INTRODUCTION: Skiing while carrying the additional mass of a rifle has detrimental effects on both physiologic and biomechanical measures of skiing performance [1,2]. However, it may be possible to offset these detrimental impacts by manipulating the position of the rifle on the athlete`s back or the tightness of the harness. While this has been considered in theoretical studies [3], to date it has not been investigated experimentally. Therefore, the primary purpose of this study was to evaluate the impact of changing rifle position and harness tightness on physiologic response during skiing in elite biathletes. Secondarily, we also examined whether harness position and tightness influences shooting timing. METHODS: Eight members of the US Biathlon National Team participated in this study. On day one athletes performed an incremental step test to determine maximal oxygen consumption (VO2 max). On day two athletes skied three-minute intervals wearing their rifle in their habitual harness position (HAB), followed, in a randomized order, by combinations of rifle high or low on their back and harness tight or loose (HL, HT, LT, LL). Oxygen consumption (VO2) was averaged over the last minute of each interval and used to calculate gross efficiency (GE) and economy (E). Tidal volume (VT) and minute ventilation (VE) were also calculated to examine effects of harness on breathing patterns. Following each interval athletes performed a dryfire shooting bout in standing position which was recorded by highspeed video to assess how harness position influenced time to get into and out of shooting position. Linear mixed effects models with Bonferroni corrected pairwise comparisons were used to assess effect of harness condition. RESULTS/DISCUSSION: There were significant fixed effects of condition for VO2 (p = 0.026), GE (p = .003), and E (p = .007). Pairwise comparisons showed that VO2 was lower (p = .045) while both GE (p = .001) and E (p = .004) were higher in the HT condition than HAB condition. The HT condition may move the center of mass of the athlete-rifle system into a more advantageous forward lean position, thus increasing skiing efficiency. There were no significant fixed effects of condition for any of the other variables (all p > .05) suggesting that moving and especially tightening the harness did not impact breathing while skiing or ability to get into and out of shooting position quickly. CONCLUSION: Athletes may be able to offset the negative impacts of the weight of the rifle by manipulating the position of the rifle on their back and/or the tightness of the harness.
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