The Acute Time Course of Concurrent Activation Potentiation

Transcription

1 Mrquette University Exercise Science Fculty Reserch nd Publictions Exercise Science, Deprtment of The Acute Time Course of Concurrent Activtion Potentition Luke Grceu Mrquette University, Erich Petushek Northern Michign University McKenzie Futh Mrquette University Willim Ebben Mrquette University, Published version. Published s prt of the proceedings of the conference, Proceedings of the XXVIII Congress of the Interntionl Society of Biomechnics in Sports, Permlink Interntionl Society of Biomechnics in Sports. Used with permission.

2 THE ACUTE TIME COURSE OF CONCURRENT ACTIVATION POTENTIATION Luke R. Grceu 1, Erich J. Petushek 2, McKenzie L. Futh 1, nd Willim P. Ebben 1, 3 Deprtment of Physicl Therpy, Progrm in Exercise Science, Strength nd 1 Conditioning Reserch Lbortory Mrquette University, Milwukee, WI, USA Deprtment of Helth, Physicl Eduction, nd Recretion, Northern Michign University 2 Mrquette, MI, USA Deprtment of Helth, Exercise Science & Sport Mngement, University of Wisconsin- 3 Prkside, Kenosh, WI, USA This study evluted the cute time course of the ergogenic effect of concurrent ctivtion potentition (CAP). Forty-two men nd women, including CAP non-responders nd responders, performed 5 second isometric knee extension on dynmometer with the use of remote voluntry contrctions (RVC). Men torque ws ssessed in seven 500 millisecond (ms) time periods. A two-wy repeted mesures ANOVA reveled significnt min effects for time period (p 0.001), but no significnt interction between time period nd CAP non-responders nd responders (p > 0.05). The ergogenic effects of CAP re ccrued during the first 1000ms. Concurrent ctivtion potentition responders produce greter initil force thn the CAP non-responders, without concomitnt ccelertion in force decy throughout the time course. KEYWORDS: strength, power, ltency, Biodex, motor overflow INTRODUCTION: Sustining enhnced muscle performnce is the primry gol of strength nd conditioning progrms. Ergogenic strtegies hve been sought nd the phenomenon of concurrent ctivtion potentition (CAP) hs shown promise. Concurrent ctivtion potentition is believed to increse prime mover muscle ctivtion during the simultneous contrctions of muscles remote from the prime mover vi motor overflow (Ebben, 2006). These simultneous contrctions re defined s remote voluntry contrctions (RVC). Previous reserch ssessing the effects of CAP hve demonstrted increses in torque during isometric testing (Ebben et l., 2008b) nd force development during the countermovement jump (Ebben et l., 2008). To dte, the time course of the ergogenic CAP effect hs yet to be exmined. Computerized dynmometry is commonly used nd relible tool to mesure musculr performnce of the knee (Surkk et l., 2005) producing vribles of power, work, rte of torque development (RTD), nd pek torque. Reserch exmining the effects of RVC on pek torque hve demonstrted n 8.9% increse in isokinetic knee flexion for men, compred to condition without the use of RVC (Ebben et l., 2010b). Knee extensors hve lso been exmined isokineticlly nd hve shown pek torque increses of 8.4 (Stumbo et l., 2001) nd 10.6% (Ebben et l., 2010b) for men nd 4.2% (Ebben et l., 2010b) for women during conditions when RVC were used. Additionlly, men nd pek torque increses of 14.6 nd 14.8%, respectively, were demonstrted during n isometric knee extension with the simultneous use of RVC (Ebben et l., 2008b). These studies confirm tht torque is greter in the presence of RVC but do not explin the durtion of this dvntge. Reserch evluting the effect of RVC on RTD nd rte of force development (RFD) provide some evidence tht the ergogenic effect of CAP my occur erly during dynmic movements. Vrious durtions of force development hve been used to ssess CAP s effect: RTD of the first 300ms (Ebben et l., 2010b), RFD of the first 100ms (Ebben et l., 2010), RFD of the concentric phse (Ebben et l., 2008), RFD to pek force (Ebben et l., 2010), nd time to pek force during the concentric phse (Ebben et l., 2008), ll resulting in RVC ided performnce increses of 14.6, 32.2, 19.5, 8.2, nd 20.2%, respectively. Therefore, it cn be hypothesized tht CAP s ergogenic effect is ccrued quickly.

