L.M. Whalen1, K.A. Pribanic2, & D.P. Heil1

1Movement Science/Human Performance Laboratory, Montana State University, Bozeman, MT

2Mystery Ranch LTD, Bozeman, MT

Standard loads carried by military ground troops on patrol can include a rifle, an operations kit, a loaded backpack, and an armored vest, such as the modular tactical vest (MTV) used in this study. As load mass increases, so does the potential for fatigue and injuries. Finding the most economical load carriage system may allow troops to perform their duties in the safest and most effective manner. PURPOSE: This study assessed the energetic and kinematic effects of supporting an MTV with a backpack-style hip belt during overground hiking. It was hypothesized that the energetics of overground hiking with an MTV would improve with the use of a hip belt. METHODS: Nine women and eight men (Mean±SD: 25±8 years) hiked a 586 m unpaved, outdoor path, carrying a dummy rifle, under three conditions: wearing no MTV (Control); wearing a 17.7 kg MTV (A condition); wearing an MTV with an attached 0.6 kg hip belt (AB condition). Subjects hiked under each condition at three speeds: 67.0 m/min; 80.4 m/min; 93.8 m/min, for a total of 9 trials. Data for stride rate (SR; steps/min), energy expenditure (oxygen uptake, VO2; ml/min), and heart rate (HR; BPM) were measured with accelerometers and a portable metabolic system, then summarized for each trial and analyzed using a multivariate repeated measures ANOVA and Sheffe’s post-hoc at the 0.05 alpha level. RESULTS: At all speeds, SR was always lowest for the Control condition and highest for the AB condition, though not significantly (P>0.05). VO2 and HR were higher for the AB condition than for the Control and A conditions at all speeds, though not significantly (P>0.05). CONCLUSION: The use of an MTV with a hip belt was unexpectedly associated with non-significant trends to increase VO2, HR and SR for all hiking speeds. While many subjects noted greater shoulder comfort when using the hip belt, it is speculated that the belt’s repositioning of the MTV mass necessitated greater balance control during overground hiking, which then caused the observed increases in VO2 and SR. Further research should focus on a similar measurement strategy with attention paid to the mass distribution on the MTV as well as the fit of the MTV with reference to gender and body size of the wearer.

Study funded by Mystery Ranch LTD (Bozeman, MT)

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