The effect of exercise induced hyperthermia on muscle fibre conduction velocity during sustained isometric contraction

Hunter, Angus, Albertus-Kajee, Yumna and St Clair Gibson, Alan (2011) The effect of exercise induced hyperthermia on muscle fibre conduction velocity during sustained isometric contraction. Journal of Electromyography and Kinesiology, 21 (5). pp. 834-840. ISSN 1050-6411

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Official URL: http://dx.doi.org/10.1016/j.jelekin.2011.06.002

Abstract

This study investigated the effect of dynamic exercise in a hot environment on muscle fibre conduction velocity (MFCV) of the knee extensors during a sustained isometric contraction. Seven trained male cyclists (mean [±SD], age, and were 35 ± 9.9 and 57.4 ± 6.6 ml kg−1 min−1) cycled for 50 min at 60% of peak power output in either: (1) 40 °C (HOT); or (2) 19 °C (NEUTRO); and (3) remained passive in 40 °C (PASS). Post-intervention a 100 s maximal sustained isometric contraction (SMC) of the knee extensors was performed. Rectal temperature increased (p < 0.01) for both HOT and NEUTRO with PASS unchanged and with HOT rising higher (p < 0.01) than NEUTRO (38.6 ± 0.4 vs. 37.6 ± 0.4 °C). Muscle temperature increased (p < 0.01) for all three conditions with HOT rising the highest (p < 0.01) (40.3 ± 0.5 vs. 38.3 ± 0.3 and 37.6 ± 1.3 °C for NEUTRO and PASS, respectively). Lactate showed higher accumulation (p < 0.01) for HOT than NEUTRO (6.9 ± 2.3 vs. 4.2 ± 2.1 mmol l−1). During SMC the torque, electromyography root mean squared (RMS) and MFCV all significantly (p < 0.01) declined. Only in HOT did MFCV decline significantly (p < 0.01) less than torque and RMS (9.9 ± 6.2% vs. 37.5 ± 17.8% and 37.6 ± 21.4%, respectively). In conclusion, during exercise induced hyperthermia, reduced motor unit recruitment as opposed to slower conducting properties of the muscle fibre appears to be responsible for the greater reduction in torque output.

Item Type: Article
Uncontrolled Keywords: Muscle fibre conduction velocity, EMG, RMS, hyperthermia, sustained isometric contraction
Subjects: C600 Sports Science
Department: Faculties > Health and Life Sciences > School of Life Sciences > Sport, Exercise and Rehabilitation
Depositing User: Ay Okpokam
Date Deposited: 11 Jan 2012 13:36
Last Modified: 10 Aug 2015 11:38
URI: http://nrl.northumbria.ac.uk/id/eprint/4491

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