A pilot study using actigraphy to examine activity performance and its relationship with activity capacity in adults with facioscapulohumeral muscular dystrophy

Background Weakness associated with facioscapulohumeral muscular dystrophy (FSHD) impacts daily activities. Impact is often measured using standardized clinical assessments, documenting activity capacity, and only captures a snapshot of function. Wearable sensors may enable assessments of real-world activity performance. Objective To examine activity performance (actigraphy) and its relationship with capacity (clinical measures of strength and function) in adults with FSHD. Methods Remote assessments were piloted in a subgroup from Motor Outcomes to Validate Evaluations in FSHD. Participants wore waist-worn activity monitors for 7 days. Activity metrics included moderate-to-vigorous intensity physical activity (MVPA), time in activity levels, and step counts. Descriptive statistics summarized activity, Mann Whitney U tests compared groups, and correlation analyses examined relationships between activity performance and capacity. Results Thirteen subjects wore the device for a median of 7 days. Most time was sedentary, with minimal vigorous activity. Participants spent a median of 23.1 min daily (IQR: 23.8) and 161.7 min weekly (IQR: 157.9) in MVPA. Median daily step count was 4245 (IQR: 2892), with a median maximum step count of 20 (IQR: 7) within a 10-second epoch. Correlations were found between total MVPA and 10mw/r (ρ=−0.720, p = 0.006) and TUG-comfortable (ρ=−0.720, p = 0.006), and between maximum step count and several functional measures. Conclusion This pilot study provides insights into activity performance and its relationship with capacity in a small cohort of adults with FSHD. Total MVPA and maximum step count appear most informative for evaluating activity performance; larger studies are needed to confirm findings and assess psychometric properties of these metrics.