Gastrocnemius Medialis Contractile Behavior Is Preserved During 30% Body Weight Supported Gait Training

Abstract

Rehabilitative body weight supported gait training aims at restoring walking function as a key element in activities of daily living. Studies demonstrated reductions in muscle and joint forces, while kinematic gait patterns seem to be preserved with up to 30% weight support. However, the influence of body weight support on fascicle and series elastic element behavior is unknown, despite this having potentially clinical implications for gait retraining. Eight males (31.9 ± 4.7 yrs) walked at 75% of their preferred walk-to-run transition speeds with 0% and 30% body weight support on a lower-body positive pressure treadmill. Gastrocnemius medialis fascicle lengths and pennation angles were measured via ultrasonography. Joint kinematics were analyzed to determine muscle−tendon unit lengths. Series elastic element length was assessed using a muscle−tendon unit model. Depending on whether data were normally distributed, a paired t-test or Wilcoxon signed rank test was performed to determine if body weight supported walking had any effects on joint kinematics and fascicle−series elastic element behavior. Walking with 30% body weight support had no statistically significant effect on joint kinematics and peak series elastic element length. Furthermore, at the time when peak series elastic element length was achieved and on average across the entire stance phase, muscle−tendon unit length, fascicle length, pennation angle and fascicle velocity were unchanged in addition to overall fascicle shortening. In accordance with unchanged gait kinematics, preservation of fascicle−series elastic element behavior was observed during walking with 30% body weight support that suggests transferability of gait patterns to subsequent unsupported walking.