PASSIVE MECHANICAL PROPERTIES OF THE GASTROCNEMIUS AFTER SPINAL CORD INJURY

Introduction: In this study we compared passive mechanical properties of gastrocnemius muscle-tendon units, muscle fascicles, and tendons in control subjects and people with ankle contractures after spinal cord injury. Methods: Passive gastrocnemius length-tension curves were derived from passive ankle torque-angle data obtained from 20 spinal cord injured subjects with ankle contractures and 30 control subjects. Ultrasound images of muscle fascicles were used to partition length-tension curves into fascicular and tendinous components. Results: Spinal cord injured subjects had stiffer gastrocnemius muscle-tendon units (stiffness index: 74.8 +/- 27.0 m(-1)) than control subjects (54.4 +/- 17.7 m(-1)) (P = 0.004). Muscle-tendon slack lengths, as well as slack lengths and changes in length of fascicles and tendons, were similar in the two groups. Conclusions: People with ankle contractures after spinal cord injury have stiff gastrocnemius muscle-tendon units. It is not clear whether this reflects changes in properties of muscle fascicles or tendons. Muscle Nerve 46: 237-245, 2012