Dynamic testing of the motor stereotype in prone hip extension from neutral position.
OBJECTIVE: The purpose of the study was to identify a sequential activation of lumbar and hip muscles in active prone hip extension from neutral position in subjects without a history of low back pain. DESIGN: Using surface electromyography, the myoelectric activity onsets of agonistic and antagonistic hip muscles were recorded. BACKGROUND: The development of low back pain is ascribed to changes of the muscle firing order in prone hip extension. There appeared to be no normative data on muscle firing order of the lumbar and hip musculature to provide a basis for recognizing variations. METHODS: Fifteen healthy subjects performed standardized right hip extensions. Time-normalized onset of EMG activity in each muscle was measured for each trial. RESULTS: A MANOVA revealed significant (P < 0.01) differences between the activity onsets of synergistic muscles in hip extension. CONCLUSIONS: On the results it was concluded that the consistent muscle firing order of ipsilateral lumbar erector spinae, semitendinosus, contralateral lumbar erector spinae, tensor fasciae latae, and gluteus maximus demonstrate the characteristic pattern in prone hip extension. In future studies it is essential to evaluate also the hip extension pattern in functional upright conditions during gait and their relationship to spinal mechanics.