How Accurate Is the Prediction of Maximal Oxygen Uptake with Treadmill Testing?

BACKGROUND: Cardiorespiratory fitness measured by treadmill testing has prognostic significance in determining mortality with cardiovascular and other chronic disease states. The accuracy of a recently developed method for estimating maximal oxygen uptake (VO(2peak)), the heart rate index (HRI), is dependent only on heart rate (HR) and was tested against oxygen uptake (VO(2)), either measured or predicted from conventional treadmill parameters (speed, incline, protocol time). METHODS: The HRI equation, METs = 6 x HRI– 5, where HRI = maximal HR/resting HR, provides a surrogate measure of VO(2peak). Forty large scale treadmill studies were identified through a systematic search using MEDLINE, Google Scholar and Web of Science in which VO(2peak) was either measured (TM-VO(2meas); n = 20) or predicted (TM-VO(2pred); n = 20) based on treadmill parameters. All studies were required to have reported group mean data of both resting and maximal HRs for determination of HR index-derived oxygen uptake (HRI-VO(2)). RESULTS: The 20 studies with measured VO(2) (TM-VO(2meas)), involved 11,477 participants (median 337) with a total of 105,044 participants (median 3,736) in the 20 studies with predicted VO(2) (TM-VO(2pred)). A difference of only 0.4% was seen between mean (±SD) VO(2peak) for TM- VO(2meas) and HRI-VO(2) (6.51±2.25 METs and 6.54±2.28, respectively; p = 0.84). In contrast, there was a highly significant 21.1% difference between mean (±SD) TM-VO(2pred) and HRI-VO(2) (8.12±1.85 METs and 6.71±1.92, respectively; p<0.001). CONCLUSION: Although mean TM-VO(2meas) and HRI-VO(2) were almost identical, mean TM-VO(2pred) was more than 20% greater than mean HRI-VO(2).