Arm-crank propelled three-wheeled chair: physiological evaluation of the propulsion using one arm and both arm patterns.

Disabled people in India frequently use the arm-crank propelled three-wheeled chair (ACWC) for outdoor transportation. Two models of these chairs are commercially available: one is powered by cranking using one arm (ACWC-1) and the other uses both arms (ACWC-2). The purpose of the study was to compare the efficiency of the two types of propulsion with respect to the standard physiological responses and, consequent upon the findings, to recommend the use of a suitable one. The energetics of locomotion of the users at their freely chosen speed (FCS) were measured and compared with changes in the physiological parameters in the within-subject groups. The study was conducted in outdoor settings to simulate the actual locomotive conditions encountered by the users in their practical life. 14 males, who had been regular and proficient users of both propulsion systems for more than last six years and who had a history of paraplegia (below the 10th thoracic vertebra, n=11) and poliomyelitis (n=3) participated in the study. The subjects were required to propel the test chair (a combination of both the propulsion systems built in a single model) on an oval track of 358 m circumference at their FCS for 5 min; ambulatory data were collected during last 3 min of exercise and averaged. The FCS (m/min), heart rates (bpm) and oxygen uptake (l/min) were measured. Physiological cost index (b/m) oxygen consumption (ml/kg/min), oxygen cost (ml/kg/m) and net locomotor energy cost (kcal/kg/km) of the two sets of observations were derived and compared using a t-test for the paired observations. The FCS was significantly higher and the physiological parameters were lower with the ACWC-2 than with ACWC-1, except for heart rate and oxygen consumption, where the difference was not significant . It is concluded that two-arm use is more efficient and less physically demanding than one-arm use in the arm-crank propulsion system and that the former is more suitable for efficient ambulation.