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SURFACE EMG COMPARISON OF ISOMETRIC POSTERIOR CHAIN EXERCISE IN TORQUE MATCHED CONDITIONS

BD Justice

Abstract

Blake D. Justice. Methodist University, Fayetteville, NC.

BACKGROUND: Low Back Pain (LBP) is the second most common cause of disability in the U. S., with approximately 80% of adults experiencing low back pain at some point in their lives. In order to best treat LBP, exercises should selectively target the impaired muscle groups. The Reverse Hyperextension (RH) exercise allows an individual to strengthen the posterior chain while simultaneously providing extrinsic stabilization of the abdomen and spinal column. Alternatively, the traditional Back Extension (BE) allows strengthening with the lower extremities stationary on a supported surface, and the torso hinging in an open chain position through flexion and extension. This study assessed the activation of spinal erectors utilizing the RH and BE when the two exercises are matched for hip torque and hip angle. METHODS: Maximal trunk extension effort was collected performing Biering-Soransen test on standard high plinth with counter stabilization placed mid gastrocnemius. Downward force was applied to the trunk at the level of spine of scapula for duration of 5 second for a series of 3 trials. Isometric RH and BE were performed at hip angles of 120, 140, 160, and 180 degrees of extension with hip angles measured manually using an inclinometer. Torques about the hip for the RH and the BE at each desired posture were matched using anthropometric tables and equations for static equilibrium. Data analysis compared surface EMG amplitude of the iliocostalis, longissimus, and multifidus at the 4 hip angles. A two-way within-subjects ANOVA was performed to compare exercise and angles. RESULTS: The RH elicited a significant increase in muscle activation for the longissimus thoracis at all angles, when compared to the BE (F(1,19) = 117.24); p<0.05). A main effect was present for exercise for the left and right illiocostalis (F(1, 19) = 35.74, p<0.05; F(1,19) = 19.61, p<0.05 , respectively) and for angle at 120 (F(1,19) = 49.96, p<0.05) and 180 (F(1,19) = 41.52 , p<0.05) degrees. There was not a significant difference in multifidus activation between the two exercises. The most significant difference in muscle activation occurred at 180 degrees for all muscle groups. CONCLUSIONS: This research indicates the RH can serve as an effective exercise to target the paraspinal musculature. An increase in muscle activation correlates to an increase in force production and strength and, typically, a decrease in pain.

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