Terjung R L
Am J Physiol. 1976 Apr;230(4):946-50. doi: 10.1152/ajplegacy.1976.230.4.946.
The extent of skeletal muscle fiber type involvement during exercise training was evaluated by assessing the increase in oxidative markers in the muscles of rats trained by various exercise programs. Rats were trained by running 6 days/wk at 1 mph for 12 wk by one of four protocols: group I-10% grade, 2 h/day; group II-10% grade, 4 h/day; group III-30% grade, 40 min/day; and group IV-30% grade, 2 h/day. No distinction was found between the different programs for the increase in cytochrome c content or citrate synthase (CS) activity of mixed muscle. The more intense programs utilizing a 30% grade induced an increase in CS activity in the fast-twitch white (FTW) fiber that was twice that found in the 10% grade groups. The fast-twitch red (FTR) fibers of the 2 h/day or more groups showed a similar increase (90-95%) in CS activity except for the group that ran for only 40 min/day. These data suggest that: 1) running durations of moderately intense exercise longer than 2 h/day do not further increase the oxidative capacity of the working muscles; and 2) more intense exercise builds on the performance of previously used FTR fibers and additionally involves the low oxidative FTW fibers.
通过评估不同运动方案训练的大鼠肌肉中氧化标志物的增加情况，来评估运动训练期间骨骼肌纤维类型的参与程度。大鼠按以下四种方案之一进行训练：每周6天，以1英里/小时的速度跑步12周，I组坡度为10%，每天2小时；II组坡度为10%，每天4小时；III组坡度为30%，每天40分钟；IV组坡度为30%，每天2小时。在混合肌肉的细胞色素c含量或柠檬酸合酶（CS）活性增加方面，不同方案之间未发现差异。使用30%坡度的更剧烈运动方案使快肌白纤维（FTW）中的CS活性增加，是10%坡度组的两倍。每天运动2小时或更长时间的组中，快肌红纤维（FTR）的CS活性也有类似增加（90 - 95%），只有每天跑步仅40分钟的组除外。这些数据表明：1）每天超过2小时的中等强度运动持续时间不会进一步提高工作肌肉的氧化能力；2）更剧烈的运动在先前使用的FTR纤维的基础上提高其性能，并且还涉及低氧化能力的FTW纤维。
