Short prescribed exercises can quantify upper limb functioning in neurodegenerative disease

Digital health technologies (DHTs) can quantify movements in daily routines but rely heavily on participant adherence over prolonged wear times. Here we analyze accelerometry data from wrist-worn devices during short episodes of prescribed exercises (PEs) performed by 329 individuals living with amyotrophic lateral sclerosis (ALS) in a longitudinal study. We developed an automated and interpretable signal processing method to estimate upper limb movement counts, duration, intensity, and similarity of repetitions during PEs. Upper limb swing duration increased while intensity and similarity of movement decreased over time, indicating longer but less vigorous and less consistent upper limb movements over time. Intensity emerged as the most robust predictor of changes in upper limb function. The results suggest that PEs can effectively quantify upper limb function comparable to certain free-living measurements, providing greater flexibility in the clinical application of DHTs.