Effects of backpack chest straps on simulated shooting performance following repeated bouts of treadmill marching

Abstract

Soldiers must quickly take action when called upon and normally carry heavy loads in the process. One piece of equipment that is vital to carrying this load is a backpack. While load carriage and physical performance have been researched in the past, it is unknown if changing the location of the shoulder and chest straps will influence physiological measures or marksmanship performance. PURPOSE: The purpose of this study was to examine how changing the location of backpack shoulder straps affect physiological and marksmanship values during a simulated road march while under army assault load conditions. METHODS: Seven young healthy men (Mean + or - SD: 22 + or - 3.5 yrs; 24.75 + or - 1.38 kg/m 2 BMI) participated in this study. Subjects wore load carriage equipment (body armor 8.05 kg, backpack 21.7 kg, rifle 3.25 kg) during three separate testing periods. Each period consisted of 120 minutes of marching and 6 minutes of shooting with an airsoft rifle equipped with a laser-based shooting system. Each of the lab visits corresponded to testing one of three chest strap conditions: modified chest strap (MCS), standard chest strap (SCS) and no chest strap (NCS). Heart rate, upper limb oxygen saturation, discomfort, shot accuracy and shot score were analyzed using repeated measures ANOVA (alpha=.05). RESULTS: There were significant main effects of trial (p=0.018) and time (p=0.000) when examining discomfort. There was a significant main effect of trial (p=0.002) for upper limb oxygenation. There was also a significant trial (p=0.017) main effect for heart rate. There were no main effects for either shot score or shot accuracy. CONCLUSION: There were no significant differences in any marksmanship value. However, there were significant differences in heart rate, discomfort and upper limb oxygen saturation. This would suggest that the location of backpack shoulder straps may have an effect on physiological measures while having no effect on performance measures during a simulated road march.