Local loss of proprioception results in disruption of interjoint coordination during locomotion in the cat.

To investigate the role of localized, proprioceptive feedback in the regulation of interjoint coordination during locomotion, we substantially attenuated neural feedback from the triceps surae muscles in one hindlimb in each of four cats using the method of self-reinnervation. After allowing the recovery of motor innervation, the animals were filmed during level and ramp walking. Deficits were small or undetectable during walking on the level surface or up the ramp, behaviors that require a large range of forces in the triceps surae muscles. During walking down the ramp, when the triceps surae muscles normally undergo active lengthening, the ankle joint underwent a large yield and the coordination between ankle and knee was disrupted. The correlation of the deficit with the direction of length change and not muscle force suggested that a loss of feedback from muscle spindle receptors was primarily responsible for the deficit. These results indicate an important role for the stretch reflex and stiffness regulation during locomotion.

Tendon force measurements and movement control: a review.

Knowledge of the mechanical and electrical output from skeletal muscle is of interest to investigators from several disciplines including physiology, biomechanics, neuroscience, orthopedics, and physical rehabilitation. Estimates of muscle output (i.e., force) have generally been made using indirect calculations. Forward solution (e.g., EMG) and optimization models have recently been developed using a wide variety of input parameters to estimate force output of individual muscles. These estimates, however, have lacked comparison values necessary for validation. In vivo measurements of muscle force have been made in both animals and humans using a "buckle" type tendon transducer surgically implanted on the tendons of the muscles under study. Investigations utilizing these transducers have addressed a wide range of questions regarding muscle function. This review examines the use of this technology and discusses the significance of the future use of "buckle" transducers in studies exploring load sharing among muscles and in the validation of existing models that estimate muscle force.