# Wearable Inertial Devices in Duchenne Muscular Dystrophy: A Scoping Review
## 3 Results
Results pointed to a strong and significant correlation between the cumulative jerk and the clinical score ([PERSON]'s rho(7) = \(-\)0.97, \(p\) < 0.001 for the Brooke Upper Extremity Scale, [PERSON]'s rho(7) = 0.81, \(p\) < 0.03 with the arm function scores for the DMD Functional Ability Self-Assessment Tool). Jerk values also had a very strong or strong correlation with elbow flexion strength (non-dominant arm: [PERSON]'s r(7) = 0.931, \(p\) = 0.002; dominant arm: [PERSON]'s rho(7) = 0.75, \(p\) = 0.052). Similar promising results were obtained by [PERSON] and colleagues [39] in the home monitoring of 16 DMD patients (age 7-17 years). Physical activity was monitored for 1-3 days. Three MOX accelerometers were used for monitoring, positioned on the patient's wheelchair, the upper arm and the lower arm. Three principal outcome variables were analyzed: the intensity of activity, the level of arm elevation, and the elevation rate. The intensity of activity was calculated by integrating the acceleration during 1-minute episodes and summing this outcome over all three axes. The level of elevation was referred to the orientation of the arm during a period of 1 s. Data were categorized as low (<45\({}^{\circ}\)), middle (45\({}^{\circ}\)-90\({}^{\circ}\)), or high (>90\({}^{\circ}\)) elevation of the arm according to the upper arm sensor. The elevation rate was referred to the frequency of elevation of the arm from low to middle elevation and from middle to high elevation. Clinical scores were registered with the Brooke and PUL scales. A remarkably high correlation was obtained between the intensity of activity monitored at the upper arm and the lower arm ([PERSON]'s rho(15) = 0.95, \(p\) < 0.01). Moreover, there was a significantly high correlation between intensity and PUL scale score (lower arm: [PERSON]'s rho(15) = 0.82, \(p\) < 0.01; upper arm: [PERSON]'s rho(15) = 0.84, \(p\) < 0.01). There was a moderate correlation between number of transfers per hour and PUL scale score from low-middle ([PERSON]'s rho(15) = 0.59, \(p\) < 0.05) to middle-high ([PERSON]'s rho(15) = 0.69, \(p\) < 0.01) and a high correlation between the total number of transfers per hour and the PUL scale score ([PERSON]'s rho(15) = 0.76, \(p\) < 0.01). The short communication written by [PERSON] and colleagues [40] pointed out and discussed the fact that European regulators provided an update on the recent regulatory consideration of a new endpoint that could be used in DMD therapeutic trials. Previously, regulators recognized the loss of ambulation as an important DMD milestone and the 6 MWT as an endpoint. Five Gait Variables were assessed for their validity in measuring a patient's locomotion ability: the 95 th centile of the stride velocity (SV95C), the median stride velocity, the 95 th centile of the stride length, the median stride length, and the distance walked/recorded hour. Accuracy, reliability, and sensitivity of the Gait Variables were tested and discussed. European regulators considered that, for ambulatory DMD patients (5 years of age and above), SV95C is a reliable secondary endpoint when measured continuously in a home environment by a valid and suitable wearable device. In 2020, [PERSON] and colleagues [41] used a wearable device to assess the sleep and motor function in DMD patients. The aim of the study was to describe the sleep impairment and its relationship with quality of life, and to evaluate relationships between rest-activity parameters, sleep quality, and 6 MWT performance. A total of 54 DMD patients participated in the experimental study, but only 23 patients were enrolled in the actigraphy monitoring. The actigraphy Activatch 2 was used to quantify activity parameters. Participants wore the Activatch 2 for up to 10 days on their non-dominant wrist. Non-ambulatory participants had significantly lower sleep efficiency (percentage of time scored as sleep during time spent in bed), less wake time after sleep onset (minutes scored as wake during a sleep period), and less daytime activity than those in the ambulatory group.