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. 2023 Jul 11;15(1):83.
doi: 10.1186/s13102-023-00682-8.

Impact of high intensity interval exercise with and without heat stress on cardiovascular and aerobic performance: a pilot study

Alexs A Matias  1   2 , Isabelle F Albin  1 , Leah Glickman  1 , Peter A Califano  1 , Justin M Faller  1 , Gwenael Layec  2   3 , Stephen J Ives  4
Affiliations

Impact of high intensity interval exercise with and without heat stress on cardiovascular and aerobic performance: a pilot study

Alexs A Matias et al. BMC Sports Sci Med Rehabil. .

Abstract

Background: Heat stress during aerobic exercise training may offer an additional stimulus to improve cardiovascular function and performance in a cool-temperate environment. However, there is a paucity of information on the additive effects of high-intensity interval exercise (HIIE) and acute heat stress. We aimed to determine the effects of HIIE in combination with acute heat stress on cardiovascular function and exercise performance.

Methods: Twelve active (peak O2 consumption [VO2peak]: 47 ± 8 ml·O2/min/kg) young adults were counterbalanced to six sessions of HIIE in hot (HIIE-H, 30 ± 1 °C, 50 ± 5% relative humidity [RH]) or temperate conditions (HIIE-T, 20 ± 2 °C, 15 ± 10% RH). Resting heart rate (HR), HR variability (HRV), central (cBP) and peripheral blood pressure (pBP), peripheral mean arterial pressure (pMAP), pulse wave velocity (PWV), VO2peak, and 5-km treadmill time-trial were measured pre- and post-training.

Results: Resting HR and HRV were not significantly different between groups. However, expressed as percent change from baseline, cSBP (HIIE-T: + 0.9 ± 3.6 and HIIE-H: -6.6 ± 3.0%, p = 0.03) and pSBP (HIIE-T: -2.0 ± 4.6 and HIIE-H: -8.4 ± 4.7%, p = 0.04) were lower in the heat group. Post-training PWV was also significantly lower in the heat group (HIIE-T: + 0.4% and HIIE-H: -6.3%, p = 0.03). Time-trial performance improved with training when data from both groups were pooled, and estimated VO2peak was not significantly different between groups (HIIE-T: 0.7% and HIIE-H: 6.0%, p = 0.10, Cohen's d = 1.4).

Conclusions: The addition of acute heat stress to HIIE elicited additive adaptations in only cardiovascular function compared to HIIE alone in active young adults in temperate conditions, thus providing evidence for its effectiveness as a strategy to amplify exercise-induced cardiovascular adaptations.

Keywords: Blood pressure; Heat acclimation; Pulse wave velocity; Running; Vascular stiffness.

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Conflict of interest statement

The authors declare they have no competing interests.

Figures

Fig. 1
Fig. 1
Schematic of the experimental design, detailing the different visits, timing between visits, and tests being conducted (and the order of tests)
Fig. 2
Fig. 2
A Peripheral Diastolic Blood Pressure (pDBP; Cohen’s d = 0.7) and (C) Central Diastolic Blood Pressure (cDBP; Cohen’s d = 0.5) at baseline and post-HIIE training with or without heat acclimation; B percent change in pDBP (Cohen’s d = 0.9) and (D) cDBP (Cohen’s d = 0.7). HIIE-T (n = 5; females = 3, males = 2) and HIIE-H (n = 5; females = 3, males = 2). Data presented mean ± SEM
Fig. 3
Fig. 3
A Peripheral Systolic Blood Pressure (pSBP; Cohen’s d = 2.5) and (C) Central Systolic Blood Pressure (cSBP; Cohen’s d = 1.2) at baseline and post-HIIE training with or without heat acclimation; B percent change in pSBP (Cohen’s d = 1.5) and (D) cSBP (Cohen’s d = 1.6). HIIE-T (n = 5; females = 3, males = 2) and HIIE-H (n = 5; females = 3, males = 2). *p < 0.05. **p < 0.001. A one-tailed Mann–Whitney U Test was used to identify group differences in relative changes from baseline (panel B and D). Repeated measures 2 × 2 ANOVA was used to identify any potential main effects and interactions (panel A and C). Data presented mean ± SEM
Fig. 4
Fig. 4
A Mean Arterial Pressure at baseline and post-HIIE training with or without heat acclimation (Cohen’s d = 1.2); B percent change in MAP (Cohen’s d = 1.5). HIIE-T (n = 5; females = 3, males = 2) and HIIE-H (n = 5; females = 3, males = 2). A one-tailed Mann–Whitney U Test was used to identify any potential group differences in relative changes from baseline (panel B). Data presented mean ± SEM
Fig. 5
Fig. 5
A Pulse Wave velocity (PWV) at baseline and post-HIIE training with or without heat acclimation (Cohen’s d = 1.6); B percent change in PWV (Cohen’s d = 1.5). HIIE-T (n = 5; females = 3, males = 2) and HIIE-H (n = 5; females = 3, males = 2). *p < 0.05. A one-tailed Mann–Whitney U Test was used to identify group differences in relative changes from baseline (panel B). Repeated measures 2 × 2 ANOVA was used to identify any potential main effects and interactions (panel A). Data presented mean ± SEM
Fig. 6
Fig. 6
A Peak oxygen consumption (VO2peak; Cohen’s d = 0.3) and C 5 km time-trial duration (Cohen’s d = 0.4) at baseline and post-HIIE training with or without heat acclimation; B percent change in VO2peak (Cohen’s d = 1.2) and (D) 5 km time-trial duration (Cohen’s d = 0.1). The sample size for the heat group is n = 4 for VO2peak absolute and % change in panels A. and B. When the data were pooled (HIIE-T + HIIE-H), there was a trend towards a reduction in 5 km time-trial performance with HIIE training (Pre: 1695 ± 231 vs. Post: 1620 ± 210 s; Cohen’s d = 0.40, p = 0.0511). HIIE-T (n = 5; females = 3, males = 2) and HIIE-H (n = 5; females = 3, males = 2). A one-tailed Mann–Whitney U Test was used to identify group differences in relative changes from baseline (panel B and D). Data presented mean ± SEM
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