Megan Sax van der Weyden, James Kearney, Joel Martin. George Mason University, Manassas, VA.

INTRODUCTION: Load carriage of equipment is an occupational requirement of Law Enforcement Officers (LEO). LEO have a high prevalence of lower back pain (LBP) and previous studies have reported lower ratings of exertion when LEOs wear a vest versus a belt. Loaded vests and belts have both been shown to alter gait kinematics with no clear support for either. The effects of LEO duty belts on muscular activity during walking, a common movement performed by LEO, has not been reported in the existing literature. The purpose of this study is to analyze the effect of the LEO duty belts and vests on muscular activity while walking. METHODS: Twenty-four participants volunteered for the study (m=13, f=11, age=24.5yrs±6.0, height=1.69m±0.09, mass=73.0kg±11.1). Surface electromyography (sEMG) sensors were placed bilaterally on rectus abdominus (RA), multifidus (MF), biceps femoris (BF), and rectus femoris (RF). Participants walked on a treadmill for 30s at 1.34 m/s and 1.5% incline wearing no belt, tactical belt (7.2kg), and tactical vest(7.2kg) in a randomized order. sEMG data was collected at 2000Hz and bandpass (10-450Hz) and notch (60Hz) filtered. Root mean squared sEMG data for each condition were normalized to the control. Friedman’s tests and post-hoc Wilcoxon signed ranks test with Bonferroni corrections were utilized. All analyses were conducted in the R environment with significance set at p<0.05. RESULTS: The belt resulted in significantly more muscular activity than the control condition in the left RF(W=38, z=-3.2, p=0.004, rg=0.653), right RF(W=49, z=-2.88, p=0.012, rg=0.589), and left MF (W=44, z=-3.03, p=0.007, rg=0.618). The vest resulted in significantly more muscular activity than the control condition in the left RF(W=25, z=-3.57, p=0.001, rg=0.729), right RF(W=66, z=-2.4, p=0.049, rg=0.490), left MF (W=64, z=-2.46, p=0.042, rg=0.502), and right MF(W=23, z=-3.63, p<0.001, rg=0.741). Belt and vest conditions were not significantly different from one another. CONCLUSION: The increased muscle activity in some, but not all muscles, indicates altered recruitment patterns compared to unloaded walking. The present findings are interesting considering the prevalence of LBP in LEO. Important to note, a limitation of the study was the short trial duration. Future studies should analyze longer experimental sessions to more accurately simulate shifts LEO typically work.

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