Time course of changes in V̇O2peak and O2 extraction during ramp cycle exercise following HIIT vs moderate-intensity continuous training in type 2 diabetes

Norita Gildea, Adam McDermott, Joel Rocha, Donal O'Shea, Simon Green, Mikel Egaña*

*Corresponding author for this work

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In the present study we assessed the time course of adaptations in peak oxygen uptake (V̇O2peak) and muscle fractional oxygen (O2) extraction (using near-infrared spectroscopy) following 12 weeks of low-volume high-intensity interval training (HIIT) vs. moderate-intensity continuous endurance training (MICT) in adults with uncomplicated type 2 diabetes (T2D). Participants with T2D were randomly assigned to MICT (n = 12, 50 min of moderate-intensity cycling), HIIT (n = 9, 10 x 1 min at ~90% maximal heart rate) or to a non-exercising control group (n = 9). Exercising groups trained 3 times per week and measurements were taken every 3 weeks. The rate of muscle deoxygenation (i.e. deoxygenated haemoglobin and myoglobin concentration, Δ[HHb+Mb]) profiles of the vastus lateralis muscle were normalised to 100% of the response, plotted against % power output (PO) and fitted with a double linear regression model. V̇O2peak increased (P<0.05) by week 3 of MICT (+17%) and HIIT (+8%), with no further significant changes thereafter. Total increases in V̇O2peak posttraining (P<0.05) were 27% and 14% respectively. The %∆[HHb+Mb] vs %PO slope of the first linear segment (slope1) was reduced (P<0.05) beyond 3 weeks of HIIT and MICT with no further significant changes thereafter. No changes in V̇O2peak or slope1 were observed in the control group. Low-volume HIIT and MICT induced improvements in V̇O2peak following a similar time course and these improvements were likely, at least in part, due to an improved microvascular O2 delivery.
Original languageEnglish
JournalAmerican Journal of Physiology
Early online date24 Feb 2021
Publication statusE-pub ahead of print - 24 Feb 2021

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