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  • Title: Moderate-Intensity Oxygen Uptake Kinetics: Is a Mono-Exponential Function Always Appropriate to Model the Response?
    Author: Dale J, Glaister M.
    Journal: Res Q Exerc Sport; 2018 Sep; 89(3):309-321. PubMed ID: 30071182.
    Abstract:
    PURPOSE: This study investigated the existence of the oxygen uptake ([Formula: see text]) overshoot and the effects of exercise intensity and fitness status on the [Formula: see text] response during moderate-intensity exercise. METHODS: Twelve "high-fitness" (Mage = 26 ± 5 years; Mheight = 184.1 ± 5.4 cm; Mbody mass = 76.6 ± 8.9 kg; mean peak oxygen uptake ([Formula: see text]peak) = 59.0 ± 3.3 mL·kg-1·min·-1) and 11 "moderate-fitness" (Mage = 29 ± 5 years; Mheight = 178.7 ± 7.5 cm; Mbody mass = 81.7 ± 10.9 kg; MV̇O2peak = 45.2 ± 3.1 mL·kg-1·min·-1) participants performed square-wave transitions from unloaded cycling to 3 different intensities (70%, 82.5%, and 95% of the gas exchange threshold). The data were modeled using both a mono-exponential function (Model 1) and a function that included a switch-on component (Model 2). The overshoot was computed by subtracting the steady state from the peak of the modeled response and by calculating the area of the curve that was above steady state. RESULTS: The goodness of fit was affected by model type (p = .002) and exercise intensity (p < .001). High-fitness participants displayed a smaller τ (p < .05) and a larger amplitude (p < .05) and were more likely to overshoot the steady state (p = .035). However, while exercise intensity did affect the amplitude (p < .001), it did not affect τ (p ≥ .05) or the likelihood of an overshoot occurring (p = .389). CONCLUSION: While exercise intensity did not alter the [Formula: see text] response, fitness status affected τ and the likelihood of an overshoot occurring. The overshoot questions the traditional approach to modeling moderate-intensity [Formula: see text] data.
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