Power output for wheelchair driving on a treadmill compared with arm crank ergometry

The limiting factors with regard to power output available for wheelchair ambulation have not been identified. The aim of the present study was to correlate power output during wheelchair driving with (i) power output and oxygen uptake during arm crank ergometry and (ii) arm muscle strength.

Eleven disabled men were examined for maximal power output (POmax) during wheelchair driving on a treadmill and during arm crank ergometry. Oxygen uptake (VO2) was recorded at submaximal and maximal arm crank ergometry in all men and during submaximal wheelchair driving on a treadmill in four men. Power output during wheelchair driving on a treadmill was measured. Static and dynamic elbow muscle strength was measured isokinetically.

POmax was significantly lower (P < 0.001) for wheelchair driving (109 (31) W; mean (SD)) than for arm ergometry (163 (49) W). There was a significant correlation between POmax for arm crank ergometry and wheelchair driving (r = 0.73). There was no correlation between POmax and elbow strength. The mechanical efficiency was constant for the different levels on the arm crank ergometry test. The submaximal testing showed a consistently lower mechanical efficiency for wheelchair driving than for arm crank ergometry.

It is suggested that the lower level of power output for wheelchair driving is fully explained by the lower mechanical efficiency. Any improvement in power output available for ambulation must be based on wheelchair ergonomics.