Background There is a growing range of wearable non-helmet mounted devices on the market and/or in use that purport to measure head impact responses. There is potential for these devices to be useful tools in research and injury management programs.

Objective Describe methods for assessing the validity of wearable head impact response devices.

Design Laboratory and qualitative observational methods. Tests on an exemplar wearable head impact response measurement “device” were undertaken in a laboratory using an instrumented Hybrid III head and neck and linear impactor. Football players in competitive matches wore the device and games were videoed. A qualitative protocol was applied to correlated device head impact events were those observed on video to examine sensitivity and specificity.

Setting Contact sport.

Participants Community level Australian football players.

Interventions None.

Main Outcome Measurements Head impact responses in vitro (linear and angular accelerations) and vivo (observed head impact characteristics).

Results Laboratory head impacts were performed at a number of impact sites and velocities. Laboratory tests identified significant correlations (p<0.05) between in-headform measured peak resultant linear and resultant angular accelerations and HIC with the device measured parameters. However, the device estimates of HIC were incorrect by a factor of 2 and angular acceleration by a factor of 0.7. Linear acceleration measurement was more accurate, but lacked precision. Qualitative video analysis showed approximately 60% correlation of device measured >30 g in game head impact events with observed head impacts, but in 18% events were not correlated with any head impact, and there were other errors.

Conclusions A combination of laboratory and field tests are critical in establishing the validity of wearable head impact response devices and should be performed as the first stage of research with these devices.