3 Thus, the purpose of this study ws to ssess RVC on men torque during 500ms time periods of isometric knee extension in CAP non-responders nd responders, in order to investigte the time course of the ergogenic effect of CAP. METHODS: Forty-two subjects prticipted in this study who were previously clssified s CAP non-responders (N=11; men ± SD, ge 20.9 ± 1.9 yr; body mss 69.7 ± 9.8 kg) nd responders (N=31; men ± SD, ge 21.3 ± 1.6 yr; body mss 75.7 ± 12.0 kg). Inclusion criteri consisted of t lest 2 months of biweekly prticiption in lower body resistnce trining with exercises tht included knee extension. Subjects were excluded if they presented ny history of knee pthology tht resulted in functionl limittion of the right leg. All prticipnts competed in NCAA Division I thletics, club, or intrmurl sports, nd hd plyed high school sports. Prticipnts refrined from resistnce trining for t lest 48 hours prior to testing. All were informed of the risks ssocited with the study nd provided informed written consent. The study ws pproved by the institution s internl review bord nd designed in ccordnce with the ethicl stndrds of the Helsinki Declrtion. Subjects wrmed up nd performed 15 seconds of lower body dynmic stretching for ech mjor muscle group. Subjects were then positioned nd secured in dynmometer (System 4, Biodex Inc., Shirley, NY, USA) ccording to mnufcturer specifictions. Strps cross the chest, wist, right thigh, nd right nkle reduced extrneous movement during the exercise. The right knee joint ws positioned goniometriclly t 90 degrees nd clibrted with the system softwre nd the mss of the limb ws mesured. Knee joint ngle ws then djusted until the softwre indicted the knee ws t 60 degrees of flexion. Test specific wrm up sets of two 5 second isometric knee extension exercises t 75 nd 90% of their self-perceived mximum bility were then performed. During the exercise, subjects simultneously used RVC including mximl jw clenching on dentl vinyl mouth gurd (Crmer Products Inc., Grdner, KS, USA), mximl bilterl hnd griping using hnd dynmometers (model 78010, Lfyette Industries, Lfyette, IN, USA), nd the performnce of the Vlslv mneuver. Five minutes of rest were provided between wrm up nd test sets. Testing consisted of one mximl isometric right knee extension for 5 seconds on the dynmometer with the simultneous use of the forementioned RVC. Subjects were instructed to perform mximlly. Isometric torque curves for ech subject were nlyzed using mnufcturer s softwre. Men torque ws clculted for ech of seven 500ms time periods: 0-500, , , , , , nd , totling 3.5 seconds. The onset of the 0-500ms time period ws identified by the first positive torque vlue in the torque curve. All dt were nlyzed using SPSS A two-wy repeted mesures ANOVA ws used to evlute men torque, expressed s percentge of body weight, for the time period nd the interction between the time period for CAP non-responders nd responders. Bonferroni djusted pirwise comprisons were used to ssess the specific differences between time periods nd CAP non-responders nd responders. Sttisticl power (d) nd effect size (η p ²) re reported nd ll dt re expressed s mens ± SD. The priori lph level ws set t p RESULTS: The nlysis of men torque, expressed s percentge of body weight, reveled significnt min effects for time course (p 0.001, η p ² = 0.79, d = 1.00) but no significnt interction between the time course for non-responders nd responders (p = 0.844). Results of the pirwise comprison re demonstrted in Tble 1 nd Tble 2 in order to provide descriptive dt for CAP non-responders nd responders, respectively.

