Question

You are working on a research project and you are looking to collect VO2max measures on obese adults (categorized as such based on weight and BMI). Which method/GXT would you choose to assess CRF and why? Be detailed and specific when explaining/defending your choice

Answer 1

Researchers analyse that relative VO2 max is actually inversely proportional to fat mass -- that is, the more body fat you have, the lower your relative VO2 max. In fact, fat mass is a better predictor of relative VO2 max than exercise performance.

The study is to determine whether adiposity affects the attainment of VO2max. Sixty-seven male and 68 female overweight (body mass index (BMI) = 25-29.9 kg.m) and obese (BMI > or = 30 kg x m) participants undertook a graded treadmill test to volitional exhaustion (phase 1) followed by a verification test (phase 2) to determine the proportion who could achieve a plateau in VO2 and other "maximal" markers (RER, lactate, HR, RPE). At the end of phase 1, 46% of the participants reached a plateau in VO2, 83% increased HR to within 11 beats of age-predicted maximum, 89% reached an RER of > or = 1.15, 70% reached a blood lactate concentration of > or = 8 mmol x L, and 74% reached an RPE of > or = 18. No significant differences between genders and between BMI groups were found with the exception of blood lactate concentration (males = 84% vs females = 56%, P < 0.05). Neither gender nor fatness predicted the number of other markers attained, and attainment of other markers did not differentiate whether a VO2 plateau was achieved. The verification test (phase 2) revealed that an additional 52 individuals (39%) who did not exhibit a plateau in VO2 in phase 1 had no further increase in VO2 in phase 2 despite an increase in workload. These findings indicate that the absence of a plateau in VO2 alone is not indicative of a failure to reach a true maximalVO2 and that individuals with excessive body fat are no less likely than "normal-weight" individuals to exhibit a plateau in VO2 provided that the protocol is appropriate and encouragement to exercise to maximal exertion is provided.

To determine the trustworthiness of graded exercise test to exhaustion (GXT) to assess maximal oxygen uptake (V̇O2 max) in metabolic syndrome individuals with obesity and poor cardiorespiratory fitness. Methods: V̇O2 max was assessed in 100 metabolic syndrome adults (57±8 years; 34% women), with obesity (BMI 32±5 kg·m-2 ) using GXT followed by supramaximal constant-load verification test (VerT) at 110% of maximal GXT work rate. V̇O2 data from GXT and VerT were compared using paired T-test and plotted for Bland-Altman analysis. GXT sensitivity and specificity to detect V̇O2 max were also calculated. Results: 70 individuals did not achieve V̇O2 plateau during GXT. GXT underestimated V̇O2 max in 40 subjects. In these subjects, the magnitude of V̇O2 max underestimation with GXT was 9% (167 mLO2 ·min-1 ; P<0.001). In the whole sample (n=100), bias error differences between GXT and VerT was 63 mLO2 ·min-1 (3% underestimation). This error was constant regardless of differences in fitness levels among individuals (R=-0.07; homoscedasticity). GXT results were unreliable in 62% of the sample with 16% of false positive and 46% of false negative results. Sensitivity and specificity of GTX to assess V̇O2 max were low (i.e., 23 and 60%, respectively). Conclusion: Our data indicates that the magnitude (3-9%) and prevalence (40% of subjects) of V̇O2 max underestimation with the use of a GXT alone is high in a large sample of unfit metabolic syndrome individuals with obesity. Our data advocate for the need of using VerT after GXT to avoid significant cardiorespiratory fitness underestimation in metabolic syndrome individuals with obesity and an already low fitness level.

CONCLUSION
Increase in the BMI affects the physical fitness and causes decrease in the VO2 max. There is a negative association between BMI and VO2 max. Measuring VO2 max by the NASA/Johnson space central physical activity rating (PA-R) scale is useful in knowing physical fitness of individuals in large scale studies. Lifestyle modification should be adopted in medical students to improve their fitness level and hence their work performance.