Change in the circulation and activity of the lower erector spinae muscles after repeated trunk extension movement

BACKGROUND: The optimum repetition number of standing back-extension exercise (SBEE) effective for the prevention and improvement of low back pain (LBP) is unknown. OBJECTIVE: To determine the effect of physiotherapy on LBP by investigating the optimum repetition number of SBEE via optical analysis and electromyographic (EMG) examination of the multifidus muscles. METHODS: Hemodynamics and multifidus muscle activity were examined in 16 healthy adult men using near-infrared spectroscopy and surface EMG after performing repetitive SBEE. RESULTS: Oxidized hemoglobin (Oxy-Hb) levels significantly increased in the second extension phase but decreased in the third and subsequent extension phases; deoxidized hemoglobin (deOxy-Hb) levels increased in the third and subsequent extension phases. In the standing phase, no significant difference was observed; in the third and subsequent phases, Oxy-Hb levels decreased and deOxy-Hb levels increased. Muscular activity significantly decreased in the second standing phase but increased in the third and subsequent phases. No significant difference was observed in the extension phase with respect to the number of SBEE repetitions performed. In healthy individuals, hemodynamics improved up to second repetition of SBEE; subsequent repetitions may decrease hemodynamics because of increased activity of the multifidus muscles. CONCLUSIONS: In healthy individuals, hemodynamics improved up to second repetition of SBEE.