Accelerometer cut-points derived during over-ground walking in persons with mild, moderate, and severe multiple sclerosis.

BACKGROUND

There has been increased interest in objectively quantifying time spent in moderate-to-vigorous physical activity (MVPA) using accelerometry as an outcome among persons with multiple sclerosis (MS). This requires development of a cut-point for interpreting the rate of accelerometer output based on its association with energy expenditure during physical activity.

OBJECTIVE

The current study measured activity counts from a waist-worn accelerometer and energy expenditure based on indirect calorimetry during three speeds of over-ground walking for deriving cut-points for interpreting accelerometer output in persons with mild, moderate, and severe MS disability.

METHODS

54 participants with MS initially completed a neurological examination for generation of an EDSS score. Participants were then fitted with an ActiGraph model GT3X+ accelerometer and a Cosmed portable metabolic system, and completed three, 6-minute walk (6 MW) tests that were interspersed with 10-15 min of rest. The first 6 MW was undertaken at a comfortable walking speed (CWS), and the two remaining 6 MW tests were undertaken above (faster walking speed) or below (slower walking speed) the participant's CWS in a counterbalanced order.

RESULTS

The linear association between activity counts per minute and energy expenditure did not differ between persons with mild and moderate MS disability, but it was significantly different among persons with severe disability. This resulted in disability-specific cut-points for MVPA of 1980 and 1185 counts per minute for groups with mild/moderate disability and severe disability, respectively.

CONCLUSIONS

We believe that this research will facilitate a better understanding of time spent in MVPA across a broad range of MS disability.