Validity of peak oxygen uptake calculations from heart rate deflection points.

Two graded exercise tests on a cycle ergometer were examined in regard to their predictability of the peak oxygen uptake (VO2peak) based upon the deflection points (Dp) in the heart rate curves. The "constant duration" test (DUR-test) was based upon data from a previous maximal test. The "constant distance" test (DIS-test) was based upon the subjects' body weight and fitness level. In both tests 29 male subjects, 25 to 35 years, pedalled until exhaustion and from these tests the Dp variables (heart rate, DpHR, and the workload, DpW) and the VO2peak were determined. The subjects also underwent the Astrand & Ryhming-test (A&R-test). Deflection points could be detected for 15 subjects (52%) in the DUR-test and for 18 subjects (62%) in the DIS-test. In 13 subjects a Dp in both tests could be determined with a test-retest correlation coefficient of r = 0.66 for the DpHR and r = 0.79 for the DpW. Multiple regression analysis yielded the following equations: VO2peak = 7.7538 + 0.0199 DpW-0.0506 DpHR (n = 15; r = 0.87; SEE = 0.291.min-1) for the DUR-test and VO2peak = 5.8673 + 0.0200 DpW -0.0354 DpHR (n = 18; r = 0.88; SEE = 0.401.min-1) for the DIS-test. Compared to the measured VO2peak of the DUR-test and the DIS-test, the calculated VO2peak from the A&R-test has a correlation coefficient of r = 0.74 and r = 0.77 with a SEE of 0.57 (13.3%) and 0.55 (12.7%) l.min-1, it was concluded that, when a deflection point in the W-HR curve is found, the VO2peak can be calculated more accurately with the developed regression equations in this study than with the A&R-test. However, since the graded exercise cycle tests presented in this paper are only reliable in 33 of the 58 cases, they are useless for evaluating the VO2peak in a practicle sense, especially when no previous information about the appearance of a Dp is available.