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Deterioration of Muscle Function after 21-Day Forearm Immobilization

KITAHARA, AYA; HAMAOKA, TAKAFUMI; MURASE, NORIO; HOMMA, TOSHIYUKI; KUROSAWA, YUKO; UEDA, CHIHOKO; NAGASAWA, TAKESHI; ICHIMURA, SHIRO; MOTOBE, MAYUKO; YASHIRO, KAZUYA; NAKANO, SHOUICHI; KATSUMURA, TOSHIHITO

Medicine & Science in Sports & Exercise: October 2003 - Volume 35 - Issue 10 - p 1697-1702
doi: 10.1249/01.MSS.0000089339.07610.5F
BASIC SCIENCES: Original Investigations

KITAHARA, A., T. HAMAOKA, N. MURASE, T. HOMMA, Y. KUROSAWA, C. UEDA, T. NAGASAWA, S. ICHIMURA, M. MOTOBE, K. YASHIRO, S. NAKANO, and T. KATSUMURA. Deterioration of Muscle Function after 21-Day Forearm Immobilization. Med. Sci. Sports Exerc., Vol. 35, No. 10, pp. 1697–1702, 2003.

Purpose Although it is well known that immobilization causes muscle atrophy, most immobilization models have examined lower limbs, and little is known about the forearm. The purpose of this study was to determine whether forearm immobilization produces changes in muscle morphology and function.

Methods Six healthy males (age: 21.5 ± 1.4, mean ± SD) participated in this study. The nondominant arm was immobilized with a cast (CAST) for 21 d, and the dominant arm was measured as the control (CONT). The forearm cross-sectional area (CSA) and circumference were measured as muscle morphology. Maximum grip strength, forearm muscle oxidative capacity, and dynamic grip endurance were measured as muscle function. Magnetic resonance (MR) imaging was used to measure CSA, and 31phosphorus MR spectroscopy was used to measure time constant (Tc) for phosphocreatine (PCr) recovery after submaximal exercise (PCr-Tc). Grip endurance was expressed by the number of handgrip contractions at 30% maximum grip strength load. All measurements were taken before and after the immobilization.

Results After the 21-d forearm immobilization, no changes were seen for each measurement in CONT. CSA and the circumference showed no significant changes in CAST. However, maximum grip strength decreased by 18% (P < 0.05), PCr-Tc was prolonged by 45% (P < 0.05), and the grip endurance at the absolute load was reduced by 19% (P < 0.05) for CAST.

Conclusion In this model, 21-d forearm immobilization caused no significant changes in forearm muscle morphology, but the muscle function showed remarkable deterioration ranging from 18 to 45%.

Department of Preventive Medicine and Public Health, Tokyo Medical University; National Institute of Fitness and Sports and Nippon Sport Science University, JAPAN

Address for correspondence: Aya Kitahara, M.D., Department of Preventive Medicine and Public Health, Tokyo Medical University, 6-1-1, Shinjuku, Shinjuku-ku, Tokyo 160-8402 Japan; E-mail: Ayakitahar@aol.com.

Submitted for publication March 2003.

Accepted for publication June 2003.

©2003The American College of Sports Medicine