Validation of HeadCount-2w for estimation of two-week heading: Comparison to daily reporting in adult amateur player

Objectives: To validate the HeadCount-2w questionnaire for estimation of 2-week soccer heading by comparison to daily electronic diary reporting over the same two-week period. Design: Prospective observational study. Methods: Adult amateur soccer players completed HeadCount-daily, comprising 14 daily at-home assessments of soccer play and heading via a tablet PC. Following the 14 day period, players completed HeadCount-2w, a web-based two-week-recall questionnaire on soccer and heading. intraclass correlation coefficient (ICC) was estimated between HeadCount-daily, the reference standard, and HeadCount-2w estimates of heading during the same 2-week period. Results: 53 participants (38 men) reported a mean of 24.36 (median = 11.76) headers during 2 weeks via HeadCount-daily and a mean of 38.34 (median = 15.0) headers for the same 2 weeks via HeadCount-2w. The ICC comparing 2-week heading from HeadCount-daily and HeadCount-2w was 0.85. Linear regression of the log-transformed Headcount-daily on HeadCount-2w data yielded a slope of 0.71 (p < 0.001; 95% CI 0.54–0.82), suggesting that heading tends to be over-estimated by HeadCount-2w relative to HeadCount-daily. Slope estimates for men (0.65) and women (0.71) were similar. Conclusions: HeadCount, a self-administered web-based survey, is valid for self-reporting 2-week heading in adult amateur players, supporting its use in future research and as a simple and low-cost technique for exposure monitoring.