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Data were entered into a spreadsheet (Quattro Pro) from which means and standard deviations were performed. A program (Statistical Graphics Corporation, Bethesda, Md) was used to compare regression lines between oxygen uptake and work rate. Students t-tests for paired observations were used to evaluate differences between measured and predicted maximal oxygen uptake.

Results
All subjects completed the 2 exercise tests without complication. Hemodynamic and gas exchange variables at rest and maximal exercise for all subjects are presented in Table 2. Characteristics of the ramp test are presented in Table 3. Table 4 contrasts the regression equations and correlations between measured oxygen uptake and treadmill time in the present and previous studies. The relationship between measured and predicted oxygen uptake throughout exercise is illustrated in Figure 2. The relationship between measured and predicted maximal oxygen uptake is illustrated in Figure 3. Figure 4 compares maximal MET values predicted from a specific activity questionnaire vs those achieved on the treadmill.

Table 2—Hemodynamic and Gas Exchange Data at Best and Maximal Exercise

 Author Protocol RegressionEquation Mean Maximal Uptake ±SD, ml/kg/min r Standard Error of the Estimate Bruce et al Bruce Y = 3.29X + 4.07 37.3 ±8.2 0.93 34.9 Pollock et al Bruce Y = 4.33X —4.66 40.0 ±7.2 0.88 0.096 Balke Y=1.44X+14.99 39.4 ±5.9 0.92 0.25 Roberts et al* Modified 36.8±6.6 0.93 2.56 Balke Y = 3.91X —8.88 Froelicher et al Bruce Y=3.18X—0.59 44.5 ±5.8 0.82 3.34 Martin et al Balke Y = 1.25X + 9.42 41.6±5.0 0.86 2.65 Myers et al (present study) Ramp Y=.72X+.3.67 33.1 ±10.7 0.87 4.35

Table 3—Characteristics of the Ramp Test

 Data Mean ± SD Rest Heart rate, beats/min 66± 11 Systolic blood pressure, mm Hg 136 ±20 Diastolic blood pressure, mm Hg 88± 16 Maximal exercise Heart rate, beats/min 168 ±17 Systolic blood pressure, mm Hg 203 ±21 Diastolic blood pressure, mm Hg 90± 13 Perceived exertion 18.9± 1.3 Ventilation, L/min, BTPS 101.9 ±35 Oxygen uptake, L/min, STPD 2.819 ±0.952 Oxygen uptake, ml/kg/min 33.13 ±10.7 COz production, L/min, STPD 3.288± 1.199 Respiratory exchange ratio 1.16±0.14

Table 4 ’—Comparison of the Ramp Treadmt to Previous Studies Relating Treadmill Time or Workload to Measured Oxygen Uptake in Normal Subjects

 Mean ± SD Range Ramp rate, % grade/min 2.32 ±0.82 0.5-4.1 Rate of change in speed, mph/min 1.18 ±0.45 0.4-2.4 Peak speed, mph 3.3 ±0.4 2.5-4.5 Peak grade, % 16.0±5.6 3.5-25 Peak treadmill time, min 9.47 ±1.8 5.4-14.7 Peak predicted maximal oxygen uptake, ml/kg/min 37.7 ±10.7 18.4-60.3 Figure 2. The relationship between measured and predicted oxygen uptake each minute throughout exercise. The correlation coefficient between the two variables was 0.93 (SEE = 3.96 ml/kg/ min, p. Figure 3. The relationship between measured and predicted maximal oxygen uptake. The correlation coefficient between the two was 0.87 (SEE = 4.35 ml/kg/min), p <0.001). The regression equation was Y = 0.72X + 3.67. Figure 4. The relationship between exercise capacity, expressed in METs, estimated from a specific activity questionnaire (Y axis) and that calculated from treadmill speed and grade at peak exercise (X axis). Print this Page