Effect of work rate increment on peak oxygen uptake during wheelchair ergometry in men with quadriplegia

The purpose of this study was to determine the effect of work rate increment on peak oxygen uptake (VO2 peak) during wheelchair ergometry (WCE) in men with quadriplegia due to cervical spinal cord injuries (CSCI). Twenty-two non-ambulatory subjects (aged 20-38 years) with CSCI were divided into two groups based on wheelchair sports classification (n = 12 for IA group and n = 10 for IB/IC group). Subjects underwent three different, continuous graded exercise tests (spaced at least 1 week apart) on an electronically braked wheelchair ergometer. Following a 3-min warmup, the work rate was increased 2, 4, or 6 W.min-1 for the IA group and 4, 6, or 8 W.min-1 for the IB/IC group. Ventilation and gas exchange were measured breath-by-breath with a computerized system. Repeated-measures ANOVA showed no significant difference among the three protocols for VO2 peak in the IA group (P greater than 0.05). The mean (SD) VO2 peak values (ml.kg-1.min-1) were 9.3 (2.4), 9.4 (3.2), and 8.4 (2.6) for the 2, 4, and 6 W.min-1 protocols, respectively. In contrast, the IB/IC group showed a significant difference among the protocols for VO2 peak (P less than 0.05). The mean (SD) VO2 peak values (ml.kg-1,min-1) were 15.1 (4.0), 14.1 (4.4), and 12.7 (4.0) for the 4, 6, and 8 W.min-1 protocols, respectively. Post hoc analysis revealed a difference between the 4 and 8 W.min-1 protocols. Our results suggest that graded exercise testing of men with quadriplegia due to CSCI, using WCE, should employ work rate increments between 2 and 6 W.min-1 and that work rate increments of 8 W.min-1 or greater will result in an underestimate of VO2 peak.