Table 1.

CHAMP 2022 checklist of information to include when reporting laboratory validation studies of head acceleration measurement devices.

Checklist Item	Explanation	Example(s)	Reported on Page No
1. Sensor Technology and Specifications
(1a) Device model name	The name or model of device used to collect data	PMID: 33051745, “The Cue, GForceTracker, and Shockbox sensors were mounted directly inside the helmet.”	________
(1b) Sensor type	The type of sensor (e.g., triaxial linear accelerometer, triaxial ARS)	PMID: 26268586, “The X2 system has a 3-axis linear accelerometer and a 3-axis angular rate sensor…”	________
(1d) Sensor sample rate	The sampling rate of the sensor	PMID: 32975553, “The sensor records 62 ms of data at 1000 Hz….”	________
(1e) Sensor magnitude range	The range of magnitudes the sensor can record	PMID: 23604848, “Mouthguard sensing is accomplished via a triaxial accelerometer (ADXL377, Analog Devices, Inc., Norwood, MA, USA) with 200 g maximum per axis and a tri-axial angular rate gyroscope (L3G4200D, ST Microelectronics, Geneva, Switzerland) with 40 rad/s maximum per axis.”	________
(1f) If applicable, device hardware/firmware version number	The version number related to the hardware/firmware for the device	PMID: 29613824, “Hardware and firmware were fully up to date according to the manufacturers at the time of testing [xPatch: Hardware updated Oct 2014, Software and firmware updated Aug 2017; SIM-G: Hardware updated Jun 2014, Software and firmware updated Aug 2017]”	________
(1g) Recording trigger threshold	The sensing threshold (e.g., 10 g) for an event to be recorded on the head acceleration measurement device and how the trigger threshold is evaluated	PMID: 23891566, “The helmet recorded …if the impact exceeded 10 g.”	________
(1h) Pre-trigger duration	Duration of pre-trigger data recorded	PMID: 32975553, “…10 ms before and 52 ms after linear acceleration exceeds the threshold.”	________
(1i) Post-trigger duration	Duration of post-trigger data recorded	PMID: 32975553, “…10 ms before and 52 ms after linear acceleration exceeds the threshold.”	________
(1j) Device form factor and attachment	The type of device/how the device is mounted (e.g., mouthguard)	PMID: 30802147, “MV1 (MVTrak) is a sensor system designed for custom-molded placement in the left external ear canal to optimize coupling to the head.”	________
2. Surrogate Selection
(2a) Surrogate used	The surrogate used (e.g., non-biofidelic [by intent] test device, anthropometric test device (ATD), post-mortem human subjects (PMHS), human volunteers)	PMID: 23846161, “A Hybrid III (HIII) 50th percentile male ATD head and neck with the 3-2-2-2 accelerometer array was rigidly mounted at T1.”	________
(2b) Inertial properties of surrogate	Geometry and mass—including what reference population is intended to be represented by this surrogate	PMID: 27155744, “This ATD had the inertial properties of a 50th percentile male head.”	________
(2c) If applicable, modifications made to standard surrogates	Any modifications made to standard surrogates for this study	PMID: 34263384, “Modifications to the NOCSAE headform include a mouth cut-out for mounting dentitions and a Hybrid-III neck adapter to replace the standard rigid neck and allow 6DOF head motion.”	________
(2d) If applicable, corresponding neckform and/or other body segments used	The neckform used to simulate head-neck response (e.g., Hybrid III neck, THOR neck) and/or other body segments (e.g., torso) used to simulate the system mass	PMID: 21994068, “… mounted to a standard HIII neck was used to replicate the response of a football player’s head. Per manufacturer’s specification, the cable in the HIII neck was tensioned to 1.1 Nm (10 in·lb.).”	________
(2e) Modifications made to standard neckforms, if applicable	Any modifications made to standard neckforms for this particular study	PMID: 33000448, “…the lower neck mount of the Hybrid III dummy was modified to incorporate a spherical ball joint that allowed for lateral flexion and twist of the neck.”	________
(2f) Validation of the surrogate	Evidence that the surrogate has been shown to produce a validated response for the chosen application	PMID: 29613824, “These reference sensors have been found to exhibit high fidelity (ref) and were considered to quantify the true head kinematics of the headform during impact.”	________
(2g) Mounting of the device on the surrogate	Details on how the device is mounted on the surrogate and the biofidelity of that mounting	PMID: 29383374, “The dental model was rigidly attached to the ATD headform in the place of the upper dentition, and the instrumented mouthpiece was mounted on the dental model, with the lower jaw firmly clamped to the mouthguard simulating jaw clenching…”	________
(2h) Factors related to coupling of the device to the surrogate	Specific parameters that could influence coupling of the device to the surrogate (e.g., helmet fit, skin/hair surrogate, use of nylon skull cap, sweat, jaw mechanics)	PMID: 23891566, “The helmet was fit by inflating the Z-pad bladders until they contacted the head.”	________
