INTRODUCTION: Biathlon is an Olympic endurance sport that combines skating style cross-country skiing (~7.5-20 km) and rifle shooting (2-4 series of 5 shots), where ~30-53% of the final performance rank is determined by shooting performance (Luchsinger, 2017). Biathletes perform shooting training both in resting conditions and at exercise intensities ranging from low to high. This study examined the effect of exercise intensity on hit percentage and related technical variables in standing shooting during roller ski skating under ecological conditions. It was hypothesized that increasing exercise intensity would impair shooting performance, with rifle barrel velocity as a significant mediator. METHODS: Nineteen male biathletes performed two series of standing shooting in the following order of exercise intensity: rest, low (%heart rate max; blood lactate in mMol/L: 73 ± 4, 1.5 ± 0.3), moderate (84 ± 3; 2.4 ± 0.6), `race-pace` (90 ± 2; 4.5 ± 0.8) and `final-lap` (i.e., near-maximal effort) (93 ± 3; 8.7 ± 1.4). Except for rest, each shooting series was preceded by 1 km roller ski skating in a competition track. Qualisys motion capture and an accelerometer tracked movements of the rifle, body and trigger. Primary outcomes were number of hit/miss and total distance from center, with barrel velocity modelled as a mediator. In total, 940 shots were analyzed. Logistic regression and linear mixed models were used to analyze statistical effects of intensity (a = 0.05). RESULTS: Exercise intensity increased the likelihood of miss at `race` (odds ratio (OR): 2.2, 95%CI 1.0-4.7) and `final-lap` (OR: 2.8, 95%CI 1.4-5.8) intensities compared to rest, with no differences between rest, low and moderate intensities (p > 0.4). Distance from center (~32 ± 15 mm at rest, low, moderate, 36 ± 20 mm at `race` and 40 ± 23 mm at `final-lap`) was significantly affected by intensity (p < 0.001). We found strong significant mediator effects of barrel velocity (mean over the last 250 ms before trigger) on both hit/miss and distance from center. DISCUSSION/CONCLUSION: This study indicates that exercise intensity has a negative effect on standing shooting performance in biathlon which can mainly be explained by an increase in barrel velocity (standing still becomes problematic). Effects were mainly seen at the two highest (race like) intensities, indicating that considerable amounts of shooting practice might need to be performed at high, competition-like exercise intensities for specificity reasons.
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