Table 3.

Logistical requirements and activity characteristics when collecting head acceleration data in sporting and military environments.

Logistical requirement	Activity characteristic	Comment
Battery life	Competition, practice, or training event period	Many sports have competition durations between 40 and 90 min. In some sports, e.g., cricket, an athlete may be active for many hours. Practice sessions vary in length as well. Military training applications may span many hours, often resulting in distribution of multiple sensors per day if battery life is insufficient
	Size of field	If the device has continuous transmission from device to base station, field size may require higher powered transmitters.
	Number of sessions per charge	Often data collection plans involve a single session in a 24-h period allowing time for battery recharge. However, some data collection structures involve multiple sessions in a 24-h period. Multiple devices per day may be needed if battery life is insufficient
Memory	Number of HAEs	Per person these may range from one every few hours in projectile sports (e.g., baseball) to potentially several per minute, depending on the trigger threshold for sampling an impact and false event recordings. The device should be configured to capture HAEs for the duration of the activity of interest.
Form factor and attachment	Activity considerations (e.g., protective equipment commonly used, communication requirements, duration of wear, etc.)	Helmet, mouthguard, or external cranium are common points of attachment. If able, consider the best attachment point for a given activity. Adding a small mass to a helmet or mouthguard may be more acceptable to the athlete than attaching a device to the head. Communication among athletes in the sport (e.g. soccer) may influence compliance of the participant if the device interferes with speech. Device comfort may influence the compliance if the sensor system is intrusive or uncomfortable. This may be exacerbated for long duration of wear
Data transmission	Number of participants/athletes	If the objective of measuring HAEs in real-time (e.g. monitoring of high-risk events), then ideally data will be transmitted to the sideline and monitored. If the objective is to passively monitor HAEs for evaluation after the session or season or if real-time monitoring is not feasible, then extracting data after a session is reasonable. A large number of study participants typically leads to longer time frames needed to extract data locally. Ideally, data will automatically be wirelessly transmitted to a centrally located storage unit
	Access to participants/athletes	Often strict schedules of participants limit the availability of individuals to be outfitted with sensors. Working around these schedules is often required in studies that require more time with the participant
	Concussion rules	Theoretically, participants could be removed from the session based on biomechanical head acceleration parameters in the absence of concussion signs and symptoms. Concussion rules may develop in tandem with sensor technology. However, at this time, this practice is not recommended given the lack of a specific biomechanical threshold for concussion