-generatingcapacity (3,4). A number of mechanisms, including neuro-muscular and metabolic, are responsible for the decrease inforce-generating capacity. Metabolic fatigue at the cellularlevel can be attributed, at least in part, to the accumulation ofa number of metabolic byproducts, all or some of which maydisturb actomyosin cycling, Ca2+ sequestration and Na+/K+

exchange, thereby resulting in fatigue (8,16). Nonmetabolicfatigue can also result from intense activity and is characterizedby myofibrillar disorientation and cytoskeletal damage (8).

Agonist–antagonist paired set training is arguably morefatiguing than training modalities in which antagonist work isnot performed during the rest intervals between agonist




exercise sets. Although the rest interval between like exercisesis similar in APS- and ‘‘traditional’’-type protocols, thetraining density (work�time–1) is greater under APS, andextended bouts (i.e., more than 3 sets) of APS training arelikely more fatiguing. If, extended bouts of APS training areindeed more fatiguing than ‘‘traditional’’ training modalities,this may help to explain the chronic outcomes reported byRobbins et al. (22) and subsequent suggestions. Specifically,the suggestion that APS-type protocols may be better suitedto developing strength as compared to power, and that thereverse is true with respect to ‘‘traditional-type’’ protocols. Itwas hypothesized that the level of fatigue (i.e., greater fatigueunder APS because of less total rest time during trainingsessions) may have played a role in the outcomes (22).Greater levels of fatigue in subsequent power training setswould negatively impact movement velocity directly inhibit-ing a key factor in power development. It is possible thatelevated levels of fatigue, as a result of the increased trainingdensity inherent in APS training, may facilitate strengthdevelopment over extended training periods.

Fatigue may act as a stimulus, which leads to increases instrength (25). These researchers maintained a constant volumeload and varied rest intervals between contractions. Theydetermined that no rest between contractions led to greaterstrength gains than resting between contractions. It is possibleto infer from these findings that in the event volume load iscompromised (using similar rest intervals) under APS- ascompared to ‘‘traditional’’-type conditions, this may notadversely affect chronic gains in strength. In fact, it is possiblethat a reduced volume load as a result of fatigue may lead togreater gains in strength over a prolonged training period. Theprinciple of specificity suggests this factor (i.e., fatigue acting asa stimulus) may be less likely with respect to powerdevelopment. It is generally accepted that repeatedly achievinggreater POs in an acute setting over a prolonged period will leadto greater chronic adaptation, as compared with prolongedtraining at a lower level (29). That is, with respect to power,training at a higher level will result in adaptation at a higherlevel. Thus, the argument that fatigue may be beneficial tostrength and detrimental to power development may perhapsexplain the chronic outcomes reported by Robbins et al. (22).

The neuromuscular mechanisms by which fatiguingcontractions may lead to increases in strength are unclear.It has been suggested that training protocols which producefatigue result in greater motor unit activation than non-fatiguing protocols and that the level of motor unit activationdetermines the size of the training response (25). Alterna-tively, it has been suggested that fatigue might providea more appropriate setting in which to encourage activationof synergist and antagonist muscles and thereby increase thetraining response, or that some relationship might existbetween events related to fatigue and events that triggermuscle adaptation (25). Robbins et al. (22) reported nochanges in EMG activity pre to posttraining under either theAPS or ‘‘traditional’’ condition. It is therefore difficult to

postulate as to the appropriateness of the above suggestedmechanisms, by which fatigue may act as a stimulus forstrength, with respect to that study. Furthermore, Robbinset al. (22) did not monitor EMG signal during trainingsessions under either condition. It is therefore difficult tocomment on the level of fatigue resulting from APS ascompared with ‘‘traditional’’ training sessions in whichgreater than 3 sets are completed.

Coactivation

Coactivation refers to the concurrent activation of agonist andantagonist muscles (7,18). The antagonist musculature slowsthe movement initiated by the agonist musculature in sucha way as to allow for controlled movement. It has beensuggested that this concurrent activation may increase jointstability, aid in the prevention of injury and help to controllimb position (4,5,10,11,26). Thus, coactivation may work toimprove (e.g., through movement control) or inhibit (e.g.,through stiffening) performance.

Augmentation of subsequent agonist contractions might beattributed to a number of possible antagonist contraction-related mechanisms. These mechanisms might include (a)alterations to the triphasic pattern of ballistic contractions; (b)antagonist prefatigue decreasing resistance to the intendedmovement; and (c) enhanced activation of agonist becauseof reciprocal innervation. The following paragraphs willattempt to discuss each of these possible mechanisms inrelation to the current APS literature.

