由于缩放问题,随着肢体尺寸的减小,被动肌肉和关节力变得越来越重要。被动力可以驱动运动中的摆动,4,5和拮抗剂被动扭矩有助于控制肢体摆动速度。6在站立时,最小化对抗肌肉和关节被动力可以节省能量。这些考虑因素预测,对于小四肢,进化将导致角度范围,在该角度范围内,被动力太小,无法引起肢体运动(称为\“静止状态范围\”在先前的昆虫工作中4和\“中性平衡区域\”在物理和工程)与肢体的典型工作范围相关,通常在运动中。我们测量了前(前)最延长和最缩回的胸股骨(ThF)角度,中观-(中),竹节虫(Carausiusmorosus)行走时的胸(后)腿。ThF工作范围在三种腿类型中有所不同,在更多的后腿中更靠后。在其他实验中,我们手动延长或缩回去神经的前部,中间,和后腿。释放后,被动力沿相反的方向(缩回或伸出)移动腿,直到到达ThF静止状态范围内最延长或最缩回的边缘。ThF静止状态角度范围与腿型工作范围相关,在更多的后腿中更靠后。最长时间的ThF行走角度比伸出后的ThF角度更缩回,收缩最大的ThF行走角度与收缩后的ThF角度相似。ThF工作状态和静息状态范围的这些相关性可以简化电机控制并节省能源。这些数据还提供了通过改变被动肌肉和关节特性来改变行为的进化例子。
Because of scaling issues, passive muscle and joint forces become increasingly important as limb size decreases.1-3 In some small limbs, passive forces can drive swing in locomotion,4,5 and antagonist passive torques help control limb swing velocity.6 In stance, minimizing antagonist muscle and joint passive forces could save energy. These considerations predict that, for small limbs, evolution would result in the angle range over which passive forces are too small to cause limb movement (called \"resting-state range\" in prior insect work4 and \"area of neutral equilibrium\" in physics and engineering) correlating with the limb\'s typical working range, usually that in locomotion. We measured the most protracted and retracted thorax-femur (ThF) angles of the pro- (front), meso- (middle), and metathoracic (hind) leg during stick insect (Carausius morosus) walks. This ThF working range differed in the three leg types, being more posterior in more posterior legs. In other experiments, we manually protracted or retracted the denervated front, middle, and hind legs. Upon release, passive forces moved the leg in the opposite direction (retraction or protraction) until it reached the most protracted or most retracted edge of the ThF resting-state range. The ThF resting-state angle ranges correlated with the leg-type working range, being more posterior in more posterior legs. The most protracted ThF walking angles were more retracted than the post-protraction ThF angles, and the most retracted ThF walking angles were similar to the post-retraction ThF angles. These correlations of ThF working- and resting-state ranges could simplify motor control and save energy. These data also provide an example of evolution altering behavior by changing passive muscle and joint properties.7.