Validity of Submaximal Step Tests to Estimate Maximal Oxygen Uptake in Healthy Adults

Hunter Bennett, Gaynor Parfitt, Kade Davison, Roger Eston

Aerobic capacity (VO2max) is a strong predictor of health and fitness and is considered a key physiological measure in the healthy adult population. Submaximal step tests provide a safe, simple and ecologically valid means of assessing VO2max in both the general population and a rehabilitation setting. However, no studies have attempted to synthesize the existing knowledge regarding the validity of the multiple step-test protocols available to estimate VO2max in the healthy adult population. The objective of this study was to systematically review literature on the validity and reliability of submaximal step-test protocols to estimate VO2max in healthy adults (age 18-65 years). A systematic literature search of the MEDLINE, EMBASE, Scopus, Web of Science, and Cochrane Library databases was performed. The search returned 690 studies that underwent the initial screening process. To be included, the study had to (1) have participants deemed to be healthy and aged between 18 and 65 years; (2) assess VO2max by means of a submaximal step test against a graded exercise test (GXT) to volitional exhaustion; and (3) be available in English. Reference lists from included articles were screened for additional articles. The primary outcome measures used were the validity statistics between the actual measured VO2max and predicted VO2max values, and the reported direction of the statistically significant difference between the measured VO2max and the predicted VO2max. The Quality Assessment Tool for Quantitative Studies was used to assess the risk of bias in each included study, and was adapted to the type of quantitative study design used. The combined database search produced 690 studies, from which 644 were excluded during the screening process. Following full-text assessment, a further 39 studies were excluded based on the eligibility criteria detailed previously. Four additional studies were located via the reference lists of the included studies, leaving 11 studies that fulfilled the inclusion criteria and which compared eight different step-test protocols against a direct measure of VO2max incurred during a maximal GXT. Validity measures varied, with a broad range of correlation coefficients reported across the 11 studies (r = 0.469-0.95). Of the 11 studies, two reported reliability measures, demonstrating good test-retest reliability [mean -0.8 ± 3.7 mL kg(-1) min(-1) (±7.7 % of the mean measured VO2max)]. Considering the relationship between VO2max and various markers of health, the use of step tests as a measure of health in both the general adult population and rehabilitation settings is advocated. Step tests provide a simple, effective and ecologically valid method of submaximally assessing VO2max that can be implemented in a variety of situations within the general adult population. Future research is needed to assess the reliability of the majority of the step-test procedures reviewed. Based on the validity measures, submaximal step-test protocols are an acceptable means of estimating VO2max in the generally healthy adult population. For tracking changes in cardiorespiratory fitness, the Chester Step test appears to be an appropriate tool due to its high test-retest reliability.