Sandmann M E, Shoeman J A, Thompson L V
Department of Physical Medicine and Rehabilitation, School of Medicine, University of Minnesota, Minneapolis 55455, USA.
Arch Phys Med Rehabil. 1998 Jun;79(6):658-62. doi: 10.1016/s0003-9993(98)90040-5.
To characterize single skeletal muscle fiber contractile properties from the gastrocnemius muscle that occur during inactivity and intermittent weight-bearing in 30-month-old animals.
Randomized control trial.
A controlled laboratory environment.
Eighteen 30-month-old male Fisher 344 Brown Norway F1 Hybrid rats were randomly assigned to control (C), hindlimb unweighted (HU), and hindlimb unweighted with intermittent weight-bearing (HU-X) groups.
The HU and HU-X rats were suspended for 7 days. The HU-X animals were unsuspended for four 15-minute bouts of weight-bearing.
Single skeletal muscle fiber contractile properties (diameter, peak active force [P0], peak specific tension [P0/CSA], and maximal shortening velocity [V0] by fiber type) were determined from the deep portion of the lateral head of the gastrocnemius muscle (RG).
In comparison to C animals, the ratio of gastrocnemius weight to body weight decreased by 18% and 14% following HU and HU-X, respectively. Diameter and P0 of type I fibers from the RG were reduced after HU. Attenuation of the decline in diameter and P0 was observed in type I fibers from the RG with HU-X. P0 was reduced in type IIa fibers and type I-IIa fibers with HU. Attenuation of the decline in P0 by intermittent weight-bearing in type IIa fibers and type I-IIa fibers did not occur.
Inactivity altered the contractile properties of single skeletal muscle fibers from the gastrocnemius muscle of 30-month-old animals. The inactivity-induced alterations were present in the three fiber types. Therapeutic intervention of weight-bearing attenuated the inactivity-induced changes in the type I fibers from the gastrocnemius, but not the other fiber types.
表征30月龄动物在不活动和间歇性负重期间腓肠肌单根骨骼肌纤维的收缩特性。
随机对照试验。
受控实验室环境。
18只30月龄雄性Fisher 344 Brown Norway F1杂交大鼠被随机分配至对照组（C）、后肢去负荷组（HU）和后肢去负荷并间歇性负重组（HU-X）。
HU组和HU-X组大鼠悬吊7天。HU-X组动物进行4次每次15分钟的负重解除悬吊。
从腓肠肌外侧头深部（RG）测定单根骨骼肌纤维的收缩特性（直径、峰值主动力[P0]、峰值比张力[P0/CSA]和按纤维类型划分的最大缩短速度[V0]）。
与C组动物相比，HU组和HU-X组后腓肠肌重量与体重之比分别下降了18%和14%。HU组后RG的I型纤维直径和P0降低。在HU-X组的RG的I型纤维中观察到直径和P0下降的衰减。HU组IIa型纤维和I-IIa型纤维的P0降低。IIa型纤维和I-IIa型纤维通过间歇性负重并未出现P0下降的衰减。
不活动改变了30月龄动物腓肠肌单根骨骼肌纤维的收缩特性。不活动诱导的改变存在于三种纤维类型中。负重的治疗性干预减弱了腓肠肌I型纤维中不活动诱导的变化，但未减弱其他纤维类型的变化。
