The mean maximal perceived exertion was 18.9 ± 1.3 and the maximal respiratory exchange ratio was 1.16 ±0.14 (Table 2). These values suggest that maximal exercise was generally achieved for the group. The mean maximal heart rate attained was 168 ±17 which is roughly equal to that expected for age. Maximal oxygen uptake was 33.1 ±10.7; male subjects achieved approximately 100% of that expected for sex and age, while female subjects achieved approximately 93% of that expected for sex and age.
Relation Between Oxygen Uptake and Work Rate
Figure 2 illustrates the relationship between minute by minute changes in measured oxygen uptake and those predicted by the work rate. The slope of the relationship for all subjects was 0.78 (SEE = 0.008 ml/kg/min, p<0.001), and the correlation was 0.93 (SEE = 4.0, p<0.001). The regression equation was Y=.79X + 3.02. The slope of the relationship did not differ between values observed below 5 min of exercise (slope = 0.78, SEE = 0.015, r = 0.85, SEE = 3.23, p<0.001), and those above 5 min of exercise (slope = 0.73, SEE = 0.014, r = 0.76, SEE = 4.66, p<0.001).
Predicted vs Measured Maximal Oxygen Uptake
Figure 3 illustrates the relationship between maximal ventilatory oxygen uptake and oxygen uptake predicted from peak treadmill speed and grade. The correlation coefficient between the two variables was 0.87 (SEE=4.35 mg/kg/min, P<0.001). The regression equation was Y=0.72X+3.67.