Strength training counteracts motor performance losses during bed rest

• Published in: Journal of applied physiology (1985) 2003-10, Vol.95 (4), p.1485-1492
• Main Authors: Shinohara, Minoru, Yoshitake, Yasuhide, Kouzaki, Motoki, Fukuoka, Hideoki, Fukunaga, Tetsuo
• Format: Article
• Language: English
• Subjects: Adult; Bed Rest; Biological and medical sciences; Electromyography; Fundamental and applied biological sciences. Psychology; Humans; Knee; Leg; Male; Motor Activity - physiology; Muscle Contraction; Muscle, Skeletal - physiology; Muscular system; Physical Education and Training; Torque; Weightlifting
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.01173.2002

1 Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309; 2 Department of Health Sciences, Oita University of Nursing and Health Sciences, Oita 870; 3 Department of Life Sciences, The University of Tokyo, Tokyo 153; 4 School of Medicine, The University of Tokyo, Tokyo 113; and 5 Department of Sport Sciences, Waseda University, Saitama 359, Japan Submitted 20 December 2002 ; accepted in final form 20 June 2003 The purpose of the study was to determine the effect of bed rest with or without strength training on torque fluctuations and activation strategy of the muscles. Twelve young men participated in a 20-day bed rest study. Subjects were divided into a non-training group (BRCon) and a strength-training group (BRTr). The training comprised dynamic calf-raise and leg-press exercises. Before and after bed rest, subjects performed maximal contractions and steady submaximal isometric contractions of the ankle extensor muscles and of the knee extensor muscles (2.5-10% of maximal torque). Maximal torque decreased for both the ankle extensors (9%, P < 0.05) and knee extensors (16%, P < 0.05) in BRCon but not in BRTr. For the ankle extensors, the coefficient of variation (CV) for torque increased in both groups ( P < 0.05), with a greater amount ( P < 0.05) in BRCon (88%) compared with BRTr (41%). For the knee extensors, an increase in the CV for torque was observed only in BRCon (22%). The increase in the CV for torque in BRCon accompanied the greater changes in electromyogram amplitude of medial gastrocnemius (122%) and vastus lateralis (59%) compared with BRTr ( P < 0.05). The results indicate that fluctuations in torque during submaximal contractions of the extensor muscles in the leg increase after bed rest and that strength training counteracted the decline in performance. The response varied across muscle groups. Alterations in muscle activation may lead to an increase in fluctuations in motor output after bed rest. steadiness; knee extension; plantarflexion; electromyogram Address for reprint requests and other correspondence: M. Shinohara, Dept. of Integrative Physiology, Univ. of Colorado, Boulder, CO 80309-0354 (E-mail: shinohara{at}colorado.edu ).