The passive extensibility of skeletal muscles is an important health-related component of physical fitness. Tight gastrocnemius is a common orthopedic problem and frequently leads to overuse injuries of the lower extremity. Moreover, gastrocnemius tightness is commonly associated with lower back pain. Previous studies have reported that tight gastrocnemius results in kinematic and kinetic deviations of the ankle and knee during gait and a greater hip flexion at the moment of maximal ankle dorsiflexion. Accordingly, this study performs an experimental investigation into the effects of tight gastrocnemius on the hip and pelvic movements in gait. Sixteen subjects with tight gastrocnemius (defined as <10∘ of ankle dorsiflexion with knee extended) and 16 healthy individuals matched by age and gender participated in the study. The three-dimensional angles of the hip and pelvis and moments of the hip were obtained for both groups during the stance phase of gait using force plates and a motion analysis system. Compared with the control group, the peak hip flexion angle is significantly higher in the tight group (p=0.001), while the peak hip extension angle is significantly lower (p=0.001). Moreover, the peak pelvic anterior tilt is significantly higher than that of the control group (p=0.001), while the peak pelvic posterior tilt is significantly lower (p=0.001). Finally, the peak extensor moment of the tight group is significantly higher than that of the control group (p=0.049), while the peak flexor moment is significantly lower (p=0.003). The results confirm that tight gastrocnemius leads to changes in the three-dimensional hip and pelvic angles and hip moments during gait. Disturbance of the hip and pelvic movement is thus a critical clinical consideration when evaluating soft tissue injuries in patients with tight gastrocnemius.
