Measuring expired gases (EGs) while performing a maximal (max) effort exercise test is considered the most accurate evaluation of VO2 max. This methodology is not applicable for all populations. Submaximal (sub-max) protocols not measuring expired gases are more applicable, however their ability to accurately predict VO2max is not clear. PURPOSE: To compare VO2max results from 1) University of Houston Non-Exercise Test (UHNET), 2) McArdle Step Test (MST), 3) Bruce Protocol measuring EGs to max (Bruce-EGs), and 4) Bruce Protocol using time to max (Bruce-TM). METHODS: Recreationally active men and women {n= 24 (16M/8W); age = 25±7.7 years; body mass = 74.5±10.9kg; BMI = 24.3±2.9} completed 4 tests (on the same day) in the following order: 1) UHNET, 2) MST, 3) Bruce-EGs, and 4) Bruce-TM. For the UHNET, participants rated his/her physical activity (PAR). This was followed with a specified equation to estimate the participants VO2 max based on their PAR, age, BMI, and gender. Upon completion of the UHNET, participants performed the MST. The MST required participants to step on a 16.25inch bench at a specific cadence (different for men and women) for 3 minutes. Five seconds following the MST, radial pulse (RP) was assessed for 15 seconds. The radial pulse was converted to HR (beats/min) using the formula (RP*4). To estimate VO2max from the MST, the HR value was applied to a specific equation (different for men and women). Ten minutes after completing the MST, participants performed the Bruce protocol to max. For the Bruce Protocol, VO2max was calculated via 1) measurement of EGs and 2) the time it took to achieve max (TM). Expired gases were measured using a metabolic cart (Parvo Medics TrueOne 2400). To estimate VO2max using TM, the Bruce Protocol Time Formula (different for men and women) was applied. In addition to EGs and TM, HRmax, and Respiratory Exchange Ratio (RER) were assessed. Significant differences (p2 (Bruce-EGs) and estimated VO2 (UHNET, MST, and Bruce-TM) were determined using a one-way repeated measures ANOVA. Pearson correlations and liner regression were performed to determine the relationship between the estimated and actual VO2, as well as, determine how well the estimated VO2 predicted the actual VO2. RESULTS: For the Bruce protocol, HRmax=192±10.1bpm; RER=1.2±0.1, and TM=11.29±1.5 min. For the MST, the average HR was 144±23.3bpm. The actual VO2 (46.3±9.4 ml•kg-1•min -1) was similar to the estimated VO2 from UHNET (45.7±5.6 ml•kg-1•min-1) (p=.67) and MST (47.7±10.1 ml•kg-1•min-1) (p=.32). However, the VO2 obtained from the Bruce-TM (42.3±6.7 ml•kg-1•min-1) was significantly lower (p2 . Significant correlations (p2 and all predicted VO2 values. Liner regression equations expressed an R2 of .38, .61, and .65 for UHNET, MST, and Bruce-TM, respectively. CONCLUSION: Bruce-TM provided the most accurate estimation of the actual VO2max. The MST was slightly less predictive of VO2max though still a valid predictor. The results of this study suggest that to accurately predict VO2max, individuals will need to achieve max effort but might not need to have EGs analyzed. The MST results suggest that estimating VO2max on individuals who do not achieve max effort is still a valid option though might not be as accurate as when achieving max effort. These results should be taken with caution. This study was limited by 1) a small sample size, 2) evaluated only 2 modes of exercise, 3) a potential bias due to non-randomized trials, and 4) evaluated only healthy, active individuals. Increasing the sample size, comparing more methodologies, and randomizing the trials could strengthen the validity of any future investigations.



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