Alteration of the triphasic coactivation pattern (i.e., shorten-ing of the antagonist braking period) as a result of antagonistpreloading has been suggested as a possible mechanismresponsible for performance enhancement (2). Research intoAPS training as a means of enhancing acute performance hasfocused on movements involving high rates of powerdevelopment (2,23). These movements are commonly per-formed in an explosive or ballistic manner. Ballistic movementshave been associated with a triphasic pattern whereby there isan initial burst from the agonist musculature, followed bya burst from the antagonist musculature, and then a final burstfrom the agonist musculature (32). Arguably, a shortening ofthe antagonist braking burst would allow for a larger aggregateagonist firing period and could conceivably result in perfor-mance enhancement. Unfortunately, the researchers (2) whoput forward this theory did not incorporate the measurementof EMG activity data into the research design to support thispostulation. Therefore, any suggestion that PO may beaugmented via the alteration of the triphasic pattern as a resultof antagonist preloading is speculative at this time.

Prefatiguing the antagonist may decrease the resistance tothe intended movement resulting in enhanced performance ofagonist force output. It is possible that this, rather thanalteration of the triphasic pattern, may have been responsiblefor the enhancement in PO observed by Baker and Newton(2). One might wonder why a similar augmentation was notobserved by Robbins et al. (23) or Maynard and Ebben (14)



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as the antagonist musculature was prefatigued under theprotocols implemented by both groups of researchers.Perhaps the time line of any decrease in resistance resultingfrom prefatiguing of the antagonist was not captured becauseof an inappropriate rest interval between antagonist andagonist activity. Alternatively, the load or type of contractionmay have been inappropriate or at least was inappropriate inconjunction with the rest interval. It is also possible thatfactors such as training status, training age, chronological age,genetics (i.e., fiber-type composition), anthropometry, rela-tive strength, or absolute strength may have played a role.

Enhanced activation of the agonist musculature because ofreciprocal innervation (12,15,17) could result in augmentationof PO. Again, it is possible that this mechanism, rather thanalteration of the triphasic pattern, may have been responsiblefor the enhancement in PO reported by Baker and Newton(2). Perhaps if a submaximal intensity bout of antagonistcontractions was used by Robbins et al. (23) or Maynard andEbben (19), then a reciprocal innervation-induced activationof agonists would prevail over lingering fatigue affects.

Although the above-discussed mechanisms associated withcoactivation are generally accepted, evidence that thesephenomena can be manipulated through APS training toresult in performance enhancement does not exist. At thistime, any suggestions as to how coactivation and associatedmechanisms can be exploited via APS training are speculative.Research incorporating mechanistic approaches (e.g., EMG)is necessary to draw conclusions as to the role of coactivationin APS training.

EXPLOITATION OF PAIRED SETS

It has been hypothesized that APS training may be exploitedto achieve short-term enhancement of PO (2) and to achievechronic adaptation through training and thereby improveperformance (23). Factors deserving of consideration beforeattempting to capitalize on APS training in an acute orchronic setting will be presented in this section.

Acute Enhancement of Performance

Before any attempt to enhance acute athletic performancethrough the manipulation of antagonist contractile history viaAPS training, a number of variables need to be considered. Thetraining variables requiring consideration include type ofcontraction (i.e., isometric, concentric–eccentric, multijoint,etc.), intensity, volume (i.e., repetitions, sets, cadence, timeunder tension), rest interval(s) between possible multiple sets,rest interval within the APS couple, and responses of varyingmuscle groups. It is also possible that, as with many trainingmodalities, interindividual variability could further confoundany attempt to manipulate antagonist contractile history for thepurpose of enhancing performance. Because interindividualvariability exists, a number of categorical variables would alsoneed to be considered. These include training status, trainingage, chronological age, genetics (i.e., fiber-type composition),anthropometry, gender, relative strength, and absolute

strength. Before any conclusions can be made as to theefficacy of APS training in a warm-up protocol designed toenhance performance, further scientific research is necessary.

Strength and Power Development

Before designing APS training schemes aimed at developingstrength and power, many of the same variables (training andcategorical) considered with respect to acute performanceenhancement would need to be taken into account. Dependingon the combination of exercises, an APS protocol may beintended to develop strength or power or hypertrophy or anycombination of these (Figure 1). Training variables will tendto differ depending on the type (i.e., strength or power orhypertrophy or combination) of APS protocol and the goal(s)of that protocol.

PRACTICAL APPLICATIONS

Based on the above discussion, some recommendations can bemade regarding APS training with respect to acute performanceenhancement, chronic development of strength and power andtime efficiency. With respect to acute performance enhance-ment, 2 discussions are warranted. Firstly, a discussion as to thepractical applicability of APS training as a means to enhanceperformance precompetition, and secondly as a means by whichto train at a higher level and thereby adapt at a higher level.

As a means to enhance competitive performance in an acutesetting, APS may be of questionable benefit. The evidencesuggesting that antagonist preloading results in enhancementof power focused performance is limited and equivocal. Ifantagonist contractile history can be manipulated to result inacute enhanced performance, the question of feasibility israised. It would be a considerable task to determine trainingvariable parameters for countless different athletic profiles.Assuming training variables were determined in conjunctionwith categorical variables, a myriad of other implications couldFor example, possible practicality problems could include (a)the availability of equipment at the site of competition; (b)coordinating the potentiation and fatigue time lines within thecompetition time line; and (c) cumulative effects over thecourse of repeated trials (e.g., high jump).

