Measurement Performance of Activity Measurements with Newer Generation of Apple Watch in Wheelchair Users with Spinal Cord Injury

Abstract

Background The level of physical activity (PA) of people with spinal cord injury (SCI) has an impact on long-term complications. Currently, PA is mostly assessed by interviews. Wearable activity trackers are promising tools to objectively measure PA under everyday conditions. The only off-the-shelf, wearable activity tracker with specific measures for wheelchair users is the Apple Watch. Objectives This study analyzes the measurement performance of Apple Watch Series 4 for wheelchair users and compares it with an earlier generation of the device. Methods Fifteen participants with subacute SCI during their first in-patient phase followed a test course using their wheelchair. The number of wheelchair pushes was counted manually by visual inspection and with the Apple Watch. Difference between the Apple Watch and the rater was analyzed with mean absolute percent error (MAPE) and a Bland–Altman plot. To compare the measurement error of Series 4 and an older generation of the device a t-test was calculated using data for Series 1 from a former study. Results The average of differences was 12.33 pushes (n = 15), whereas participants pushed the wheelchair 138.4 times on average (range 86–271 pushes). The range of difference and the Bland–Altman plot indicate an overestimation by Apple Watch. MAPE is 9.20% and the t-test, testing for an effect of Series 4 on the percentage of error compared with Series 1, was significant with p < 0.05. Conclusion Series 4 shows a significant improvement in measurement performance compared with Series 1. Series 4 can be considered as a promising data source to capture the number of wheelchair pushes on even grounds. Future research should analyze the long-term measurement performance during everyday conditions of Series 4.

Accuracy and Precision of Actigraphy and SMARTwheels for Measuring Push Counts Across a Series of Wheelchair Propulsion Trials in Non-disabled Young Adults

“…Overall, compared to manual counting, SW slightly undercounted total pushes (SD) averaged across 16 workloads (manual: 50 [8] pushes vs SW: 48 [8] pushes). We suspect the SW undercounting could stem from discrepancies of defining a "push" or due to a push occurring on the wheel and not the push rim where the sensor on the SW is located.…”

“…Conversely, compared to manual counting, both ActiGraph accelerometers overcounted total pushes (SD) averaged across all 16 workloads (upper arm: 54 [11] pushes, wrist: 63 [12] pushes, manual: 50 [8] pushes). Due to limited research in using wearable devices for wheelchair push counts, comparisons of our study population with existing research are limited.…”

“…7 SW devices are considered the gold standard but are not cost-effective and currently no longer in production (SW cost: $15,000 USD in 2012, ActiGraph Accelerometer cost: $430 USD, Apple Watch Series 8 cost: $399 USD, and Fitbit Flex 2 cost: $229 USD). There has been recent interest in the accuracy and/or precision of commercially available wearable devices such as Apple Watch [8][9][10][11] and Fitbit. 8 The Apple Watch Series 4 has demonstrated a mean absolute percentage error (MAPE) of 9.2-13.9% 8,9 compared with manual counting of pushes during wheelchair propulsion, and this was substantially better than the Fitbit Flex 2 (MAPE of 59.7%).…”

“…There has been recent interest in the accuracy and/or precision of commercially available wearable devices such as Apple Watch [8][9][10][11] and Fitbit. 8 The Apple Watch Series 4 has demonstrated a mean absolute percentage error (MAPE) of 9.2-13.9% 8,9 compared with manual counting of pushes during wheelchair propulsion, and this was substantially better than the Fitbit Flex 2 (MAPE of 59.7%). 8 To our knowledge, there are currently no data on the accuracy and/or precision of research-grade devices for push counts.…”

“WOT” Do We Know and Do About Physical Activity of Children and Adolescents With Disabilities? A SWOT-Oriented Synthesis of Para Report Cards

“…The Irish and Canadian teams reported a "lack of appropriate accelerometer data," which projects further challenges to collecting PA data accurately. It should be acknowledged in this regard that atypical gait as well as wheelchair use are still not accurately measured using off-the-shelf wearable smart devices (Benning et al, 2021). To fill this gap, the Canadian team challenged the policymakers to create "populationspecific guidelines" customized for CAWD (Arbour-Nicitopoulos et al, 2022).…”