We developed a wearable sensor algorithm to determine the number of arm movement bouts an infant produces across a full day in the natural environment. Full-day infant arm movement was recorded from 33 infants (22 infants with typical development and 11 infants at risk of atypical development) across multiple days and months by placing wearable sensors on each wrist. Twenty second sections of synchronized video data were used to compare the algorithm against visual observation as the gold standard for counting the number of arm movement bouts. Overall, the algorithm counted 173 bouts and the observer identified 180, resulting in a sensitivity of 90%. For each bout produced across the day, we then calculated the following kinematic characteristics: duration, average and peak acceleration, average and peak angular velocity, and type of movement (one arm only, both arms for some portion of the bout, or both arms for the entire bout). As the first step toward developing norms, we present average values of full-day arm movement kinematic characteristics across the first months of infancy for infants with typical development. Identifying and quantifying infant arm movement characteristics produced across a full day has potential application in early identification of developmental delays and the provision of early intervention therapies to support optimal infant development.

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Background Characteristics of movement can differentiate infants with typical development and infants with or at risk of developmental disabilities. We used wearable sensors to measure infants’ typical movement patterns in the natural environment. Objective Our objectives were to determine (1) how many days were sufficient to represent an infant's typical daily performance, and (2) if there was a difference in performance between weekdays and weekend days. Design This was a prospective, observational study. Methods We used wearable sensors to collect 7 consecutive days of data for leg movement activity, from 10 infants with typical development (1–5 months old). We identified each leg movement, and its average acceleration, peak acceleration, and duration. Bland-Altman plots were used to compare the standard (average of 7 days) with 6 options (1 day, the average of days 1 and 2, through the average of days 1 through 6). Additionally, the average of the first 2 weekdays was compared with the average of 2 weekend days. Results The absolute difference between the average of the first 2 days and the standards fell below 10% of the standards (movement rate = 8.5%; duration = 3.7%; average acceleration = 2.8%; peak acceleration = 3.8%, respectively). The mean absolute difference between weekdays and weekends for leg movement rate, duration, average acceleration, and peak acceleration was 11.6%, 3.7%, 7.2%, and 7.3% of the corresponding standard. Limitations The small sample size and age range limit extrapolation of the results. Conclusions Our results suggest the best option is to collect data for 2 consecutive days and that movement did not differ between weekdays and weekend days. Our results will inform the clinical measurement of full-day infant leg movement for neuromotor assessment and outcome purposes.

Background: Advances in wearable sensor technology now allow us to quantify the number, type and kinematic characteristics of bouts of infant arm movement made across a full day in the natural environment. Our aim here was to determine whether the amount and kinematic characteristics of arm movements made across the day in the natural environment were related to developmental status in infants with typical development as they learned to reach for objects using their arms. Methods: We used wearable sensors to measure arm movement across days and months as infants developed arm reaching skills. In total, 22 infants with typical development participated, aged between 38 and 203 days. Of the participants, 2 infants were measured once and the other 20 infants were measured once per month for 3 to 6 visits. The Bayley Scales of Infant Development was used to measure developmental level. Results: Our main findings were: 1) infant arm movement characteristics as measured by full-day wearable sensor data were related to Bayley motor, cognitive and language scores, indicating a relationship between daily movement characteristics and developmental status; 2) infants who moved more had larger increases in language and cognitive scores across visits; and 3) larger changes in movement characteristics across visits were related to higher motor scores. Conclusions: This was a preliminary, exploratory, small study of the potential importance of infant arm movement characteristics as measured by full-day wearable sensor data. Our results support full-day arm movement activity as an area of interest for future study as a biomarker of neurodevelopmental status and as a target for early intervention.

Purpose: To investigate differences in the patterns of supine spontaneous leg movements produced before sitting onset between infants with typical development (TD) and infants at risk for developmental delay (AR). Method: Cross-sectional, observational study. Thirty-five infants were included, 18 infants with TD (130.4 ±38.0 days) and 17 infants AR (124.1± 65.7 days). Infants were placed in the supine position and video taped for 4 to 5 minutes while in an alert, content state. After the recording, videos were coded frame by frame to identify the type of each leg movement produced: single flexion, single extension, alternate flexion, alternate extension, parallel flexion, parallel extension, leg wave, leg circle, leg thump, foot rub, foot flexion, or foot rotation. Results: Unilateral movements (single flexion and single extension) were the most common leg movements in TD group. Infants AR produced a significantly lower proportion of unilateral and foot rub movements than infants with TD. Conclusion: These results provide a foundation of the types of leg movement pattern differences to build on in future research. Knowledge about differences in spontaneous movement patterns between infants AR and infants with TD has relevance both for early identification of neuromotor impairment and clinical practice.