Electromyographic activity of the trunk extensor muscles: effect of varying hip position and lumbar posture during Roman chair exercise.

OBJECTIVE: To evaluate the effect of hip position and lumbar posture on the surface electromyographic activity of the trunk extensors during Roman chair exercise.

DESIGN: Descriptive, repeated measures.

SETTING: University-based musculoskeletal research laboratory.

PARTICIPANTS: Twelve healthy volunteers (7 men, 5 women; age range, 18-35y) without a history of low back pain were recruited from a university setting.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Surface electromyographic activity was recorded from the lumbar extensor, gluteal, and hamstring musculature during dynamic Roman chair exercise. For each muscle group, electromyographic activity (mV/rep) was compared among exercises with internal hip rotation and external hip rotation and among exercises by using a typical lumbar posture (nonbiphasic) and a posture that accentuated lumbar lordosis (biphasic).

RESULTS: For the lumbar extensors, electromyographic activity during exercise was 18% greater with internal hip rotation than external hip rotation (P< or =.05) and was 25% greater with a biphasic posture than with a nonbiphasic posture (P< or =.05). For the gluteals and hamstrings, there was no difference in electromyographic activity between internal and external hip rotation or between biphasic and nonbiphasic postures (P >.05).

CONCLUSION: The level of recruitment of the lumbar extensors can be modified during Roman chair exercise by altering hip position and lumbar posture. Clinicians can use these data to develop progressive exercise protocols for the lumbar extensors with a variety of resistance levels without the need for complex equipment.