A NEW PROCEDURE TO DETERMINE EXTERNAL POWER OUTPUT DURING HANDRIM WHEELCHAIR PROPULSION ON A ROLLER ERGOMETER - A RELIABILITY STUDY

This study presents a mathematical model by which power output (PO) de livered to the rear wheel during handrim wheelchair propulsion on a ro ller ergometer can be determined for individual wheelchair-user combin ations. PO is calculated from the torque applied to the wheel and its angular velocity. The torque applied is a function of one total intern al torque of the wheelchair-ergometer system, the rotational moment of inertia of the rear wheel, the one of the roller and its angular acce leration. The total internal torque reflects all internal friction for ces and is determined with a deceleration test. To assess the reliabil ity of this approach, 11 able-bodied subjects underwent progressively increasing exercise tests on two different occasions. PO values ranged from 72 to 63 W and were highly reliable (r(2) > 0.95). Peak physiolo gical responses were never different from test 1 and 2 (repeated measu res ANOVA; p: N.S.) and correlations were 0.90, 0.72, 0.88, 0.82, 0.70 and 0.85 for PO, oxygen uptake (VO2), heart rate, minute ventilation, carbon dioxide production and blood lactate concentration, respective ly. After an initial increase, gross mechanical efficiency dropped at higher velocities, with values ranging from 4.64 to 11.26 %. In conclu sion, the roller ergometer, the mathematical model to determine PO and the protocol used seem to be adequate to exercise test people in a ha ndrim wheelchair. It is feasible to apply the theoretical procedure to other roller ergometers which would allow for comparisons of exercise intensities and protocols between different devices used in exercise physiology acid rehabilitation.