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THE INFLUENCE OF ANKLE POSITION DURING A STRAIGHT-LEG RAISE ON THE PASSIVE RESISTIVE PROPERTIES OF THE POSTERIOR HIP AND THIGH MUSCLES

Abstract

Ty B. Palmer1, Kazuma Akehi1, Ryan M. Thiele1, Douglas B. Smith1, Aric J. Warren1, and Brennan J. Thompson2; 1Oklahoma State University, Stillwater, OK; 2Texas Tech University, Lubbock, TX

PURPOSE: To examine the influence of ankle position on passive torque (PT), range of motion (ROM), and electromyography (EMG) of the posterior hip and thigh muscles during a passive straight-leg raise (SLR) assessment. METHODS: Thirteen healthy participants (mean±SD age=23±2yr; mass=69±15kg; height=169±10cm) performed six randomly ordered passive SLR assessments involving two assessments at each condition, which included the ankle positioned in dorsiflexion (DF), plantar flexion (PF), and a neutral (NTRL) position. All SLRs were performed using an isokinetic dynamometer programmed in passive mode to move the foot toward the head at 5°·s-1. For each SLR, participants laid in a supine position, with the knee braced in full-extension and the ankle immobilized in either 10° of DF, 10° of PF, or a NTRL (0°) position using an adjustable, custom-built stabilizing apparatus. All assessments were conducted on the right leg, while the left thigh and ankle were secured with restraining straps. Bipolar surface EMG amplitude of the biceps femoris was sampled during each SLR and expressed as a percentage of the maximal EMG amplitude that was corrected for initial baseline noise. PT and EMG amplitude were determined at four common joint angles (θ) separated by 5° during the final common 15° ROM for each participant. RESULTS: Maximum ROM was lower for the DF than the NTRL (P=0.003) and PF (P<0.001) conditions. PT was greater for the DF than the NTRL and PF conditions at θ3 (P=0.001) and was greater for the DF than the NTRL condition at θ4 (P=0.003) but was not different between conditions at θ1 and θ2 (P>0.05) (Figure 1). PT also increased with joint angle for the DF, PF, and NTRL conditions (P<0.001). There were no joint angle or condition-related differences (P>0.05) for EMG. CONCLUSION: These findings suggest that the SLRs performed with the ankle positioned in DF elicited greater PT and lower ROM of the posterior hip and thigh muscles than the SLRs with the ankle positioned in PF or a NTRL position.

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