Kate Tarver*1 & Kaitlin Gallagherǂ1, 1University of Arkansas, Fayetteville, Arkansas

Prolonged standing induces low back pain (LBP) in at least 50% of study participants. It is hypothesized that people who develop LBP during standing have high gluteus medius co-activation; however, there is no research on how interventions, such as intermittent walking breaks, influence co-contraction. PURPOSE: Examine the effects of different walking speeds on gluteus medius co-contraction. METHODS: Three males and two females (21-25 years) have participated in this study. The exclusion criterion includes any previous low back or hip injury, surgery and an allergy to rubbing alcohol. Electromyography (EMG) of bilateral gluteus medius were recorded during a baseline standing trial (0 mph), and three randomly ordered walking trials at three different set speeds of 1, 2, and 3 mph. Each trial was 1-minute, with the last 30 seconds recorded. Co-activation was assessed on the EMG using a cross correlation index (CCI). A one-way repeated measure ANOVA with a within factor of walking speed was run on the gluteus medius CCI. A Tukey post hoc test will be run on any significant main effects. RESULTS: There was a significant main effect of walking speed on CCI (p<0.0001). When walking at 1 mph, the CCI was -0.72+/-0.07. This was significantly different from the 0 mph (0.58+/-0.19, p<0.0001), 2 mph (0.38+/-0.28; p=0.0019) and 3 mph (-0.37+/-0.20; p=0.0016) conditions. There was no significant difference between the 2 and 3 mph conditions (p=0.9993). CONCLUSION: Based on the CCI values, all walking speeds demonstrated a tendency towards reciprocal firing of the gluteus medius muscles. The 1 mph had a higher CCI, which could be because of the very distinct stance and swing phases of walking or the need to walk at a slower than desired pace. As the speed increased, reciprocal firing was still evident, but not to the extent seen at 1 mph. During constrained standing tasks, the gluteus medius muscles were co-contracting, denoted by a positive CCI. As a result, walking did cause reciprocal firing of the gluteus medius muscles, indicated by a negative CCI. Further research that combines these results with lumbar spine movement will help reveal potentially beneficial walking speeds for the reduction of prolonged standing induced LBP.

This study was funded through a University of Arkansas Honors College Research Grant.

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