# Wearable Inertial Devices in Duchenne Muscular Dystrophy: A Scoping Review
## 3 Results
In contrast with previous research, there were no significant correlations between rest-activity data, SDSC (a questionnaire designed to identify sleep disturbances in pediatric populations during the previous 6 months) and PedsQL (a questionnaire adopted to register health-related QOL in both healthy children and pediatric patients). [PERSON] and colleagues [42] proposed a new relative coupling coefficient RCC to evaluate walking coordination and to distinguish between DMD and control children. 100 DMD patients and 100 control children were involved in the experimental study. Five APDM accelerometers were used for acceleration monitoring and units were positioned on forearms, shanks, and chest. The phase space reconstruction method was used to extract the non-linear dynamic feature of the monitored signals and the Local Manifold Structure Mapping method was used to estimate the RCC. Results verified the sensitivity of the proposed index to distinguish between DMD and control participants (\(p\) < 0.001). Moreover,in accordance with clinical experience, the RCC showed that the coordination ability of DMD children during gait gradually declines with age. [PERSON] and colleagues [43] monitored the total physical activity in 49 DMD patients (mean age = 13 years) for 7 consecutive days. The Actigraph GT3X accelerometer was positioned on the wrist and the ankle of participants. Results pointed to significant differences (\(p<0.001\)) in physical activity measures between DMD patients and control groups, and between ambulatory and non-ambulatory DMD patients. Moreover, results showed that locomotion ability and age can influence activity measures. The authors proposed a follow-up investigation [44] for the assessment of correlation between accelerometry measures and quantitative muscle testing (QMT). Accelerometer outcomes considered in the study were total vector magnitudes and awake vector magnitude. Results evaluated a strong Spearman's rank correlation for several variables combinations: indexed arm QMT with total wrist vector magnitude (rho(43) = 0.85, \(p<0.001\)), total indexed QMT with total wrist vector magnitude (rho(43) = 0.8, \(p<0.001\)), and indexed leg QMT with total ankle vector magnitude (rho(43) = 0.69, \(p<0.001\)). Finally, all measures significantly declined over time. In 2021, [PERSON] et al. [45] registered the step activity for 7 days in ambulatory DMD boys (70 patients, mean age = 9 years) and compared the results with a control group (10 healthy subjects, mean age = 9 years). The Actigraph GT3X accelerometer was used to monitor the activity. Results demonstrated that, if wearing the accelerometer for at least 10 h/day for two consecutive days, the collected data can predict the average weekly amount (multiple linear regression model, strength prediction represented by the adjusted R\({}^{2}\) = 0.80). On average, the 70 DMD children took 63% of daily steps compared with unaffected control boys (5147 and 8138 steps, respectively; \(p<0.01\)). To examine step activity across ages, the DMD subjects were classified into four groups based on 2-year age ranges: 5 to 6.9 years (n = 18); 7 to 8.9 years (n = 20); 9 to 10.9 years (n = 20); and 11 to 12.9 years (n = 12). An overall decline was noted with increasing age, with the three older age groups being significantly different from the first group. [PERSON] and colleagues [46] investigated the utility of wearable technologies in physical activity assessment in three pediatric diseases: Niemann-Pick C (NPC), Juvenile Idiopathic Arthritis (JIA), and Duchenne muscular dystrophy (DMD). All patients completed the 6 MWT with median results of 450 m, 325 m, and 434.5 m for the NPC, DMD, and JIA respectively. Accelerometric data were monitored with a wrist-worm accelerometer and three principal outcomes were evaluated: average daily maximum, average daily steps, and average steps per epoch. Results were compared among groups and the relationship between the 6 MWT and wearable metrics was assessed.