White M J, Davies C T
Clin Sci (Lond). 1984 Mar;66(3):277-82. doi: 10.1042/cs0660277.
The contractile properties of the triceps surae were evaluated in 11 patients after unilateral fracture of the lower leg and subsequent immobilization for 135 +/- 68 days. Calf muscle cross-sectional area (plus bone: CSA) was assessed from anthropometric measurement. It was shown that the injured leg had a faster time to peak tension and increased half-relaxation time (1/2 RT); twitch force (Pt) was reduced by 25%. Evoked maximal tetanic tensions (Po) at 10 and 20 Hz were reduced by 51% and 46% respectively compared with the uninjured leg. The force of a maximal voluntary contraction (MVC) was also reduced, by 50%, but calf circumference and CSA were only 5% and 16% respectively lower in the injured leg. It was concluded that the changes in contractile speed may indicate a relatively greater atrophy of slow (type I) muscle fibres. The relationship between CSA and tension generation in the injured limb was shown to be poor after immobilization and during recovery. Anthropometric estimation of CSA does not appear to reflect the degree of muscle wasting, as indicated by reduced tension development after immobilization.
对11例单侧小腿骨折并随后固定135±68天的患者的小腿三头肌收缩特性进行了评估。通过人体测量评估小腿肌肉横截面积（包括骨骼：CSA）。结果显示，受伤腿达到峰值张力的时间更快，半松弛时间（1/2 RT）增加；单收缩力（Pt）降低了25%。与未受伤腿相比，在10 Hz和20 Hz时诱发的最大强直张力（Po）分别降低了51%和46%。最大自主收缩（MVC）力也降低了50%，但受伤腿的小腿周长和CSA仅分别低5%和16%。得出的结论是，收缩速度的变化可能表明慢肌（I型）纤维萎缩相对更严重。在固定期间和恢复过程中，受伤肢体的CSA与张力产生之间的关系较差。如固定后张力发展降低所示，通过人体测量对CSA的估计似乎不能反映肌肉萎缩的程度。
