Alway S E, Sale D G, MacDougall J D
School of Health, Physical Education and Recreation, Ohio State University, Columbus 43210-1284.
Eur J Appl Physiol Occup Physiol. 1990;60(5):346-52. doi: 10.1007/BF00713497.
Ultrastructural and twitch contractile characteristics of the human triceps surae were determined in six healthy but very sedentary subjects before and after 16 weeks of isometric training at 30% maximal voluntary contraction (MVC). Following training, twitch contraction time was approximately 16% shorter, although no differences were observed in one-half relaxation time or peak twitch torque. Percent fibre type was not changed by training. The mean area of type I and type II fibres in the soleus increased by approximately 30% but only type II fibres showed an increase in area in the lateral gastrocnemius (30%). Despite such changes in fibre area the volume density of the sarcoplasmic reticulum-transverse tubular network averaged 3.2 +/- 0.6% and 5.9 +/- 0.9% in type I and type II fibres respectively, before and after training in the two heads of the gastrocnemius. The results indicate that contractile adaptations to isometric training at 30% MVC were limited to twitch contraction time and were not directly related to changes in percent fibre distribution or the volume of sarcoplasmic reticulum and transverse tubules in either type I or type II fibres. The data further demonstrate that substantial fibre hypertrophy is achieved by training with low-intensity contractions.
在六名健康但久坐不动的受试者中，测定了他们在以最大自主收缩（MVC）的30%进行16周等长训练前后，小腿三头肌的超微结构和抽搐收缩特征。训练后，抽搐收缩时间缩短了约16%，尽管在半松弛时间或抽搐峰值扭矩方面未观察到差异。训练并未改变纤维类型百分比。比目鱼肌中I型和II型纤维的平均面积增加了约30%，但只有外侧腓肠肌中的II型纤维面积增加（30%）。尽管纤维面积发生了这些变化，但在腓肠肌两个头训练前后，I型和II型纤维中肌浆网 - 横管网络的体积密度分别平均为3.2 +/- 0.6%和5.9 +/- 0.9%。结果表明，在30%MVC下进行等长训练时，收缩适应仅限于抽搐收缩时间，与I型或II型纤维中纤维分布百分比的变化或肌浆网和横管的体积没有直接关系。数据进一步证明，通过低强度收缩训练可实现显著的纤维肥大。
