Low-volume HIIT and MICT speed V̇o2 kinetics during high-intensity “work-to-work” cycling with a similar time-course in type 2 diabetes

Norita Gildea, Adam McDermott, Joel Rocha, Domenico Crognale, Aaron Nevin, Donal O'Shea, Simon Green, Mikel Egaña (Lead / Corresponding author)

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Abstract

We assessed the rates of adjustment in oxygen uptake (V̇O2) and muscle deoxygenation [i.e., deoxygenated hemoglobin and myoglobin, (HHb + Mb)] during the on-transition to high-intensity cycling initiated from an elevated baseline (work-to-work, w-to-w) before training and at weeks 3, 6, 9, and 12 of low-volume high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) in type 2 diabetes (T2D). Participants were randomly assigned to MICT (n = 11, 50 min of moderate-intensity cycling), HIIT (n = 8, 10 × 1 min of high-intensity cycling separated by 1 min of light cycling) or nonexercising control (n = 9) groups. Exercising groups trained three times per week. Participants completed two w-to-w transitions at each time point consisting of sequential step increments to moderate- and high-intensity work-rates. [HHb + Mb] kinetics were measured by near-infrared spectroscopy at the vastus lateralis muscle. The pretraining time constant of the primary phase of V̇O2 (V̇Oτp) and the amplitude of the V̇Oslow component (V̇OAs) of the high-intensity w-to-w bout decreased (P < 0.05) by a similar magnitude at week 3 of training in both MICT (from 56 ± 9 to 43 ± 6 s, and from 0.17 ± 0.07 to 0.09 ± 0.05 L/min, respectively) and HIIT (from 56 ± 8 to 42 ± 6 s, and from 0.18 ± 0.05 to 0.09 ± 0.08 L/min, respectively) with no further changes thereafter. No changes were reported in controls. The parameter estimates of Δ[HHb + Mb] remained unchanged in all groups. MICT and HIIT elicited comparable improvements in V̇Okinetics without changes in muscle deoxygenation kinetics during high-intensity exercise initiated from an elevated baseline in T2D despite training volume and time commitment being ∼50% lower in the HIIT group.

NEW & NOTEWORTHY Three weeks of high-intensity interval training and moderate-intensity continuous training decreased the time constant of the primary phase of oxygen uptake (V̇O2) and amplitude of the V̇Oslow component during a high-intensity exercise initiated from an elevated baseline, a protocol that mimics the abrupt metabolic transitions akin to those in daily life, in type 2 diabetes. These V̇O2 kinetics improvements were maintained until the end of the 12-wk intervention without changes in muscle deoxygenation kinetics.
Original languageEnglish
Pages (from-to)273-287
Number of pages15
JournalJournal of Applied Physiology
Volume133
Issue number2
Early online date3 Aug 2022
DOIs
Publication statusPublished - Aug 2022

Keywords

  • exercise tolerance
  • exercise transitions
  • near-infrared spectroscopy
  • oxygen extraction
  • oxygen uptake slow component

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