Kitahara Aya, Hamaoka Takafumi, Murase Norio, Homma Toshiyuki, Kurosawa Yuko, Ueda Chihoko, Nagasawa Takeshi, Ichimura Shiro, Motobe Mayuko, Yashiro Kazuya, Nakano Shouichi, Katsumura Toshihito
Department of Preventive Medicine and Public Health, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
Med Sci Sports Exerc. 2003 Oct;35(10):1697-702. doi: 10.1249/01.MSS.0000089339.07610.5F.
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.
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.
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.
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%.
尽管众所周知固定会导致肌肉萎缩，但大多数固定模型研究的是下肢，而对前臂的了解甚少。本研究的目的是确定前臂固定是否会导致肌肉形态和功能发生变化。
六名健康男性（年龄：21.5±1.4，平均值±标准差）参与了本研究。将非优势手臂用石膏固定（CAST组）21天，将优势手臂作为对照进行测量（CONT组）。测量前臂横截面积（CSA）和周长作为肌肉形态指标。测量最大握力、前臂肌肉氧化能力和动态握力耐力作为肌肉功能指标。使用磁共振（MR）成像测量CSA，使用31磷磁共振波谱测量次最大运动后磷酸肌酸（PCr）恢复的时间常数（Tc）（PCr-Tc）。握力耐力用在最大握力负荷30%时的握力收缩次数表示。所有测量均在固定前后进行。
在21天的前臂固定后，CONT组的各项测量指标均未发生变化。CAST组的CSA和周长无显著变化。然而，CAST组的最大握力下降了18%（P<0.05），PCr-Tc延长了45%（P<0.05），绝对负荷下的握力耐力降低了19%（P<0.05）。
在该模型中，21天的前臂固定未导致前臂肌肉形态发生显著变化，但肌肉功能出现了18%至45%的显著恶化。
