Larsen G S, Frazier S F, Fish S E, Zill S N
Department of Anatomy, Cell and Neurobiology, Marshall University School of Medicine, Huntington, WV 25755.
J Comp Physiol A. 1995 Feb;176(2):229-38. doi: 10.1007/BF00239925.
To examine how walking patterns are adapted to changes in load, we recorded leg movements and muscle activities when cockroaches (Periplaneta americana) walked upright and on an inverted surface. Animals were videotaped to measure the hindleg femoro-tibial joint angle while myograms were taken from the tibial extensor and flexor muscles. The joint is rapidly flexed during swing and extended in stance in upright and inverted walking. When inverted, however, swing is shorter in duration and the joint traverses a range of angles further in extension. In slow upright walking, slow flexor motoneurons fire during swing and the slow extensor in stance, although a period of co-contraction occurs early in stance. In inverted walking, patterns of muscle activities are altered. Fast flexor motoneurons fire both in the swing phase and early in stance to support the body by pulling the animal toward the substrate. Extensor firing occurs late in stance to propel the animal forward. These findings are discussed within the context of a model in which stance is divided into an early support and subsequent propulsion phase. We also discuss how these changes in use of the hindleg may represent adaptations to the reversal of the effects of gravity.
为了研究行走模式如何适应负荷变化，我们记录了蟑螂（美洲大蠊）直立行走和在倒置表面行走时的腿部运动及肌肉活动。对动物进行录像以测量后肢股胫关节角度，同时记录胫部伸肌和屈肌的肌电图。在直立行走和倒置行走时，关节在摆动期迅速弯曲，在站立期伸展。然而，当倒置时，摆动持续时间较短，且关节在伸展时跨越的角度范围更大。在缓慢的直立行走中，慢屈肌运动神经元在摆动期放电，慢伸肌在站立期放电，尽管在站立早期会出现一段共同收缩期。在倒置行走时，肌肉活动模式发生改变。快屈肌运动神经元在摆动期和站立早期均放电，通过将动物拉向基质来支撑身体。伸肌在站立后期放电以推动动物前进。我们在一个将站立分为早期支撑和随后推进阶段的模型背景下讨论这些发现。我们还讨论了后肢使用方式的这些变化如何可能代表对重力影响逆转的适应。