3. Test Conditions
(3a) Test device	The device used in testing (linear impactor, pendulum, drop tower)	PMID: 21451177, “The helmet was impacted using a pneumatic linear impactor.”	________
(3b) Impactor surface and mass	The type and material of the impact interface (elastomer padding, use of anvils, etc.). Provide the mass and its relevance to desired test conditions	PMID: 24920257, “The impactor mass was 14 kg and was padded with a 36 mm thick, 127 mm diameter vinyl nitrile pad (Impax VN 600, Der-Tex Corp, Saco, ME) without the standard hard plastic cap. This configuration generated an impact amplitude and duration similar to that observed during helmet-to-helmet impacts.”	________
(3c) Surrogate orientation and mounting, if applicable	How the surrogate was placed in the test device	PMID: 24920257, “Both headforms were mounted on a 50th percentile male Hybrid III neck mounted to a table free to slide horizontally parallel to the impactor’s axis.”	________
(3d) Impact velocity	The velocities used in testing and their relevance to desired test conditions	PMID: 32989591, “Regarding the impact velocities used for the testing, three of the used velocities (5.5, 7.4, and 9.3 m/s) are based on the National Football League (NFL) helmet test protocol, and an additional lower velocity (3.6 m/s) was added to analyze impacts of lower intensity as well.”	________
(3e) Impact duration	The duration(s) used in testing and their relevance to desired test conditions	PMID: 29613824, “The helmeted tests yielded average impact durations of 10.7 (1.3) milliseconds. The padded impactor to bare head condition was performed with a vinyl-nitrile foam impactor face measuring 127 mm in diameter and 40 mm thick. These tests yielded average impact durations of 12.5 (1.3) milliseconds and were chosen to provide similar impacts to the helmeted condition without the effect of the helmet. The rigid impactor to bare head condition was performed with the same flat, rigid, nylon impactor face from the helmeted tests to be representative of impact magnitudes and durations seen in unhelmeted impacts. These impacts yielded average durations of 3.6 (0.25) milliseconds.”	________
(3f) Impact location	The impact location(s) used in testing and their relevance to desired test conditions	PMID: 29613824, “Impacts were performed to the front, front boss, rear boss, and rear locations of the headform at targeted linear acceleration magnitudes of 25, 50, 75, and 100 g. Impact locations were equally spaced around the head and chosen because of their variability in direction of force.”	________
(3g) Impact direction	The direction(s) of impact used in testing and their relevance to desired test conditions	PMID: 26268586, “Ten impacts were nominally centroidal, i.e., the impactor’s axis passed near a vertical axis through the headform’s COG.” PMID: 26268586, “The front-oblique test condition was intended to represent a centric impact (head CG path eccentricity = 65 mm) and the rear eccentric test condition was intended as a more eccentric impact (head CG path eccentricity = 101 mm).”	________
(3h) Number of trials	The number of trials performed for each of the test conditions	PMID: 17597937, “Three drops were performed at each location.”	________
(3i) If applicable, helmet manufacturer/model name	The name of the manufacturer/model of the helmet used in impact testing	PMID: 29613824, A large Riddell Speed (Riddell, Elyria, OH) football helmet without the facemask was worn by the headform throughout helmeted tests	________
(3j) Repeatability and reproducibility of test conditions	Methods used to evaluate the repeatability and reproducibility of the test conditions and surrogate	PMID: 24920257, “Repeatability was assessed using the COV, which equals the ratio of the standard deviation (SD) to the mean, expressed as a percentage. Repeatability was categorized as excellent (COV ≤ 3%), acceptable (3 < COV ≤ 7%), marginal (7 < COV ≤ 10%) and poor (COV > 10%). The COVs for PLA and PAA were calculated for each series of five repeated tests for all eight impact conditions in each lab.”	________
4. Reference Sensor Measurement
(4a) Reference sensor type and model	The type of sensor or measurement device used as a reference (triaxial accelerometer, nine-accelerometer package, high-speed video), including the sensor part number	PMID: 26268586, “…a 3-2-2-2 array of linear accelerometers (Endevco 7264B-2000 g, San Juan Capistrano, CA)”	________
(4b) Reference sensor mounting	The method and location for reference sensor mounting	PMID: 26268586, “…a 3-2-2-2 array of linear accelerometers (Endevco 7264B-2000 g, San Juan Capistrano, CA) installed in a compact cluster (rx = ry = 34 mm, rz = 27 mm) in a modified load-sensing headform (MLSH) based on the 50th percentile male Hybrid III headform.”	________
