Postural constraints for two forms of quadrupedal walking

Summary form only given. Quadrupeds exhibit several forms of locomotion. One area of study is the demands made on the nervous system to meet the constraints of different forms. Two forms of walking, forward (FWD) and backward (BWD), in cats trained to walk on a treadmill (0.6 m/s) are discussed. It is shown that the basic muscle synergies are the same for both forms: extensors are active during stance and flexors during swing. Although synergies during the step cycle are similar, the timing and EMG amplitude, as well as the limb kinematics, are form specific. During FWD walking, for example, the hip extended during stance while the hip flexed during BWD stance. Thus, single-joint muscles such as the anterior biceps femoris, active during stance, shorten during FWD stance and lengthen during BWD stance, and feedback from hip joint and myotatic receptors are different even though the motor output is similar. It is postulated that BWD walking is possible only when the quadruped is able to set appropriate posture.<>