Hindlimb extensor muscle function during jumping and swimming in the toad (Bufo marinus).
Hindlimb extensor muscle function during jumping and swimming in the toad (Bufo marinus).
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发表时间：
2000-12
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通讯作者：
G. Gillis;A. Biewener
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作者：
G. Gillis;A. Biewener
许多无尾动物在跳跃和游泳时使用后肢产生推进力。为了研究在这种不同的物理环境中运动的肌肉骨骼动力学和运动输出，我们分别使用声测法和肌电图检查了蟾蜍在跳跃和游泳期间的肌肉应变和活动模式。我们测量了四个后肢肌肉的应变和肌电图 (EMG) 活动：半膜肌、髋伸肌；跖肌，踝关节伸肌；还有臀肌和小腿肌，两个膝伸肌。在跳跃过程中，这四块肌肉几乎同时被激活；然而，关节伸展似乎在时间上交错，髋部开始伸展先于更远端的膝关节和踝关节，或者最初比更远端的膝关节和踝关节伸展得更快。与这种模式相呼应的是，在起飞过程中肢体伸展的前半段，臀肌和跖肌会相当缓慢地缩短一小段距离，然后才开始迅速缩短。髋部和膝部伸肌在起跳点附近（当脚离开地面时）完成缩短，而踝关节伸展跖肌（平均而言，肌电图爆发持续时间最长）总是在起跳后完成缩短（平均 26 毫秒）。在游泳过程中，四块肌肉的激活在推进划水开始时也几乎是同步的。肌束缩短的开始在时间上是交错的，膝伸肌首先开始缩短，然后是髋部和踝部伸肌。此外，在肌电图活动开始之前，膝伸肌也经常表现出某种程度的缓慢被动缩短。游泳时肌肉缩短的偏移量也是交错的，并且比跳跃时的程度要大得多。游泳期间，小腿肌和臀肌首先完成缩短，半膜肌在 30-60 毫秒后完成，而跖肌（再次表现出最长的 EMG 爆发）最后完成缩短（平均在小腿肌之后 150 毫秒）。有趣的是，跖肌的这种延长的缩短大部分以相对较慢的速度发生，并且可能反映了由流体力引起的被动踝关节伸展，与先前产生的作用于足部的不稳定（加速）肢体运动相关。除了臀肌之外，所有肌肉在跳跃时的平均肌电图爆发强度往往比游泳时更大。然而，肌电图爆发持续时间仅在跳跃和游泳之间发生变化（跳跃期间的持续时间几乎是游泳期间的两倍）。腿肌也是唯一在跳跃期间（平均 0.28）比游泳期间（平均 0.20 主动应变，0.22 总应变）表现出更大缩短分数的肌肉。根据这些结果，蟾蜍后肢功能在跳跃和游泳之间发生了变化。此外，这些功能差异受到与外部环境之间的物理差异相关的被动效应的影响，但也受到一些肌肉的运动输出和机械行为的变化的主动调节。
Many anurans use their hindlimbs to generate propulsive forces during both jumping and swimming. To investigate the musculoskeletal dynamics and motor output underlying locomotion in such physically different environments, we examined patterns of muscle strain and activity using sonomicrometry and electromyography, respectively, during jumping and swimming in the toad Bufo marinus. We measured strain and electromyographic (EMG) activity in four hindlimb muscles: the semimembranosus, a hip extensor; the plantaris, an ankle extensor; and the gluteus and cruralis, two knee extensors. During jumping, these four muscles are activated approximately simultaneously; however, joint extension appears to be temporally staggered, with the hip beginning to extend prior to or initially faster than the more distal knee and ankle joints. Mirroring this pattern, the gluteus and plantaris shorten quite slowly and over a small distance during the first half of limb extension during take-off, before beginning to shorten rapidly. The hip and knee extensors finish shortening near the point of take-off (when the feet leave the ground), while the ankle-extending plantaris, which exhibits the longest-duration EMG burst, on average, always completes its shortening after take-off (mean 26 ms). During swimming, activation of the four muscles is also nearly synchronous at the start of a propulsive stroke. The onset of fascicle shortening is temporally staggered, with the knee extensors beginning to shorten first, prior to the hip and ankle extensors. In addition, the knee extensors also often exhibit some degree of slow passive shortening prior to the onset of EMG activity. The offset of muscle shortening during swimming is also staggered, and to a much greater extent than during jumping. During swimming, the cruralis and gluteus finish shortening first, the semimembranosus finishes 30-60 ms later, and the plantaris, which again exhibits the longest EMG burst, finishes shortening last (mean 150 ms after the cruralis). Interestingly, much of this extended shortening in the plantaris occurs at a relatively slow velocity and may reflect passive ankle extension caused by fluid forces, associated with previously generated unsteady (accelerative) limb movements, acting on the foot. Average EMG burst intensity tends to be greater during jumping than during swimming in all muscles but the gluteus. However, EMG burst duration only changes between jumping and swimming in the cruralis (duration during jumping is nearly twice as long as during swimming). The cruralis is also the only muscle to exhibit substantially greater fractional shortening during jumping (mean 0.28) than during swimming (mean 0.20 active strain, 0.22 total strain). On the basis of these results, it appears that toad hindlimb function is altered between jumping and swimming. Moreover, these functional differences are influenced by passive effects associated with physical differences between the external environments, but are also actively mediated by shifts in the motor output and mechanical behavior of several muscles.