Myotonic dystrophy (DM), caused by an expansion of the DMPK gene often leads to weakness, myotonia, and gait impairments. This exploratory pilot study evaluated stride level ambulation and balance metrics from a wearable to identify gait-specific changes during the Six-Minute Walk Test (6MWT). Participants were recruited at MDF’s 2023 conference and wore bilateral ankle-worn Syde® devices alongside video kinematics with OpenCap during the 10 Meter Walk/Run Test (10MWRT), Timed Up and Go (TUG), 5-times Sit-to-Stand (5xSTS), and 6MWT. Data analysis included digital variables associated with gait velocity and balance, cross-validating Syde recorded distances against clinical measures and kinematics with disease severity.
This pilot study enrolled 8 participants (75% male, DM1=7, DM2=1) with a median age of 44.5 years (range: 34.9–58.1; mean: 45.6+/-6.9), a median disease duration of 21.9 years (10.7+/-37.7), and symptom onset of 23.7 years (7.4+/-39.5). Among those with genetic data (n=6), the median CTG repeat length was 265 (range: 120–1000; mean: 407+/-358). Functional testing yielded a median 6MWT distance of 460 m (range: 294–600; mean: 434.1 +/-102.6) and a median fatigue index of 5.7 (range: 2.1–17.9). Correlation analysis revealed a significant relationship between 10-meter walk speed and 6MWT distance (r=0.76, p=0.03). The Syde® wearable device demonstrated high analytical validity, successfully reconstructing 6MWT trajectories with minimal angular error (0.5 to 2.1°). Peak stride velocity, stride length variability, and mediolateral sway were identified as objective indicators of gait velocity and balance.
Wearable-derived kinematics complemented traditional outcomes, showing strong associations with both the TUG and 10MWRT. This pilot study indicates that wearables can quantify disease-specific changes in stride velocity and balance which are often missed by distance or time metrics alone. These early findings support the need for larger studies to validate digital measures and real world integration or sensitivity tracking of progression.