Abstract
Introduction
The dynamic response of pulmonary oxygen uptake (τV̇O2) during transitions to moderate-intensity exercise is slowed in type 2 diabetes (T2D), partly owing to an impaired blood flow delivery to the active musculature [1]. A prior heavy-intensity warm-up or priming exercise (PE) bout accelerates τV̇O2p in T2D by an enhanced matching of O2 delivery to utilisation [2]. Given both
low-volume, high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) also accelerate τV̇O2 in T2D by similar mechanisms [3], the aim of this study was to assess the priming effects on the V̇O2 and muscle deoxygenation (i.e., deoxygenated haemoglobin and myoglobin, [HHb+Mb]) kinetics during moderate-intensity cycling before training and at weeks 3, 6, 9 and 12 of MICT and HIIT.
Methods
Individuals with T2D (mean ± SD: age 53 ± 10 yr, body mass index 29.8 ± 4.4 kg.m-2) were randomly assigned to MICT (n=10, 50 min of moderate-intensity cycling) or HIIT (n=9, 10 x 1 min cycling at high-intensity interspersed by 1 min of ‘unloaded’ cycling) or to a non-exercising control (CON) group (n=9). Exercising groups trained 3 times/week and every 3 weeks exercise intensity was adjusted. At each time point participants completed four transitions to moderate-intensity cycling. Two of these bouts were completed without priming exercise and two bouts were undertaken with prior high-intensity priming exercise. [HHb+Mb] kinetics were measured by near-infrared spectroscopy at the vastus lateralis muscle. The local matching of O2 delivery to O2 utilisation was assessed by the Δ[HHb+Mb]/ΔV̇ O2 ratio (20-120s). Time point analysis of V̇ O2 and [HHb+Mb] responses were
performed using a two-way ANOVA with repeated-measures, and post-hoc Tukey tests performed when significant differences were returned.
Results
At week 0, PE significantly (P<0.05) reduced τV̇O2 in all 3 groups, (MICT: from 44 ± 12 to 32 ± 5 s; HIIT: from 42 ± 8 to 32 ± 4 s; CON from 43 ± 7 to 31 ± 5 s). However, after 3 weeks of both HIIT and MICT, PE no longer had an effect on τV̇O2, but continued to significantly (P<0.05) reduce τV̇O2 in the CON group. The dynamic response of muscle deoxygenation was not affected by PE or training. Consequently, the Δ[HHb + Mb]/ΔV̇O2 ratio was significantly (P<0.05)reduced with PE at week 0 in all 3 groups, but while this PE-induced reduction was maintained at all time points in the CON group, it was not apparent (P>0.05) beyond the third week of the intervention in the exercising groups.
Conclusion
The accelerated V̇O2 kinetics responses consequent to both MICT and HIIT in T2D were likely attributed to rapid training-adaptations facilitating a better matching of O2 delivery to utilisation, and as such, beyond the third week of training the priming effect was negated.
The dynamic response of pulmonary oxygen uptake (τV̇O2) during transitions to moderate-intensity exercise is slowed in type 2 diabetes (T2D), partly owing to an impaired blood flow delivery to the active musculature [1]. A prior heavy-intensity warm-up or priming exercise (PE) bout accelerates τV̇O2p in T2D by an enhanced matching of O2 delivery to utilisation [2]. Given both
low-volume, high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) also accelerate τV̇O2 in T2D by similar mechanisms [3], the aim of this study was to assess the priming effects on the V̇O2 and muscle deoxygenation (i.e., deoxygenated haemoglobin and myoglobin, [HHb+Mb]) kinetics during moderate-intensity cycling before training and at weeks 3, 6, 9 and 12 of MICT and HIIT.
Methods
Individuals with T2D (mean ± SD: age 53 ± 10 yr, body mass index 29.8 ± 4.4 kg.m-2) were randomly assigned to MICT (n=10, 50 min of moderate-intensity cycling) or HIIT (n=9, 10 x 1 min cycling at high-intensity interspersed by 1 min of ‘unloaded’ cycling) or to a non-exercising control (CON) group (n=9). Exercising groups trained 3 times/week and every 3 weeks exercise intensity was adjusted. At each time point participants completed four transitions to moderate-intensity cycling. Two of these bouts were completed without priming exercise and two bouts were undertaken with prior high-intensity priming exercise. [HHb+Mb] kinetics were measured by near-infrared spectroscopy at the vastus lateralis muscle. The local matching of O2 delivery to O2 utilisation was assessed by the Δ[HHb+Mb]/ΔV̇ O2 ratio (20-120s). Time point analysis of V̇ O2 and [HHb+Mb] responses were
performed using a two-way ANOVA with repeated-measures, and post-hoc Tukey tests performed when significant differences were returned.
Results
At week 0, PE significantly (P<0.05) reduced τV̇O2 in all 3 groups, (MICT: from 44 ± 12 to 32 ± 5 s; HIIT: from 42 ± 8 to 32 ± 4 s; CON from 43 ± 7 to 31 ± 5 s). However, after 3 weeks of both HIIT and MICT, PE no longer had an effect on τV̇O2, but continued to significantly (P<0.05) reduce τV̇O2 in the CON group. The dynamic response of muscle deoxygenation was not affected by PE or training. Consequently, the Δ[HHb + Mb]/ΔV̇O2 ratio was significantly (P<0.05)reduced with PE at week 0 in all 3 groups, but while this PE-induced reduction was maintained at all time points in the CON group, it was not apparent (P>0.05) beyond the third week of the intervention in the exercising groups.
Conclusion
The accelerated V̇O2 kinetics responses consequent to both MICT and HIIT in T2D were likely attributed to rapid training-adaptations facilitating a better matching of O2 delivery to utilisation, and as such, beyond the third week of training the priming effect was negated.
| Original language | English |
|---|---|
| Article number | A 03-18 |
| Pages (from-to) | 376-377 |
| Number of pages | 2 |
| Journal | Acta Physiologica |
| Volume | 236 |
| Issue number | S725 |
| Early online date | 12 Sept 2022 |
| DOIs | |
| Publication status | Published - 30 Sept 2022 |
| Event | Europhysiology 2022 - Tivoli Congress Center, Copenhagen, Denmark Duration: 16 Sept 2022 → 18 Sept 2022 https://www.physoc.org/events/europhysiology-2022/ |
