Larsson L, Ansved T
Muscle Nerve. 1985 Oct;8(8):714-22. doi: 10.1002/mus.880080815.
The adaptability of human skeletal muscle to increased (training) and decreased (detraining) usage was studied in 11 athletes over a 42-month-long observation period. Biopsies were taken from the deltoid and the quadriceps muscle, together with measurements of maximum torque output during voluntary knee extensions at high relative to slow speeds of movement. A 16% and 14% decrease in the proportion of type I fibers was seen in the proximal arm and leg muscles, respectively, in the detraining subjects. This conformed with the changes in muscle function. On the other hand, in the training subjects, who increased their activity level through systematic daily physical training over an almost 4-year-long period, there were no significant changes seen in fiber type proportions of either arm or leg muscles. This was presumably due to the smaller net change in physical activity level caused by training as compared to detraining in the subjects of this study. Thus, the results show that fiber type proportions in intact human skeletal muscle are not exclusively determined by heredity, but may also be influenced by environmental factors, such as physical activity level.
在42个月的观察期内，对11名运动员进行了研究，以了解人类骨骼肌对增加（训练）和减少（停训）使用的适应性。从三角肌和股四头肌取活检样本，并测量在高运动速度相对于低运动速度的自愿膝关节伸展过程中的最大扭矩输出。在停训的受试者中，近端手臂和腿部肌肉中I型纤维的比例分别下降了16%和14%。这与肌肉功能的变化相符。另一方面，在通过近4年的系统日常体育训练提高了活动水平的训练受试者中，手臂或腿部肌肉的纤维类型比例没有显著变化。这可能是由于与本研究中的停训受试者相比，训练引起的身体活动水平净变化较小。因此，结果表明，完整人类骨骼肌中的纤维类型比例并非完全由遗传决定，还可能受到身体活动水平等环境因素的影响。
