Spinal Bulbar Muscular Atrophy (SBMA): a cross-sectional analysis of wearable sensors during the 6-minute walk (6MWT) and timed up and go (TUG) tests

Spinal bulbar muscular atrophy (SBMA) is a rare, X-linked inherited neuromuscular disease, caused by a CAG repeat expansion in the first exon of the androgen receptor gene, that affects males. Symptoms begin with hand tremors and lower proximal muscle weakness and slowly progress to dysphagia, dysarthria, and dysphonia. The 6-minute walk test (6MWT) and timed up and go (TUG) are used to assess motor capacity in people with SBMA. The 6MWT measures the distance (m) walked in 6 minutes and the TUG measures the time (s) it takes an individual to stand up, walk 3m, turn around, and sit down. Wearable sensors could be used in future therapeutic SBMA trials to objectively analyze gait and balance. This study aims to describe the wearable sensors’ ability to measure motor capacity from the baseline instrumented-6MWT (i-6MWT) and -TUG (i-TUG) in individuals with SBMA. This study had 18 male participants with a mean age of 61.8 ± 6.68 years — 4 healthy controls (H), 5 with SBMA who did not use assistive devices (S), and 8 with SBMA who used assistive devices (SD). All 18 individuals participated in the i-6MWT. For the i-6MWT, the distance (m) walked ranged from: (H) 477-653, (S) 400-584, and (SD) 236-373. The i-6MWT percent norms ranged from: (H) 81.5-122, (S) 80.3-108, and (SD) 42.5-68.4. Cadence (steps/min) ranged from: published norms (N) 103-133, (H) 109 – 140, (S) 103-133, and (SD) 74.8-119. Gait speed (m/s) ranged from: (N) 1.04-1.64, (H) 1.22-1.67, (S) 1.05-1.56, and (SD) 0.60-0.99. Only participants with SBMA completed the i-TUG. i-TUG duration (s) ranged from: published norms (N) 6.28-11.6, (S) 5.09-8.98, and (SD) 8.91-27.9. Turn velocity ranged from: (N) 158 – 322, (S) 188 – 305, and (SD) 85.4-239. Stand to sit duration(s) ranged from: (N) 0.49-1.06, (S) 0.49-0.80, and (SD) 0.56-1.15. Longitudinal studies examining the i-6MWT and i-TUG in larger sample sizes are needed to validate the use of wearable sensors as an effective outcome measure for SBMA clinical trials. Spinal bulbar muscular atrophy (SBMA) is a rare, X-linked inherited neuromuscular disease, caused by a CAG repeat expansion in the first exon of the androgen receptor gene, that affects males. Symptoms begin with hand tremors and lower proximal muscle weakness and slowly progress to dysphagia, dysarthria, and dysphonia. The 6-minute walk test (6MWT) and timed up and go (TUG) are used to assess motor capacity in people with SBMA. The 6MWT measures the distance (m) walked in 6 minutes and the TUG measures the time (s) it takes an individual to stand up, walk 3m, turn around, and sit down. Wearable sensors could be used in future therapeutic SBMA trials to objectively analyze gait and balance. This study aims to describe the wearable sensors’ ability to measure motor capacity from the baseline instrumented-6MWT (i-6MWT) and -TUG (i-TUG) in individuals with SBMA. This study had 18 male participants with a mean age of 61.8 ± 6.68 years — 4 healthy controls (H), 5 with SBMA who did not use assistive devices (S), and 8 with SBMA who used assistive devices (SD). All 18 individuals participated in the i-6MWT. For the i-6MWT, the distance (m) walked ranged from: (H) 477-653, (S) 400-584, and (SD) 236-373. The i-6MWT percent norms ranged from: (H) 81.5-122, (S) 80.3-108, and (SD) 42.5-68.4. Cadence (steps/min) ranged from: published norms (N) 103-133, (H) 109 – 140, (S) 103-133, and (SD) 74.8-119. Gait speed (m/s) ranged from: (N) 1.04-1.64, (H) 1.22-1.67, (S) 1.05-1.56, and (SD) 0.60-0.99. Only participants with SBMA completed the i-TUG. i-TUG duration (s) ranged from: published norms (N) 6.28-11.6, (S) 5.09-8.98, and (SD) 8.91-27.9. Turn velocity ranged from: (N) 158 – 322, (S) 188 – 305, and (SD) 85.4-239. Stand to sit duration(s) ranged from: (N) 0.49-1.06, (S) 0.49-0.80, and (SD) 0.56-1.15. Longitudinal studies examining the i-6MWT and i-TUG in larger sample sizes are needed to validate the use of wearable sensors as an effective outcome measure for SBMA clinical trials.