CDE Detailed Report

Resolution of time-synchronization is the amount of error allowed between the device timestamp and video timestamp. Appropriate answers for this would be ±1second, ±1millisecond, etc. The resolution will depend on the accuracy of the device clock and the accuracy of the video clock (e.g., if the device timestamp is accurate to the millisecond, and the video timestamp is accurate to the second the resolution would be ±1second). Please indicate time resolution of time-synchronization between the video and the device. For example, if both video and device has 1 second resolution for their real-time stamps, the time resolution would be 1 second.

Both video and device indicate an exposure(s)- happened within the allowable time-period (Maximum Allowable DeltaT). Head impact events in which both the video and the device indicate an exposure. Through careful review of the video, identify head impact exposures. The definition of this will vary by the sport setting studied but could include identifiable change in the head kinematics (in the case of a head impact in football for example) or an identifiable change in the ball trajectory (in the case of a head to soccer ball impact). It is highly suggested that this process be conducting by multiple coders blinded to each other's' efforts. Have a master coder reconcile any differences in exposure identification. Count the number of head impact events recorded on the device that can be confirmed via video. This may be tied to g-force level (e.g., impact as 25g+).

Please indicate manufacturer of video camera(s) used for recording event footage.

Data is best described when video and data correspond (option 3). The accelerometry device and video recording can independently capture exposure information and can be cross-verified to increase confidence of the exposure measurement. This CDE differentiates which set of information serves as the ground truth for verification. For example, if video is served as ground truth, exposures captured on video but not measured by the device would be considered as missing (false negatives). It is also an option to only consider exposures measured by both the video and the device to be 'verified' exposures. Please select from following options or, if another method is used, provide a detailed description of the method.

Head impact exposures observed on video but lacking corresponding device exposure data within the allowable time-period (Maximum Allowable DeltaT). Through careful review of the video, identify head impact exposures. The definition of this will vary by the sport setting studied but could include identifiable change in the head kinematics (in the case of a head impact in football for example) or an identifiable change in the ball trajectory (in the case of a head to soccer ball impact). It is highly suggested that this process be conducting by multiple coders blinded to each other's' efforts. Have a master coder reconcile any differences in exposure identification. Count the number of head impact exposures identified on video that do not have any corresponding data on the device within the allowable time-period.

The number of visually verified head impact events that resulted from head to head contact (including helmet to helmet contact).

The number of visually verified head impact events that resulted from head to body contact (e.g., head contacts the torso of another person).

The number of visually verified head impact events that resulted from head to ground contact (e.g., while falling or diving, head contacts playing surface).

Please indicate method of creating timestamps on video footage. The approach used to generate a timestamp for each individual video frame used to verify impacts. The timestamp is the time of day of a given video frame which will be compared with the time of day an event is recorded via the device. The timestamp can be generated by the camera using an internal clock (e.g., a GPS synched clock, an internal software clock, etc.) or can be tracked using an external source (e.g., a digital clock in view of the camera, calibrating the frames using a digital clock shown a single time, etc.). These methods are not exclusive, and other approaches may be described.

When date/time data are prepared for aggregation or sharing they should be converted to the format specified by ISO 8601, YYYY-MM-DDThh:mm:ss.

The number of visually verified events in which the person's body comes in contact with another person, the ground, or an object that result in an "acceleration event" of the head – without direct contact to the head.

Data is best described when video and data correspond (option 3). The accelerometry device and video recording can independently capture exposure information and can be cross-verified to increase confidence of the exposure measurement. This CDE differentiates which set of information serves as the ground truth for verification. For example, if video is served as ground truth, exposures captured on video but not measured by the device would be considered as missing (false negatives). It is also an option to only consider exposures measured by both the video and the device to be 'verified' exposures. Please select from following options or, if another method is used, provide a detailed description of the method.

Please indicate all activities under study which pertain to the subject (e.g. football, soccer). Associated CDEs are C56787, C56855, and C56826.