The association between at-home exercise digital metrics and ALS disease progression in lower limbs
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
Background
Clinical assessments of Amyotrophic Lateral Sclerosis (ALS) are typically collected infrequently in clinic visits and may not fully capture domain-specific functional decline in daily life. Digital Health Technologies (DHTs) can support remote monitoring, but passive free-living measures often require prolonged wear time and may be influenced by non-motor factors. This study evaluated whether short, standardized, at-home lower limb exercises recorded with ankle-worn accelerometers provide objective and interpretable measures of lower limb disease progression in ALS.
Methods
We analyzed data from 349 participants with ALS enrolled in the decentralized ALS Research Collaborative Study. Participants completed repeated self-entry ALS Functional Rating Scale-Revised (ALSFRS-RSE) assessments and wore bilateral ankle accelerometers during monitoring periods between September 2014 and January 2023. During each period, participants performed brief seated knee flexion-extension exercises at home. A previously developed signal processing pipeline was used to derive four exercise metrics: count, duration, intensity, and similarity. We examined baseline correlations with ALSFRS-RSE total and subdomain scores, longitudinal change using linear mixed-effects models, associations with gross motor item scores, differences by anatomical site of disease onset, and comparisons with free-living gait metrics.
Results
At baseline, exercise-derived metrics, particularly intensity and similarity, showed the strongest associations with the gross motor subdomain. Longitudinally, duration increased while intensity and similarity decreased, consistent with progressive slowing, reduced movement vigor, and reduced movement consistency (all p < 0.001); count did not change significantly. Worsening responses to gross motor items related to turning in bed, walking, and stair climbing were consistently associated with fewer, slower, less vigorous, and less consistent lower limb repetitions. Baseline intensity and similarity were lower in participants with lower limb disease onset on the corresponding side. Exercise-derived intensity showed model fit comparable to the strongest free-living gait metrics, while requiring substantially less observation time.
Conclusions
Short at-home lower limb exercises recorded using ankle-worn accelerometers provide scalable, objective, and interpretable measures of amyotrophic lateral sclerosis-related functional decline. Movement quality metrics, particularly intensity and similarity, may complement passive free-living monitoring and support remote digital clinical outcome assessment in ALS research.
Trial registration
NCT06885918.
