Exploring the link between acute symptom changes and repetitive head impacts in boxing sparring

OBJECTIVES: The acute dose-response relationship between head impact exposure and the development of concussion remains elusive. Previous research has suggested that individual-specific approaches and the cumulative effects of head impacts should be investigated. This study aimed to monitor acute changes in concussion-related symptoms resulting from boxing sparring, and assess how they relate to head impact exposure. DESIGN: Observational cohort study. METHODS: Seven competitive boxers participated in this exploratory study. Symptoms of concussion were captured via the SCAT5 symptom scale upon recruitment, immediately before (PRE), immediately after (POST), and 48 h (48H) after a sparring session. Head impact data were collected with instrumented mouthguards. Each session's mean, median, highest-magnitude impact, cumulative sum, and time-weighted exposure for several injury severity metrics were qualitatively analyzed with respect to acute changes in symptom score. RESULTS: Group-based analyses did not show any differences in symptom scores PRE/POST-sparring (median change in total symptom severity score [ΔTSSS]: -1, p = 0.85, r = 0.07). Symptom number and TSSS were significantly lower at 48H compared to PRE (median ΔTSSS: -1, p = 0.02, r = 0.55). Four of 16 sessions (25%) from three participants showed a ΔTSSS >5. There was no strong association between session-specific exposure and change in symptoms, but time-weighted exposure metrics showed a better alignment than other metrics. CONCLUSIONS: Symptom number and severity PRE/POST sparring changes were rare and subtle, and the link to head impact exposure is unclear. Our exploratory analyses support the concept of individual-specific approaches, as this allowed us to identify patterns emerging from a few athletes that were not visible in cohort-averaged summaries. Understanding the relationships between head impact exposure, individual pre-disposition, and signs and symptoms of concussion is essential to designing risk reduction strategies.