title: Human capacity for explosive force production: neural and contractile determinants.
abstract: This study assessed the integrative neural and contractile determinants of human knee extension explosive force production. Forty untrained participants performed voluntary and involuntary (supramaximally evoked twitches and octets - eight pulses at 300 Hz that elicit the maximum possible rate of force development) explosive isometric contractions of the knee extensors. Explosive force (F0-150 ms) and sequential rate of force development (RFD, 50-ms epochs) were measured. Surface electromyography (EMG) amplitude was recorded (superficial quadriceps and hamstrings, 50-ms epochs) and normalized (quadriceps to Mmax, hamstrings to EMGmax). Maximum voluntary force (MVF) was also assessed. Multiple linear regressions assessed the significant neural and contractile determinants of absolute and relative (%MVF) explosive force and sequential RFD. Explosive force production exhibited substantial interindividual variability, particularly during the early phase of contraction [F50, 13-fold (absolute); 7.5-fold (relative)]. Multiple regression explained 59-93% (absolute) and 35-60% (relative) of the variance in explosive force production. The primary determinants of explosive force changed during the contraction (F0-50, quadriceps EMG and Twitch F; RFD50-100, Octet RFD0-50; F100-150, MVF). In conclusion, explosive force production was largely explained by predictor neural and contractile variables, but the specific determinants changed during the phase of contraction.
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: J P
authors.initials: JP
authors.lastname: Folland
authors.forename: M W
authors.initials: MW
authors.lastname: Buckthorpe
authors.forename: R
authors.initials: R
authors.lastname: Hannah
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007717:Knee / Q000294:innervation / Q000502:physiology*; D016014:Linear Models; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D052097:Quadriceps Muscle / Q000294:innervation / Q000502:physiology
keywords: contractile properties; explosive strength; neural drive