Sex And Position Differences In Head Impact Kinematics Over The Course Of A Bobsled World Cup: A Pilot Study

Abstract

PURPOSE: To determine if there are differences in average workload, peak linear acceleration (PLA, g), peak linear velocity (PLV, m/s) between positions and sex during the 2021 - 2022 World Cup Tour. METHODS: Twelve elite bobsled athletes (6 Females; 3 pilots, 9 push athletes; 30 ± 5 y; F 173 ± 8 cm, 75 ± 5 kg; M 183 ± 5 cm, 101 ± 5 kg) wore an accelerometer-enabled mouthguard during all training sessions and competitions occurring over ten consecutive weeks to quantify head impact kinematics. The number of impacts, PLA, and PLV, and workload (J) were calculated from the raw accelerometer waveforms. A head impact was defined as an instant where PLA exceeded 8 g. Summary data, including number of days and runs captured, and number of head impacts were determined. Average values for each metric were determined. Two separate generalized linear mixed models via PQL were used by using a fixed effect of sex or position and random effects of run number, training or competition session, athlete. An effect was considered significant if p < 0.05. RESULTS: 48 training days and 53 competition days were recorded, with a mean of 2 (range, 1 - 3) runs per day. A total of 1900 head impacts were recorded over the season with a mean of 11 ± 8 impacts recorded per run. Mean head impacts per run were similar between males (11 ± 8) and females (11 ± 8, p = 0.96) as well as between position (pilots, 11 ± 6; push, 10 ± 11.; p = 0.27). PLA (F, 11.9 ± 3.5 g; M, 12.4 ± 3.9 g; β = 0.05, p = 0.96), PLV (F, 1.1 ± 0.3 m/s; M, 1.1 ± 0.3 m/s; β = 0.05, p = 0.41), and workload (F, 3.0 ± 1.9 J; M, 3.3 ± 2.2 J; β = 0.08, p = 0.49) were similar between males and females. Push athletes experienced significantly higher workload than pilots (pilot, 2.9 ± 2.0 J; push, 3.9 ± 2.2 J; β = -0.19, p = 0.04). PLA (pilot, 12.5 ± 3.9 g; push, 11.5 ± 3.4 g; β = 0.09, p = 0.07) and PLV (pilot, 1.0 ± 0.3 m/s; push, 1.2 ± 0.3 m/s; β = -0.10, p = 0.07) did not reach the threshold for significant difference. CONCLUSION: Cumulative workload was greater in push athletes compared to pilots throughout a bobsled World Cup season. This work provides a foundational understanding of the repetitive head impacts that occur in bobsled athletes. Future work should determine the effects of repetitive head impacts on neurocognitive function to determine methods to optimize acute and long-term health outcomes among bobsled athletes.