title: Torque and mechanomyogram correlations during muscle relaxation: effects of fatigue and time-course of recovery.
abstract: To assess the validity and reliability of the mechanomyogram (MMG) as a tool to investigate the fatigue-induced changes in the muscle during relaxation, the torque and MMG signals from the gastrocnemius medialis muscle of 23 participants were recorded during tetanic electrically-elicited contractions before and immediately after fatigue, as well as at min 2 and 7 of recovery. The peak torque (pT), contraction time (CT) and relaxation time (RT), and the acceleration of force development (d2RFD) and relaxation (d2RFR) were calculated. The slope and τ of force relaxation were also determined. MMG peak-to-peak was assessed during contraction (MMG p-p) and relaxation (R-MMG p-p). After fatigue, pT, d2RFD, d2RFR, slope, MMG p-p and R-MMG p-p decreased significantly, while CT, RT and τ increased (P < 0.05 for all comparisons), remaining altered throughout the entire recovery period. R-MMG p-p correlated with pT, MMG p-p, slope, τ and d2RFR both before and after fatigue. Reliability measurements always ranged from high to very high. In conclusion, MMG may represent a valid and reliable index to monitor the fatigue-induced changes in muscle mechanical behavior, and could be therefore considered an effective alternative to the force signal, also during relaxation.
authors.affiliation: Department of Biomedical Sciences for Health, University of Milan, Via G. Colombo 71, 20133 Milan, Italy; Centre of Sport Medicine, Don Gnocchi Foundation, Via Capecelatro 66, 20148 Milan, Italy.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Cè
authors.forename: Susanna
authors.initials: S
authors.lastname: Rampichini
authors.forename: Eloisa
authors.initials: E
authors.lastname: Limonta
authors.forename: Fabio
authors.initials: F
authors.lastname: Esposito
mesh_terms: D000054:Acceleration; D000328:Adult; D000704:Analysis of Variance; D004576:Electromyography; D006801:Humans; D008297:Male; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology; D015203:Reproducibility of Results; D019415:Torque
keywords: Force; MMG; Muscle relaxation; Off kinetics; Reliability; Torque