Background: Measures of strength and functional abilities may serve as important endpoints for FSHD clinical trials.
Objective: To examine the relationship of strength to functional assessments and document the 12 month change in measures of overall strength.
Methods: Individuals with FSHD participating in the ReSolve Study (NCT03458832) underwent measures of strength and function. Strength assessments included manual muscle testing (MMT) of 16 bilateral muscle groups and quantitative muscle testing (QMT) of 7 bilateral muscle groups. Functional assessments were performed including don/doffing a coat, Timed Up and Go, 10 meter walk/run, gait speed, ascending and descending 4 stairs, and the 6 Minute Walk Test.
Results: 240 participants (55% male) with a mean age of 50.5 (range 19-75) years completed baseline assessments across 11 international sites. 157 participants completed the 12 month visit. Participants presented with a mean strength of 4.1 (range=2.0-5.0) on the modified MRC scale, -5.2 (range -22-1) standardized QMT score. Overall lower extremity strength was correlated to functional assessments with the ? ranging from -0.68 to -0.83 (MMT). The 10 meter walk/run had the strongest correlation with strength. The correlation between individual lower extremity muscle groups and the 10 meter walk/run ranged from -0.43 to -0.72; with the hip extensors and knee flexors having the strongest correlations. Donning/doffing a coat was significantly correlated with overall upper extremity strength (MMT; ?= -0.60, p<0.0001). Significant strength changes were noted over 12 months in the overall MMT score (mean change -0.08; 95% confidence interval [CI] 0.04-0.11; p<0.0001) and standardized overall QMT score (mean change= -0.64; 95% CI 0.28-1.0); p=0.001).
Conclusions: Strength is correlated to upper and lower body functional assessments. Small but consistent changes in strength were detected over 12 months, supporting the feasibility of international multi-site training and use of strength outcomes in FSHD clinical trials.