Validity of criteria for establishing maximal O2 uptake during ramp exercise tests

The incremental or ramp exercise test to the limit of tolerance has become a popular test for determination of maximal O-2 uptake ((V)over dotO(2max)). However, many subjects do not evidence a definitive plateau of the 02 work rate relationship on this test and secondary criteria based upon respiratory exchange ratio (RER), maximal heart rate (HRmax) or blood [lactate] have been adopted to provide confidence in the measured (V)over dotO(2max) We hypothesized that verification Of (V) over dotO(2max) using these variables is fundamentally flawed in that their use could either allow underestimation Of (V) over dotO(2max) (if, for any reason, a test were ended at a sub-maximal (V) over dotO(2max), or alternatively preclude subjects from recording a valid (V) over dotO(2max). Eight healthy male subjects completed a ramp exercise test (at 20 W/min) to the limit of tolerance on an electrically braked cycle ergometer during which pulmonary gas exchange was measured breath-by-breath and blood [lactate] was determined every 90 s. Using the most widely used criterion values of RER (1.10 and 1.15), (V) over dotO(2max) as determined during the ramp test (4.03 +/- 0.10 l/min) could be under-measured by 27% (2.97 +/- 0.24 l/min) and 16% (3.41 +/- 0.15 l/min), respectively (both P < 0.05). The criteria of HRmax (age predicted HRmax +/- 10 b/min) and blood [lactate] (>= 8 mM) were untenable because they resulted in rejection of 3/8 and 6/8 of the subjects, most of whom (5/8) had demonstrated a plateau of 1 02max at (V) over dotO(2max). These findings provide a clear mandate for rejecting these secondary criteria as a means of validating (V) over dotO(2max) on ramp exercise tests.