Can a Supramaximal Treadmill Test be Used to Verify Maximal Oxygen Uptake in
Obese Children?

Background: Children with obesity usually do not reach a plateau during a maximal incremental exercise test. Therefore, we proposed using a supramaximal exercise test (SMT) to verify that the peak oxygen uptake achieved in an incremental exercise test reflects the “true” maximal oxygen uptake (VO2max), in the absence of a VO2 plateau.

Methods: Sixty obese (BMI percentile 95), children (36 females), 10.6±2.7 years old, completed a two-test protocol that included a maximal incremental test (modified Bruce) to exhaustion, followed 10 minutes later by a 2-minute supramaximal constant-load SMT on a treadmill, one stage higher than the last load achieved in the incremental test. Oxygen consumption (VO2), respiratory exchange ratio (RER), percentage of predicted maximal heart rate (%HRp) and rate of perceived exertion (RPE) were recorded at the end of the incremental test and the SMT. VO2max from the incremental test was considered verified by the SMT if peak VO2 in the SMT was 5% higher than the VO2 peak attained in the incremental test.

Results: In 23% of the children VO2 in the SMT was higher than in the incremental test, and VO2max was not verified. There were no significant differences in secondary objective criteria (RER≥1.05, %HRp≥90, and RPE ≥9) between those who had a higher VO2max in the SMT and those verified for VO2 max (RER p=0.16; %HRp p=0.54; RPE p=0.48).

Conclusions: The SMT verified the VO2max determined by the incremental test in 77% of the obese children tested, even in the absence of a plateau phase. For the remaining 23%, VO2max was underestimated by the maximal incremental test. Secondary objective criteria on the incremental test failed to verifyVO2 max. These findings highlight the importance of incorporating an SMT to verify VO2max in this population.