Quantifying Real-World Upper-Limb Activity in Nondisabled Adults and Adults With Chronic Stroke

Abstract

Background: Motor capability is commonly assessed inside the clinic, but motor performance in real-world settings (ie, outside of the clinic) is seldom assessed because measurement tools are lacking.

Objective: To quantify real-world bilateral upper-limb (UL) activity in nondisabled adults and adults with stroke using a recently developed accelerometry-based methodology.

Methods: Nondisabled adults (n = 74) and adults with chronic stroke (n = 48) wore accelerometers on both wrists for 25 to 26 hours. Motor capability was assessed using the Action Research Arm Test (ARAT). Accelerometry-derived variables were calculated to quantify intensity of bilateral UL activity (ie, bilateral magnitude) and the contribution of both ULs to activity (magnitude ratio) for each second of activity. Density plots were used to examine each second of bilateral UL activity throughout the day.

Results: Nondisabled adults demonstrated equivalent use of dominant and nondominant ULs, indicated by symmetrical density plots and a median magnitude ratio of -0.1 (interquartile range [IQR] = 0.3), where a value of 0 indicates equal activity between ULs. Bilateral UL activity intensity was lower (P < .001) and more lateralized in adults with stroke, as indicated by asymmetrical density plots and a lower median magnitude ratio (-2.2; IQR = 6.2, P < .001). Density plots were similar between many stroke participants who had different ARAT scores, indicating that real-world bilateral UL activity was similar despite different motor capabilities.

Conclusions: Quantification and visualization of real-world bilateral UL activity can be accomplished using this novel accelerometry-based methodology and complements results obtained from clinical tests of function when assessing recovery of UL activity following neurological injury.

Keywords: accelerometry; bilateral upper limb activity; motor capability; motor performance; outcomes assessment; real-world activity.

Figure 1. Density plots showing 25 hours of real-world bilateral upper limb activity in three nondisabled adults

A: Total UL activity (9.6 hours) was low in this participant. B: Total UL Activity (11.9 hours) and median Bilateral Magnitude and median Magnitude Ratio values were higher in this participant. C: Total UL Activity (13.7) and median Bilateral Magnitude and Magnitude Ratio values were highest in this participant. Despite differences in total UL activity, each density plot was symmetrical in overall shape indicating that patterns of dominant and nondominant UL activity were similar.

Figure 2. Density plots showing 26 hours of real-world bilateral upper limb activity in 6 adults with stroke

Participants in the left-side column had paretic dominant ULs, while participants in the right-side column had paretic nondominant ULs. Individual data are displayed from participants with lower (A: ARAT=10, B: ARAT=10), moderate (C: ARAT=36, D: ARAT=38), and higher motor capabilities (E: ARAT=46, F: ARAT=48). Despite higher ARAT scores, the participants in C & D have similar density plots to the participants in A & B.

Figure 3. Scatterplot of ARAT score versus the median Magnitude Ratio for adults with stroke

Median Magnitude Ratio values were more negative in participants with a paretic nondominant UL (black circles) than in participants with a paretic dominant UL (red squares). There were 5 participants with a Magnitude Ratio of -7 and an ARAT score of 10. Despite a Spearman correlation of 0.66, 16/48 (33%) participants had a median Magnitude Ratio of -7, indicating that at least 50% of total UL activity consisted of nonparetic unilateral UL activity. The vertical hatched bars specify the middle 50% (i.e. 25^th and 75^th percentiles) of median Magnitude Ratio values in nondisabled adults.