Background: Accelerometers are accurate tools to assess movement and physical activity. However, interpreting standardly used outputs is not straightforward for populations with impaired mobility.Methods: The applicability of GENEActiv was explored in a group of 30 participants with myotonic dystrophy and compared to a group of 14 healthy-controls. All participants performed a set of tests while wearing four different accelerometers (wrists and ankles):  standing still;  ten-meters walk test;  six-minutes walking test; and,  ten-meters walk/run test.Results: Relevant findings were:  high intra-accelerometer reliability (i.e. 0.97 to 0.99; p < 0.001);  each test acceleration values differ significantly between each other;  no inter-accelerometer reliability between wrist-worn devices and ankle-worn; and  a significant difference between the myotonic dystrophy group and the healthy-controls detectable at each test (i.e. Left-ankle values at six-minutes walking test: 48±17 for the myotonic dystrophy group, vs, 74±16 for the healthy-controls; p < 0.001).Conclusions: GENEActiv demonstrated to be valid and reliable, capable of detecting walking periods and discriminating different speeds. However, inter-accelerometer reliability only applied when comparing opposite sides of the same limb. Specific movement characteristics of the myotonic dystrophy group were identified and muscle strength showed not to be a full determinant of limb acceleration.Implications for rehabilitationRehabilitation professionals in the field of neuromuscular disorders should be aware of the potential use of objective monitoring tools such as accelerometers whilst acknowledging the implications of assessing populations with altered movement patterns.Researchers should be cautious when translating accelerometry outputs previously validated in healthy populations to functionally impaired cohorts like myotonic dystrophy.Accelerometers can objectively expose movement disturbances allowing further investigations for the source of these disturbances.
Keywords: Accelerometer; DM1; GENEActiv; Myotonic Dystrophy; activity monitor and walking speed.