EMG activity and force during prone hip extension in individuals with lumbar segmental instability

The goal of the current study was to investigate potential differences in back and hip extensor muscle activity and hip extension force during prone hip extension (PHE) in individuals with lumbar segmental instability (LSI) and asymptomatic subjects. Thirty-six subjects with LSI and 26 asymptomatic volunteers participated in this study. Muscle activity of the erector spinae, gluteus maximus, and biceps femoris was recorded using electromyography (EMG), and hip extension force was measured by a digital force gauge. Muscle activity was significantly greater in subjects with LSI than in asymptomatic subjects during PHE (p < 0.05). Hip extension force was significantly lower in the subjects with LSI than in asymptomatic subjects during PHE (p < 0.05). These findings suggest that during PHE, subjects with LSI have differences in back and hip extensor muscle activity and hip extension force compared to asymptomatic individuals.