The oxygen uptake efficiency slope: what do we know?

Abstract

Purpose: To summarize what is currently known about the oxygen uptake efficiency slope (OUES) as an objective and independent submaximal measure of cardiorespiratory fitness in health and disease.

Methods: A literature search was performed within the following electronic databases--PubMed, Cochrane Library, Embase, Web of Science, CINAHL, PsycINFO, Scopus, and MEDLINE--using the search terms "OUES," "oxygen uptake efficiency slope," and "ventilatory efficiency." The search identified 51 articles. Selection, evaluation, and data extraction were accomplished independently by 2 authors.

Results: Twenty-four studies satisfied all inclusion criteria: 17 cross-sectional studies and 7 intervention studies. The results indicated that the OUES is relatively independent of exercise intensity, correlates highly with other exercise parameters, appears to have discriminative value, and is sensitive to the effects of physical training in patients with cardiac disease. Oxygen uptake efficiency slope values are considerably influenced by anthropometric variables and show large interindividual variation.

Conclusion: Oxygen uptake efficiency slope is an independent and reproducible measure of cardiorespiratory function that does not require maximal exercise. It greatly reduces test variability because of motivational and subjective factors and is reliable and easily determinable in all subjects. Although OUES appears not interchangeable with maximal parameters of cardiopulmonary function, it seems to be a useful submaximal alternative in subjects unable to perform maximal exercise.