Cardiorespiratory fitness, assessed during cardiopulmonary exercise tests by peak oxygen uptake ( o2pk), is an independent predictor of mortality in obesity. We investigated whether o2pk and systemic responses measured during field walking tests were similar to those measured during an incremental treadmill test (ITMT) in obese individuals with treated OSA.
Individuals with treated OSA and a BMI > 30 kg/m2 were recruited. Participants completed an ITMT, two 6-min walk tests (6MWTs), and two incremental shuttle walk tests (ISWTs) on three separate days in a randomized order. Expired gas analysis was performed during all tests.
The study was completed by 16 patients (nine men) (mean [SD] age, 58  y; BMI, 36.1 [7.6] kg/m2). There was no difference (P = .27) in o2pk assessed by the ITMT and the ISWT (2,266  and 2,017  mL/min, respectively). The o2pk measured by the 6MWT (1,778  mL/min) was lower than that measured by the ITMT (P < .01). The limits of agreement for o2pk between the ISWT and the ITM were ± 730 mL/min. Cardiorespiratory responses during the ISWT and the ITMT reflected a graded response to a peak, whereas the 6MWT demonstrated a rapid rise to a plateau.
The ISWT can be used instead of an ITMT and in preference to the 6MWT to assess cardiorespiratory fitness for a cohort of obese people with treated OSA. However, the imprecision of the agreement in o2pk between the ITMT and ISWT means they cannot be used interchangeably in an individual.
ClinicalTrials.gov; No.: NCT01930513; www.clinicaltrials.gov