INTRODUCTION: Biathlon is an Olympic endurance sport that combines cross-country skiing with precision rifle shooting. Biathlon performance has usually been analyzed in terms of skiing time, shooting accuracy, and time spent shooting, while limited investigation was conducted on the race physiological demands1,2. This study investigates exercise intensity distribution (EID) in different heart rate zones (Z1-Z5) across the laps of a summer biathlon sprint race, and whether EID affects the subsequent shooting performance. METHODS: This study involved 17 high to world-level Italian biathletes (6 females and 11 males) competing in a national summer biathlon sprint race. Each athlete wore a heart rate monitor during the race. The individualized 5 heart rate intensity zones were established by analyzing each athlete's lactate curve, previously determined through a roller skies laboratory test. Shooting performance was evaluated as the number of targets hit during the race, shooting time and time to first shot. Thereafter, athletes were divided into 2 groups based on whether they spent less or more than 50% of the lap time in Z5 (group 1 and group 2 respectively). The Friedman test, followed by pairwise comparisons with Wilcoxon test was used to evaluate EID. Mann-Whitney U test compared EID for male and females and shooting performance between group 1 and group 2. RESULTS/DISCUSSION: In the first lap of the race, the time spent in intensity zones Z3, Z4, and Z5 was similar (all p > 0,05). In the second lap, the time spent in Z5 began to increase accompanied by a decrease of time in Z3, leading to a distinct separation of the three zones in the third lap (all p < 0.001). Throughout the three laps, the percentage of time spent in Z4 remained relatively constant. There were no gender differences in EID in all the laps. (p > 0,05) Regarding shooting performance, there were no significant differences in shooting time and time to first shot for both the first and the second lap between group 1 and 2 (p > 0,05). The number of hit targets in prone shooting (after the first lap) did not differ between the two groups. Interestingly, in the standing shooting (after the second lap) a higher number of missed targets was found in the group that spend more than 50% of time in Z5 (p < 0.05). CONCLUSION: The study showed that the percentage of race time spent in Z4 remained stable, with a decrease in Z3 coinciding with an increase in Z5 across laps. Additionally, variations in time spent in Z5 seems to influence the standing shooting performance. However, further research involving multiple competitions and a greater number of athletes is important to support these findings. For the first time we analized the effect of EID on shooting performance during a race; our results have important practical implications that coaches should take into account when planning physical and shooting training for biathletes or when working on pacing strategies.
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