Push-rate threshold for physical activity intensity in persons who use manual wheelchairs

ABSTRACT: There is evidence that manual wheelchair users are among the least physically active in society. However, the current cut points for quantifying physical activity intensity based on steps per minute have been developed for ambulatory adults from the general population and other clinical populations and may not be appropriate or applicable for manual wheelchair users. This study examined the association between push rate (an analog of step rate) and energy expenditure across three speeds of treadmill wheelchair propulsion among manual wheelchair users and further generated a push-rate cut point for quantifying moderate-to-vigorous physical activity. Persons who used manual wheelchairs (N = 17) performed three, 6-min bouts of manual wheelchair propulsion on a motor-driven treadmill at speeds of 0.7, 1.3, and 2.0 m/sec. Push rate per trial was measured using SMARTwheels, and the rate of oxygen consumption per trial was measured using a portable metabolic system. The mean (SD) R2 value for the relationship between push rate and energy expenditure was 0.78 (0.14). The mean (SD) push-rate cut point for quantifying moderate-to-vigorous physical activity was 55.05 (26.06) pushes/min. This preliminary study provides the first push-rate cut point for quantifying moderate-to-vigorous physical activity among a heterogeneous sample of manual wheelchair users. This threshold may be important for public health promotion and individual-level monitoring and prescription of free-living physical activity behavior among manual wheelchair users.