The Associations of Wet Bulb Globe Temperature With Match Injury and Concussion Incidence in American Youth Soccer
Brandon R. Merfeld, Kristín Haraldsdóttir, John Kohler, Jennifer L. Sanfilippo, Scott A. Anderson, Gabriella Lues et al. · Sports Health A Multidisciplinary Approach · 2026
Background: The relationship between heat stress and injury risk in youth athletes is unknown. The
Purpose: of the study was to identify the association between wet bulb globe temperature (WBGT) and injury risk in youth soccer athletes. Hypothesis: Overall injury incidence would increase, and concussion incidence would decrease with higher WBGT.
Study design: Prospective cohort study. Level of Evidence: Level 2.
Methods: Injury characteristics were recorded by athletic trainers at Elite Clubs National League youth soccer events throughout the United States over 2 years, and WBGT was calculated for each day of each event. The associations of nontime-loss and time-loss injury and concussion incidence with WBGT were assessed through separate negative binomial regression models, adjusted for age and sex.
Results: A total of 1584 injuries and 306 concussions were reported from 42 events representing 315,113 player-hours. Injury incidence was 5.0 per 1000 player-hours overall and higher for girls than boys (5.6 vs 4.4 per 1000 player-hours respectively, incidence rate ratio [IRR], 1.38; 95% CI, 1.1-1.7; P ≤ 0.001). Concussion incidence was 0.97 per 1000 player-hours, and girls had a higher concussion incidence than boys (1.20 vs 0.78 per 1000 player hours; IRR, 1.39; 95% CI. 1.0-1.9; P = 0.03). Higher WBGT was associated with a lower incidence of injuries overall (IRR, 0.986; 95% CI, 0.98-0.99; P < 0.01), time-loss injuries (IRR, 0.983; 95% CI, 0.97-0.99; P < 0.01), and concussions (IRR, 0.981; 95% CI, 0.97-0.99; P = 0.01), but not nontime-loss injuries (IRR, 1.00; 95% CI, 0.99-0.99; P = 0.86).
Conclusion: In this study of match injuries in youth soccer, we found that a higher WBGT was associated with a decreased incidence in overall injuries, as well as a lower incidence of concussions and time-loss injuries. Further research is warranted to understand the mechanisms behind these relationships, and whether they exist similarly in other athletic populations. Clinical Relevance: These
results help advance our understanding of environmental injury risk factors in youth soccer to inform decision making by support staff.