Reliability of cardiorespiratory measurements during wheelchair ergometry

The purpose of this research was to evaluate the stability of measures of heart rate (HR) and oxygen uptake (VO2) during repeated 30-minute bouts of constant work-rate wheelchair ergometry. Ten able-bodied subjects (seven male; three female) completed three sequential, single-stage wheelchair ergometer propulsion tests, to exhaustion, at least 48 hours apart, to determine the reliability of measurements of HR and VO2. Power output was determined as the resistance required to elicit 75% of the peak V02 attained during a peak graded exercise wheelchair ergometer test, at a propulsion velocity of three miles per hour and a flywheel roll distance of 6.32 meters. The HR and VO2 measurements were averaged over the last 30 seconds of the first (T1) and second (T2) thirds of the tests and at volitional exhaustion (T3). Significant differences were not observed at any of the data points except for HR at exhaustion. The HR at exhaustion was lower for the third test than for the second test. Intraclass correlation coefficients for HR (R=0.92, 0.95, and 0.86) and VO2 (R=0.95, 0.96, and 0.97) were high across the three tests, at all of the data points, respectively. Coefficients of variation were generally low. The results of this study indicated that, with the exception of HR during exercise sustained longer than approximately 30 minutes, VO2 and HR measurements can be made with high reliability during sustained wheelchair ergometer propulsion.