Assessing movement quality in individuals with Duchenne muscular dystrophy utilizing accelerometry: Comparisons with...

Duchenne muscular dystrophy (DMD) is characterized by progressive decline in skeletal muscle function leading to loss of ambulation and premature cardiopulmonary failure. The ability to monitor declines in skeletal muscle function in a free-living setting would be advantageous. Prior studies have utilized accelerometer measures of movement quantity (e.g., counts per minute, fraction of activity time), but accelerometry research on measures of movement quality in DMD is limited. The aim of the study was to compare quality of movement between a healthy control cohort and individuals with DMD using accelerometry. Accelerometer data were obtained from one study visit for each healthy control (N = 92; ActiGraph Link GT9X, GT3X-BT or a combination) and one to three study visits for each participant with DMD (N = 100; Link GT9X). Measures included counts per minute, entropy, jerk, and movement frequency (mean and standard deviation). Median (IQR) of each measure was reported for each group, including healthy controls and both ambulatory and non-ambulatory DMD participants, and significant differences across each group were compared using Mann-Whitney U tests. Correlations were assessed between accelerometer measures of movement quantity and quality, and predictive change in DMD ambulatory status was assessed using longitudinal regression. Significant differences (P < 0.01) were observed in all measures between healthy controls, ambulatory DMD, and non-ambulatory DMD participants. Most measures were lower in DMD participants, suggesting decreased movement. Movement frequency values were higher in DMD (Healthy Controls 3.19 [3.05-3.45], Ambulatory DMD 3.60 [3.43-3.89], Non-Ambulatory DMD 4.32 [4.04-4.52]), suggesting more disordered movements. Counts per minute correlated strongly with both jerk (r: 0.722, P < 0.05) and mean frequency (r: -0.813, P < 0.05). Matched to age, individuals with DMD produce progressively fewer and more disordered (lower quality) movement compared to healthy individuals. Significantly lower entropy and jerk may be explained by a progressive decline in the strength of movements produced by individuals with DMD.