Assessing VO2 Max: Beyond The Metabolic Cart

BACKGROUND: Direct measurement of maximal aerobic capacity (VO2max) requires use of a metabolic cart in a laboratory setting. However, direct measurement of a subject's VO2max has limitations, such that the test cannot be performed in the field, requires technical expertise, and requires exercise to volitional exhaustion. As a result, a submaximal cardiorespiratory test known as the Rockport Walking Test (RWT) was developed, where the needed equipment is a level 1-mile surface, a stopwatch, and a scale to measure body weight. PURPOSE: The aim of this study is to determine the validity and reliability of the RWT (submaximal) compared with the peak speed treadmill running VO2Peak (maximal) test. METHODS: Thirty collegiate students (16 females, 14 males) completed both a RWT and VO2Peak test, on a treadmill, in randomized order conducted one week apart. For the RWT, mile time (self-selected pace on treadmill), heart rate (chest-strap monitor), sex, and weight were entered into the RWT equation to estimate VO2max. For the VO2Peak test, a metabolic cart (ParvoMed TrueOne 2400) measured VO2max using an 8-to-12-minute VO2peak protocol where the intensity of the first stage was an easy walk or jog based on the participant's ability. Then, treadmill speed was increased 0.5 mph every minute until volitional exhaustion. Differences between the RWT and VO2Peak test were calculated using paired-sample t-tests and relationships analyzed using Pearson’s r. Data presented as means±SD with significance set at p < 0.05. RESULTS: VO2max was 3.14 ± 4.7 mL/kg/min higher using the RWT compared with the VO2Peak test. However, the mean differences between the RWT vs. the VO2Peak test were not (statistically) significantly different (40.8 ± 10.1 vs.37.7 ± 9.1 mL/kg/min; p = 0.21). A significant correlation was noted between the RWT vs. VO2Peak test (r = 0.89; p < 0.0001). Males had a higher VO2max test compared with females for both the RWT (45.9 ± 7.7 vs. 36.3 ± 10.0 mL/kg/min; p = 0.007) and VO2Peak test (43.4 ± 7.1 vs. 32.6 ± 7.6 mL/kg/min; p = 0.0005). CONCLUSIONS: The RWT slightly (~3 mL/kg/min), but non-significantly, overestimated VO2max, when compared with the VO2Peak test. Thus, both the RWT (submaximal) and running VO2max (maximal) tests can be used interchangeably when performed on a treadmill for research, clinical, and performance purposes.