Reilly S M
Department of Biological Sciences, Ohio University, Athens, Ohio 45701, USA.
Brain Behav Evol. 1998;52(3):126-38. doi: 10.1159/000006557.
Previous kinematic analyses in Sceloporus clarkii have shown that increased speed during trotting is attained by retracting the femur relatively faster (decreasing retraction time relative to stride duration) while all other aspects of axial and limb movements occur simply faster (scaling with stride duration). Thus, most of the limb muscles must be modulated to move the joints absolutely faster, while muscles effecting femoral retraction must be modulated differently to retract the femur relatively faster to increase speed. This prediction was examined by analyzing motor patterns in several key leg muscles in the spiny lizard running over a threefold increase in speed during a trot. The prediction is borne out in the limb muscles where the limb adductor (flexor tibialis), knee extender (femorotibialis), and plantar flexor of the ankle (gastrocnemius) have similar patterns of motor modulation that are different from that of the femoral retractor (caudofemoralis). To modulate a muscle to move simply faster (scaled with speed) the offset of the motor pattern is moved relatively earlier to decrease burst duration, while the intensity of electromyographical activation is ramped up. Increasing the relative speed of action is done by activating the muscle earlier, increasing the duration of the burst, and increasing the relative level of activation. Comparisons to other studies illustrate that the confounding effects that stance and swing duration have on stride duration with speed have important consequences for functional interpretations and that scaling locomotory data to stance duration is a more appropriate and useful convention because it relates information directly to the duty cycle when the propulsive effects of motor modulation are transmitted to the substrate. The iliocostalis in Sceloporus clarkii has a pattern of activity indicating that it functions to rotate the pelvis to aid the contralateral duty cycle. This is strikingly different from the function of the iliocostalis in the monitor lizard. Differences in axial function and differences among lizards in postures of the foot and crus during locomotion indicate that there are different ways that lizards run and that the functional and anatomical diversity of modes of locomotion in lizards is greater than is recognized at present.
先前对克拉克强棱蜥的运动学分析表明，在小步跑过程中，速度的提升是通过相对更快地收回股骨（相对于步幅持续时间缩短收回时间）实现的，而轴向和肢体运动的所有其他方面只是简单地变快（与步幅持续时间成比例）。因此，大多数肢体肌肉必须被调节以绝对更快地移动关节，而影响股骨收回的肌肉必须以不同方式被调节，以便相对更快地收回股骨以提高速度。通过分析棘蜥在小步跑过程中速度提高三倍时几条关键腿部肌肉的运动模式，对这一预测进行了检验。这一预测在肢体肌肉中得到了证实，其中肢体内收肌（胫屈肌）、伸膝肌（股胫肌）和踝关节跖屈肌（腓肠肌）具有相似的运动调节模式，这与股骨牵缩肌（尾股肌）不同。为了调节一块肌肉使其简单地变快（与速度成比例），运动模式的偏移会相对提前，以减少爆发持续时间，同时肌电图激活强度会增加。通过更早地激活肌肉、增加爆发持续时间以及增加相对激活水平来提高动作的相对速度。与其他研究的比较表明， stance和摆动持续时间对步幅持续时间与速度的混杂影响对功能解释具有重要影响，并且将运动数据按 stance持续时间进行缩放是一种更合适且有用的惯例，因为它将信息直接与运动调节的推进效应传递到基质时的占空比相关联。克拉克强棱蜥的髂肋肌具有一种活动模式，表明它的功能是旋转骨盆以辅助对侧的占空比。这与巨蜥中髂肋肌的功能显著不同。轴向功能的差异以及蜥蜴在运动过程中足部和小腿姿势的差异表明，蜥蜴有不同的奔跑方式，并且蜥蜴运动模式的功能和解剖学多样性比目前所认识到的更大。
