Infant Leg Motion🔗

The HBCD data release includes Infant Leg Motion Wearable Sensor data acquired during visits V02 and V03.

Release Data🔗

Motion/accelerometry data collected from wearable infant leg sensors include raw and processed sensor recordings:

hbcd/
└── rawdata/
    └── sub-[ID]/
        └── ses-[V0X]/
            └── motion/
                # Calibration files
                ├── *_task-{Left|Right}LegMovement_tracksys-imu_acq-calibration_motion.tsv   (+JSON)
                └── *_task-{Left|Right}LegMovement_tracksys-imu_acq-calibration_channels.tsv (+JSON)

                # 72-hr recordings
                ├── *_task-{Left|Right}LegMovement_tracksys-imu_acq-primary_motion.tsv   (+JSON)
                └── *_task-{Left|Right}LegMovement_tracksys-imu_acq-primary_channels.tsv (+JSON)

hbcd/
└── derivatives/
    └── hbcd_motion/
        └── sub-[ID]/
            └── ses-[V0X]/
                └── motion/
                    # Kinematics
                    ├── Kinematics/
                    │   └── sub-[ID]_ses-[V0X]_desc-kinematics_recording-{20|25}_motion.json

                    # Physical Activity (PA)
                    ├── PA/
                    │   ├── sub-[ID]_ses-[V0X]_leg-{left|right}_desc-{accelerationPA|jerkPA}_BOUTS.tsv
                    │   ├── sub-[ID]_ses-[V0X]_leg-{left|right}_desc-{accelerationPA|jerkPA}_LOG.txt
                    │   ├── sub-[ID]_ses-[V0X]_leg-{left|right}_desc-{accelerationPA|jerkPA}_RAW.tsv
                    │   └── sub-[ID]_ses-[V0X]_leg-{left|right}_desc-{accelerationPA|jerkPA}_SUMMARY.json

                    # Metadata & Outputs
                    ├── PARAMETERS.json
                    └── sub-[ID]_ses-[V0X]_leg-{left|right}_desc-calibrated_recording-20_motion.tsv

Data Acquisition🔗

Infant leg movement data collected by wearable sensors for HBCD captures information related to motor behavior, physical activity, sleep. Wearable sensors are placed on the child's right and left ankles by an HBCD Study team member during a visit. Sensor data (accelerometer and gyroscope) was collected continuously over 72 hours to estimate movement frequency, intensity, and sleep periods. Caregivers followed typical routines, removing sensors only for water exposure (e.g., baths) and replacing them afterward. Each sensor (Axivity AX6) was calibrated by recording 10 seconds on each of its six flat surfaces before data collection. Sensors recorded accelerometer (±16 g) and gyroscope (±2000 dps) data at 25 Hz, enabling estimates of sedentary, light, moderate-to-vigorous activity, and sleep. See Pini et al. 2024 for a full measure description.

Quality Control🔗

For the calibration files, the 72-hour sensor data files, and the survey data, a random selection of files were manually reviewed on a weekly basis. Raw calibration files were checked to verify the presence of sufficient data for each of the six axes. Seventy-two hour sensor data files were checked for presence of data, labeling of right and left leg, and sampling rate used. Surveys were checked to confirm presence of responses. Note that only a small percentage of total files were reviewed due to the procedure being manual.

Issues were generally rare for sensor data and most data were deemed to be present and accurately collected. Errors that did arise were corrected when possible (though this was typically not feasible). Common errors noted include inadequate or missing data (due to human error, technical issues, or a parent/legal guardian declining to participate in this aspect of the study), sensors being removed for extended periods during the 72-hour collection, and incorrect sampling rate.

References🔗