Application and Reliability of Accelerometer-Based Arm Use Intensities in the Free-Living Environment for Manual Wheelchair Users and Able-Bodied Individuals

Abstract

Arm use in manual wheelchair (MWC) users is characterized by a combination of overuse and a sedentary lifestyle. This study aimed to describe the percentage of daily time MWC users and able-bodied individuals spend in each arm use intensity level utilizing accelerometers. Arm use intensity levels of the upper arms were defined as stationary, low, mid, and high from the signal magnitude area (SMA) of the segment accelerations based on in-lab MWC activities performed by eight MWC users. Accelerometry data were collected in the free-living environments from forty MWC users and 40 sex- and age-matched able-bodied individuals. The SMA intensity levels were applied to the free-living data and the percentage of time spent in each level was calculated. The SMA intensity levels were defined as, stationary: ≤0.67 g, low: 0.671-3.27 g, mid: 3.27-5.87 g, and high: >5.871 g. The dominant arm of both MWC users and able-bodied individuals was stationary for most of the day and less than one percent of the day was spent in high intensity arm activities. Increased MWC user age correlated with increased stationary arm time (R = 0.368, p = 0.019). Five and eight days of data are needed from MWC users and able-bodied individuals, respectively, to achieve reliable representation of their daily arm use intensities.

Keywords: free-living data collection; inertial measurement units; spinal cord injury; upper extremity; wearable sensors.

Figure 1

The purpose, data collection, and data processing flow of defining signal magnitude area (SMA) arm use intensity levels for the in-lab and free-living data utilized in this study.

Figure 2

Three inertial measurement units (IMU) were secured to all participants on both of their lateral arms and their chest using elastic straps. The circles indicate where the IMUs are attached. Note: The individual pictured is study staff and not a research participant.

Figure 3

Representative signal magnitude area (SMA) data from one participant completing three counter height reaches, three overhead reaches, three cross body lifts, two transfers, level propulsion and incline propulsion in a structured lab setting for their dominant (black line) and non-dominant (blue line). The shaded areas represent the am use intensity levels (red: stationary, orange: low, yellow: mid, green: high).

Figure 4

The effect of age on the percentage of daily time spent stationary and in the low arm use intensity levels for the MWC and control cohorts on the dominant arm: (A) MWC stationary, (B) MWC low arm use intensity level, (C) control stationary, (D) control low arm use intensity level.