Issues of transferability could also arise. Whereas a certainstimulus may act to enhance performance of a given activity, itmay not act to enhance performance of a different activity.Experiments would be necessary to determine the applica-bility of APS to various athletic activities. Furthermore, anysuggestion that antagonist preloading be employed beforecompetition with the intention of enhancing competitiveperformance would seem problematic without first de-termining a number of training variables appropriate to thatcompetitor or group of homogeneous competitors. Giventhe issues of practicality and equivocal nature of evidence todate, it would seem problematic to prescribe an APS-typewarm-up protocol before competition without further re-search confirming the effectiveness of such a modality.




Theoretically, if PO could be consistently augmented in anacute training setting, enhanced adaptation may occur. Asa means to develop power in a gym setting, issues withpracticality are less pronounced. Presumably, equipment isavailable and time lines can be controlled. However, even ifAPS training is feasible in a training setting, evidenceindicating it is advantageous in terms of acutely enhancingPO remains limited and equivocal. Any suggestion thatantagonist preloading results in power performance enhance-ment is premature.

Although limited, evidence exists suggesting APS training isan efficacious means of developing strength and power. Thesuggestion by Robbins et al. (22) that APS training may bebetter suited to strength, as compared to power adaptation, isinteresting and deserves further attention. Practitionersworking with athletes or the general population may be welladvised to consider APS training as a means of developingstrength. With respect to the development of power,practitioners may wish to be more cautious. Although Robbinset al. (22) reported similar increases in power measures underthe APS, as compared to the ‘‘traditional’’ condition, thepresented effect size statistics (Table 1) suggest that perhapsAPS training is not particularly well suited to poweradaptation. Although APS training would appear to be aneffective method of developing strength, recommendationswith respect to power adaptation may be ill-advised at thistime. Before the completion of further research, APS pairingsdesigned to develop strength (e.g., combinations of heavyexercises) may be more appropriate than pairings aimed atdeveloping power (e.g., incorporating ballistic exercises).

Perhaps the most confident recommendation can be madewith respect to APS training as an efficient training modality.The results of research to date (see Table 1) overwhelminglysuggest that APS training is a time-efficient method by which todevelop strength and power. In the absence of significantdifferences (acute or chronic) between traditional modalitiesand APS training, it could be argued that APS training elicitsresults similar to those of more traditional training methods butin a more time-efficient manner. Resistance training modalitiesthat aim to enhance musculoskeletal conditioning have beenassociated with improved health and a decrease in the risk ofchronic disease and disability (27). Athletes and trainers facea number of challenges in preparation for competition, and thegeneral population faces challenges with respect to themaintenance of health and wellness. Time is a constraint, andone such challenge, for athletes and the general population.Efficient resistance training schemes that do not compromiseefficacy, or increase efficiency, could be advantageous to notonly athletes but also the general population.

Attempts have been made to examine the practicalapplicability of APS with respect to enhancing acute athleticperformance, the efficacy of APS training as a means todevelop strength and power, and as a time-efficient trainingmodality. The results discussed in the literature regarding theenhancement of acute performance are equivocal, and the

task of determining possible parameters allowing forconsistent enhancement of acute performance is a dauntingone. With respect to chronic adaptation, some evidence doesexist to suggest that APS training is at least as beneficial, andmore time efficient, as other comparable training methodsdesigned to develop strength and power (22). At present, theexisting body of literature would seem to suggest that thepractical applicability of APS with respect to enhancing acuteathletic performance is limited. Agonist–antagonist paired settraining may be an efficacious and efficient method ofdeveloping strength and, to a lesser extent, power.

Practitioners and researchers need to be aware that therecommendations presented above follow from the limitedevidence available. To better understand possible benefits of APStraining and the associated underlying mechanisms, furtherresearch is necessary. There are many questions that remainunanswered, and researchers are encouraged to take a mecha-nistic research approach to further elucidate the potentialbenefits of APS training. Areas deserving of future researchinclude (a) acute power augmentation in the upper and lowerbody; (b) strength and power development in the upper andlower body; and (c) APS training aimed at hypertrophy.

Within these areas are a multitude of unanswered questionsrelated to the appropriate type of contraction, intensity, volume,rest intervals between possible multiple sets, rest interval withinthe APS couple, and the responses of varying muscle groups.Individual- or group-specific categorical variables also deserveattention. Researchers are further encouraged to consider timeefficiency regardless of the question and design. Some questionsthat remain unanswered include the following: (a) ‘‘Canantagonist ballistic movements enhance subsequent agonistPO in the upper body? Lower body?’’; (b) ‘‘Can APS be used todevelop strength in the upper body? Lower body?’’; (c) ‘‘CanAPS be used to develop power in the upper body? Lowerbody?’’; and (d) ‘‘Can APS be used to develop hypertrophy inthe upper body? Lower body?’’. With respect to these questions,the appropriate loading scheme and rest interval betweenagonist and antagonist work and between sets would need to bedetermined, creating a number of subquestions.

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Agonist-Antagonist Paired Set Resistance Training - A Brief Review

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