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.