(4c) Reference sensor sampling rate	The sampling rate of the reference sensor	PMID: 26268586, “…modified load-sensing headform (MLSH) based on the 50th percentile male Hybrid III headform. Accelerometer data were acquired at 10 kHz with hardware anti-aliasing filters prior to digitization (SAE Channel Class 1000).”	________
(4d) Reference sensor magnitude range	The range of magnitudes the reference sensor can record		________
(4e) Reference sensor filtering	Filtering methods used for the reference measurements	PMID: 29613824, “The reference data were filtered at CFC 1000 for linear acceleration and CFC 155 for rotational velocity.”	________
(4f) Time synching of reference sensor to head kinematic device	Method for synching reference data to wearable device data	PMID: 31297724, “Mouthpiece and reference traces were time-aligned such that the first data point that crossed the 5 g trigger threshold was set to time t = 0.”	________
5. Advanced Post-processing
(5a) Data transformation	Methods used to transform recorded data to analyzable data (e.g., numerical integration from angular velocity to angular acceleration, transformation from the location of the sensor to the center of gravity of the head, if transformation used, specify measurements defining the location to which data is transformed, must disclose if a “black box” algorithm was used)	PMID: 31122140, “The acceleration data are transformed to calculate linear acceleration at the centre of gravity of the head. Rotational acceleration is calculated from rotational velocity using five-point differentiation. Both the transformation and differentiation were carried using the software supplied by X2Biosystems.” PMID: 34263384, “Kinematics measured by the mouthpiece were transformed to a local head coordinate system using a rigid body transformation based on the geometry of each headform. Detailed 3D surface scans of both headforms with the IM affixed to the upper dentition were obtained to determine the location and orientation of the sensing elements in relation to the head CG (Artec Eva, Artec 3D, Santa Clara, CA). Reference measurements at the maxilla and device measurements from the electronics board inside the head of the MLSH were transformed to the head CG based on detailed computer drawings”	________
(5b) Kinematic data filtering	Any filtering used for processing data collected from a wearable device; must disclose if manufacturer “black box” post-processing was used. Include offset removal	PMID: 29383374, “Raw signals were low-pass filtered according to Society of Automotive Engineers protocols. The mouthpiece data used threshold frequencies of 300 Hz and 110 Hz for linear acceleration and angular velocity, respectively, with 110 Hz being the bandwidth limit for the gyroscope.” PMID: 30802147, “Raw data are uploaded to the MVTrak server before being processed by the producer’s algorithm.”	________
(5c) Other post-processing techniques	Any software or hardware used for processing data collected from a wearable device (e.g., impact detection filtering, infrared system); must disclose if manufacturer “black box” post-processing was used. Provide details on validation of post-processing techniques (e.g., training data set used)	10.1177/1754337117739458, “…data were processed using proprietary algorithms from which the resultant peak linear acceleration (PLA) and peak angular acceleration (PAA) impact magnitude measures were output.”	________
(5d) Event removal	Clear, objective methods for sensor event removal, if any sensor events are removed from analysis	PMID: 32975553, “A positive single axis maximum of 28.9 rad/s and negative single axis absolute maximum of 29.1 rad/s were determined. One trial was removed from analysis because this maximum angular velocity measurement was sustained for more than five consecutive data points.”	________
6. Analytical Methods and Data Reporting
(6a) Validation metrics, including equations used to derive metrics, if applicable	Description of each primary and secondary validation metric (e.g., impact counts, peak linear acceleration, change in angular velocity)	PMID: 32975553, “Key event characteristics include peak angular velocity (i.e., maximum velocity during event), rise time (i.e., time for angular velocity to reach peak velocity from event start at velocity surpassing 5% of peak), fall time (i.e., time from peak velocity to 5% of the peak), and a proxy for average angular acceleration (i.e., approximated by taking the ratio of peak angular velocity and the rise time).”	________
(6b) Statistical and analytical methods for comparison	The statistical and analytical methods used to compare the wearable device data to the reference measures (e.g., recall, RMS error, general linear mixed models)	PMID: 31297724, “Average resultant peak percent error was used to determine agreement between reference data and the mouthpiece data. Normalized root-mean-square error (NRMS) was used to determine agreement over the entire impact duration recorded by the mouthpiece (60 ms).”	________