The oxygen uptake efficiency slope reflects exercise-training induced changes in VO2max in obese children

Katrin A. Dias, Concetta E. Masterson, Matthew Wallen, Charlotte B. Ingul, Peter Davies, Gary Leong, Peter A. Cain, Ross Arena, Jeff Coombes

Research output: Contribution to journalMeeting Abstractpeer-review


An improvement in cardiorespiratory fitness (CRF) following an exercise intervention is a primary indicator of training efficacy. In obese children, maximal oxygen uptake (VO2max) may not be achieved during an exercise test due to reduced motivation or peripheral fatigue. Identifying a valid surrogate for VO2max, obtained with a submaximal exercise effort, would therefore be advantageous in this population.

PURPOSE: To determine whether exercise-training induced changes in VO2max are associated with changes in a submaximal six-minute oxygen uptake efficiency slope (6minOUES) protocol in obese children.

METHODS: Sixty-three obese children (BMI>95th percentile for age & sex) completed a maximal exercise treadmill test with ventilatory expired gas analysis before and after a three-month exercise intervention. Participants who satisfied oxygen uptake plateau criteria and achieved a peak respiratory exchange ratio (RER) ≥1.05 were classified as reaching VO2max. Thirteen participants (age 13.0±2.0; Tanner puberty stage 3 (2.5-4.5), female 69%) reached VO2max prior to and following the intervention and were included in this analysis. The OUES was determined as the slope of the line when VO2 (ml/min) was plotted against logVE. Maximal OUES (OUESmax) was calculated from start to end of the test while 6minOUES was calculated from start of the test to the 6-minute marker. Body fat percentage was quantified using dual x-ray absorptiometry or air displacement plethysmography. VO2max, OUESmax and 6minOUES were normalised to body weight and change scores were calculated.

RESULTS: There was an increase in VO2max of 2.85±5.48 ml/kg/min following a three-month exercise intervention. This was closely reflected by a mean increase in OUESmax (3.45±7.60) and 6minOUES (3.62±8.49). The increase in VO2max was strongly correlated with an increase in OUESmax (r2 = 0.81, p<0.05) and an increase in 6minOUES (r2 = 0.77, p<0.05) independent of sex and change in percent body fat. The increase in 6minOUES was strongly correlated with the increase in OUESmax (r2 = 0.91, p<0.05).

CONCLUSION: The 6minOUES treadmill protocol is a valid submaximal measure of exercise-training induced CRF changes in obese children. This may be valuable when VO2max is not achieved in exercise testing designed to determine training-induced improvements.
Original languageEnglish
Article number3676
Pages (from-to)1024
Number of pages1
JournalMedicine and Science in Sports and Exercise
Issue number5S
Publication statusPublished - May 2016
Externally publishedYes


  • obesity
  • child obesity
  • exercise programs
  • oxygen uptake


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