Reliability of Gas Exchange Thresholds During a Treadmill Walking Ramp Protocol

The main purpose of the present study was to evaluate the validity and reliability of a novel walking ramp incremental treadmill protocol in sedentary individuals via assessment of the V̇O₂ linear response and plateau phenomenon, in addition to the test-retest reliability of the gas exchange threshold (GET), respiratory compensation point (RCP), and maximum oxygen consumption (V̇O_2max). Fifteen healthy sedentary adults between the ages of 20 – 45 years old performed a waking ramp protocol designed to attain V̇O_2max in 8-12 min using a combination of simultaneous increases in both speed and gradient. Pulmonary gas exchange variables and ventilatory responses were measured using breath-by-breath data and the reliability of measured data was analyzed using intraclass correlation coefficient, coefficient of variation and Bland-Altman plots. The results showed a linear increase in oxygen uptake responses up to V̇O_2max with presence of V̇O₂ plateau in 23 out of 28 tests (82%). There were excellent intra-class correlation coefficients (ICC) in V̇O₂ at GET (ICC = 0.98), RCP (ICC = 0.99) and V̇O_2max (ICC = 0.98), while heart rate showed moderate to good reliability at GET (ICC = 0.84) RCP (ICC = 0.51) and V̇O_2max (ICC = 0.60). Ventilation (V̇E) showed moderate to good ICC at GET (ICC = 0.93), RCP (ICC = 0.51) and V̇O_2max (ICC = 0.65). In conclusion, an individualized walking ramp treadmill protocol showed to be a reliable tool for estimating V̇O_2max and gas exchange thresholds in sedentary individuals. This test provides accurate guidelines for designing a personalized exercise intensity that match the individual capabilities and goals.