Burkholder T J, Lieber R L
Department of Orthopaedics, University of California, Medical Center, San Diego 92161, USA.
J Exp Biol. 1998 Feb;201(Pt 3):309-16.
Skeletal muscle has been shown to adjust serial sarcomere number in response to chronic static length changes. However, the adaptive responses to alterations in the dynamic environment are less well defined. The adaptations of the adult mouse tibialis anterior (TA) muscle to altered length and excursion were investigated by surgical transection of the flexor retinaculum. TA moment arm and muscle excursion increased by 38 +/- 7% (mean +/- S.E.M.) and fully extended (plantarflexed) muscle length was decreased by 8% after flexor retinaculum transection. In spite of the significant shortening of the muscle in full plantar- and dorsiflexion, serial sarcomere number decreased by 10 +/- 1% after 2 weeks of recovery. Gait analysis of these transected animals revealed a 14 +/- 3% decrease in dorsiflexion angular velocity after transection. The decrease in angular velocity was less than the increase in moment arm and, as a result, muscle velocity was calculated to increase by 20 +/- 4%. These data suggested that the muscle adapted in response to the underlying change in length, irrespective of the altered excursion or velocity.
已证明骨骼肌会根据慢性静态长度变化来调整串联肌节数量。然而，对动态环境变化的适应性反应却不太明确。通过手术切断屈肌支持带，研究成年小鼠胫前肌（TA）对长度和移动幅度改变的适应性。切断屈肌支持带后，TA的力臂和肌肉移动幅度增加了38±7%（平均值±标准误），完全伸展（跖屈）时的肌肉长度减少了8%。尽管在完全跖屈和背屈时肌肉明显缩短，但恢复2周后串联肌节数量减少了10±1%。对这些切断屈肌支持带的动物进行步态分析发现，切断后背屈角速度降低了14±3%。角速度的降低小于力臂的增加，因此，计算得出肌肉速度增加了20±4%。这些数据表明，肌肉是根据长度的潜在变化进行适应的，而与移动幅度或速度的改变无关。