4 Tble 1. Men isometric right knee extension torque s percentge of body weight (men ± SD) during 500 millisecond time periods for CAP non-responders (N=11) ms ± ms ± ms ± ms ± ms = millisecond Significntly different (p 0.001) thn ll other time periods ms ± ms ± ms ± Tble 2. Men isometric right knee extension torque s percentge of body weight (men ± SD) during 500 millisecond time periods for CAP responders (N=31) ms ± ms ± ms ± ms ± ms = millisecond Significntly different (p 0.001) thn ll other time periods ms ± ms ± ms ± DISCUSSION: This is the first study to investigte the time course of the ergogenic dvntge of CAP during isometric knee extension. Non-responders nd responders of CAP demonstrted similr torque mintennce during the time course even though the CAP responders men torque ws greter, s shown in previous studies (Ebben et l., 2008; Ebben et l., 2008b; Ebben et l., 2010; Ebben et l., 2010b). Prctitioners cn use this knowledge to prescribe RVC without concern of higher thn usul cute performnce decy. This study is the first to demonstrte tht the use of RVC do not present performnce decresing cost to motor resources. Evlution of the CAP responder s men torque throughout the time course demonstrtes the first two 500ms time periods re significntly different thn the rest. In the first time period, 0-500ms, the CAP responders demonstrted 10.1% greter men torque/ body weight percentge thn the CAP non-responders. Collectively, these dt potentilly explin the performnce enhncements in RTD (Ebben et l., 2010b), RFD (Ebben et l., 2008; Ebben et l., 2010b), nd time to pek force (Ebben et l., 2008; Ebben et l., 2010b). The performnce vribles ssessed in the present, s well s the forementioned studies, ll evluted force production within the first 500ms or less. The CAP responder s non-significntly greter men torque vlue within the first 500ms of the exercise, compred to the CAP non-responders, is consistent with results from previous reserch (Ebben et l., 2008; Ebben et l., 2008b; Ebben et l., 2010; Ebben et l., 2010b), nd together, these dt suggest the ergogenic effect of CAP my only occur during the first 1000ms in strength nd power tsks. The present study demonstrtes no significnt difference in force mintennce between CAP non-responders nd responders, with both showing nerly identicl percent differences in men torque vlues throughout the durtion of the time course. Men torque incresed 45.8 nd 48.9% from the 0-500ms to the ms time period for CAP non-responders nd responders, respectively. CAP non-responders nd responders gin demonstrted similr men torque increses of 6.6 nd 8.8%, respectively, from the ms to the ms time period. The comprtively similr liner performnce enhncement of the CAP nonresponders nd responders is consistent throughout the durtion of the exercise, suggesting the knee extensor s performnce is not eventully hindered during the use of RVC. Consistent with the present study, previous literture ssessing the effect of RVC on isokinetic knee flexor nd

5 extensor strength hs demonstrted increses in the kinetic knee performnce of CAP responders but not CAP non-responders (Ebben et l., 2010b). Therefore concluding, the use of RVC my improve, but do not eventully impede musculr performnce. CONCLUSION: Results of the present study demonstrte CAP s ergogenic effect occurs within the first 1000ms. Concurrent ctivtion potentition non-responders nd responders present no differences in force mintennce, thus the use of RVC do not continully impede musculr performnce regrdless of the individul s response to CAP. Thus, regrdless of n individul s response to CAP, the use of RVC will not dversely ffect performnce. REFERENCES: Ebben, W.P. (2006). A brief review of concurrent ctivtion potentition: theoreticl nd prcticl constructs. Journl of Strength nd Conditioning Reserch, 20, Ebben, W.P., Flngn, E.P., & Jensen, R.L. (2008). Jw clenching results in concurrent ctivtion potentition during the countermovement jump. Journl of Strength nd Conditioning Reserch, 22, Ebben, W.P., Leigh, D.H., & Geiser, C.F. (2008b). The effect of remote voluntry contrctions on knee extensor torque. Medicine nd Science of Sports nd Exercise, 40, Ebben, W.P. nd Petushek, E.J. (2010). Kinetic nlysis of concurrent ctivtion potentition during bck squts nd jump squts. Journl of Strength nd Conditioning Reserch, In press. Ebben, W.P., Petushek, E.J., Futh, M.L., & Grceu, L.R. (2010b). Electromyogrphicl nlysis of concurrent ctivtion potentition. Medicine nd Science of Sports nd Exercise, (epub hed of print). Surkk, J., Virtnen, A., Aunol, S., Mentk, K., & Pekkrinen, H. (2005). Relibility of knee muscle strength nd ftigue mesurements. Biology of Sport, 22, Stumbo, T.A., Merrim, S., Nies, K., Smith, A., Spurgeon, D., & Weir, J. (2001). The effect of hndgrip stbiliztion on isokinetic torque t the knee. Journl of Strength nd Conditioning Reserch, 15, Acknowledgement Trvel to present this study ws funded by Green By Pckers Foundtion Grnt.