Use of wrist-worn accelerometers to quantify bilateral upper limb activity and asymmetry under free-living conditions in people with multiple sclerosis

Background: Although upper limb (UL) dysfunctions are quite common among people with Multiple Sclerosis (pwMS), there is a scarcity of information about actual UL usage under free-living conditions. The aim of the present study is to quantitatively assess ‘real-world’ activity time, intensity and possible asymmetry of use among dominant and non-dominant ULs in pwMS. Methods: Twenty-eight pwMS (20 women, 8 men, average EDSS 4.3) and 28 age- and sex-matched unaffected individuals were required to wear a tri-axial accelerometer on each wrist 24h/day for 2 weekdays. Raw accelerations were processed to calculate parameters associated with time and intensity of use of UL both when engaged in uni- or bilateral activities. Results: During the 2-day monitoring period, pwMS were characterized by significantly lower overall activity, they used their dominant limb for a significantly longer time and, while performing bilateral activities, their dominant limb expressed movements of superior intensity in a proportion higher than what was observed in unaffected individuals. Conclusion: The instrumental monitoring of UL activity with two wrist-worn sensors may represent an effective tool for assessing the contribution of each limb to uni- and bilateral movements. Such data can be employed to monitor the progression of UL dysfunctions and the effectiveness of pharmacologic and rehabilitative treatments.