Abstract
BackgroundCardiorespiratory 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 (VO2peak), the heart rate index (HRI), is dependent only on heart rate (HR) and was tested against oxygen uptake (VO2), either measured or predicted from conventional treadmill parameters (speed, incline, protocol time).MethodsThe HRI equation, METs = 6 x HRI– 5, where HRI = maximal HR/resting HR, provides a surrogate measure of VO2peak. Forty large scale treadmill studies were identified through a systematic search using MEDLINE, Google Scholar and Web of Science in which VO2peak was either measured (TM-VO2meas; n = 20) or predicted (TM-VO2pred; 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-VO2).ResultsThe 20 studies with measured VO2 (TM-VO2meas), involved 11,477 participants (median 337) with a total of 105,044 participants (median 3,736) in the 20 studies with predicted VO2 (TM-VO2pred). A difference of only 0.4% was seen between mean (±SD) VO2peak for TM- VO2meas and HRI-VO2 (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-VO2pred and HRI-VO2 (8.12±1.85 METs and 6.71±1.92, respectively; p<0.001).ConclusionAlthough mean TM-VO2meas and HRI-VO2 were almost identical, mean TM-VO2pred was more than 20% greater than mean HRI-VO2.
Highlights
When assessed as oxygen consumption (VO2), cardiorespiratory fitness (CRF) may be measured either using a treadmill with conventional gas analysis equipment (TM-VO2meas) or predicted from equations based on treadmill speed, incline or treadmill time (TM-VO2pred)[1]
The objective of this study was to compare aggregate heart rate index (HRI)-derived VO2 (HRI-VO2) data against VO2peak from two different treadmill tests, either: 1) VO2 measured with conventional gas analysis equipment (TM-VO2meas) or 2) VO2 predicted from equations based on treadmill speed, incline or treadmill time (TM-VO2pred)
The utility of the HRI equation [32] as a surrogate measure of VO2 expressed in METs is confirmed in this study when assessed against VO2peak for both TM-VO2meas measured with conventional gas analysis equipment and for TM-VO2pred predicted from equations based on treadmill speed, incline or treadmill time
Summary
When assessed as oxygen consumption (VO2), cardiorespiratory fitness (CRF) may be measured either using a treadmill with conventional gas analysis equipment (TM-VO2meas) or predicted from equations based on treadmill speed, incline or treadmill time (TM-VO2pred)[1]. Many factors may contribute to the error of TM-VO2pred They include 1) treadmill handrail support [9,10,11,12,13], 2) failure to use population specific equations [14,15,16,17,18], 3) inappropriate testing protocol [19,20,21], 4) delayed oxygen kinetics [22,23,24], 5) reproducibility of cardiopulmonary parameters [25,26], 6) altered mechanical efficiency with treadmill walking [27] and 7) lack of treadmill calibration [28]. Editor: Gordon Fisher, University of Alabama at Birmingham, UNITED STATES
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