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EFFECTS OF MAXIMAL VERSUS SUBMAXIMAL INTENSITY FATIGUE PROTOCOLS ON THE ELECTROMECHANICAL DELAY OF THE LEG EXTENSORS AND FLEXORS
EC Conchola, RM Thiele, BJ Thompson, D N Smith
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Abstract
Eric C.Conchola1,RyanM.Thiele1,Brennan J.Thompson2,& Doug B.Smith1; 1Oklahoma State University,Stillwater, OK; 2TexasTech University,Lubbock,TX Recent studieshaverevealed that neuromuscularfatigue leads toincreased electromechanical delay (EMD), and that differential recoverypatternsare exhibited betweenthe leg extensorand flexormuscle groups, whichmay adversely affectperformance and possibly increaselower extremity injury risks. However,it is unknownwhetherthese effects are influenced by theintensity levelofthefatigueprotocol. PURPOSE: Thepurposeofthis study was to investigate theeffectsofafatigue-inducing bout ofsubmaximal,andmaximal intermittent isometric contractions on the electromechanicaldelay ofthe legextensorsand flexors incollege-aged females.METHODS: Twenty young (age=21.23±1.41years) recreationally activefemalesparticipatedinafamiliarizationtrial followed byfour experimental fatigue sessions,separated byseven(±1) days. All sessionsbegan with participants performing maximal voluntary contractions(MVCs)followed by arandomly assigned fatigue-inducing protocol consisting of intermittent isometric contractions ofthe leg extensorsorflexorsusing a 0.6 duty cycle (6s contraction,4s relaxation)ateither 50% or 100%ofMVCuntil volitionalfatigue. MVCs were again performedat 0,7, 15,and 30 min post fatigue. RESULTS:Athree-wayrepeatedmeasures ANOVA (muscle[legextensorsvs.leg flexors]× intensity [submaximal vs.maximal]× time[Pre-vs.Post0vs.Post7vs.Post15vs.Post30]) wasusedto analyze the EMD data. There was nosignificant three-way interaction (P=0.134), nora two-way interaction formuscle × time (P=0.778),intensity × time (P=.072), ormuscle × intensity(P=0.842). However,there was a maineffect fortime (P=0.0001) where theEMD ofthe legextensorsand flexorswas greateratall postfatigue time periods comparedto Pre-,and Post0 was greatercomparedtoall other post time periods(P=0.001). Additionally,the EMD ofthe leg flexorswas greater(P=0.011) comparedtothe legextensors.CONCLUSIONS:Thesefindings showsimilar fatigue-inducedEMDeffectsand recoverypatternsbetweenthe legextensorsand flexorsat both maximal and submaximal intensities. ThesustainedincreasedEMD of the extensors and flexors during recovery may have important injury and performance implications inavarietyof populationsand settings; and theseeffects may be similarly incurred at bothsubmaximal and maximal contractionintensities