Effects of intermittent sprint-based heat acclimation at various pedal resistances on physiological responses during incremental exercise

Callum McGregor; Andrew Marley; John Babraj

doi:10.1007/s42978-024-00324-6

Effects of intermittent sprint-based heat acclimation at various pedal resistances on physiological responses during incremental exercise

Callum McGregor^*
, Andrew Marley
, John Babraj

^*Corresponding author for this work

Department of Health, Sport and Wellbeing

Research output: Contribution to journal › Article › peer-review

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Abstract

Purpose: Standard heat acclimation (HA) protocols (low-moderate intensity over a continuous 7-14 days) restore performance and thermoregulation but lack specificity and practicality for intermittent sports athletes. This study compared different pedal resistances in a 3-week intermittent sprint-based HA protocol.
Methods: Fourteen physically active adults were assigned to a sprint pedal resistance training group (TG): 0.075 kg·kg⁻¹ (7.5TG, 6 males, 1 female) or 0.085 kg·kg⁻¹ (8.5TG, 5 males, 2 females). Participants completed baseline incremental time to exhaustion test (TTE), continued with own training for 3 weeks before post-control TTE, then carried out 6 X 15s cycle sprints with 30s recovery followed by 30min low intensity cycling thrice weekly for 3 weeks before completing post-HA TTE test. Testing and HA were completed at 38°C and 30% relative humidity.
Results: Both groups improved TTE from baseline to post-HA (7.5TG: 9.6±10.8%, 8.5TG: 7.4±3.1%) and post-control to post-HA (7.5TG: 11.0±11.7%, 8.5TG: 6.7±3.9%). Maximal power improved from baseline to post-HA (7.5TG: 293±40 W vs 321±46 W, 8.5TG: 318±90 W vs 339±96 W), while only 7.5TG improved maximal power from post-control to post-HA (289±42 W vs 321±46 W) . From baseline to post-HA and post-control to post-HA, only 7.5TG increased time till maximum skin temperature (460±76 s vs 509±75 s, 461±72 s vs 509±75 s, respectively) and minimum core-skin gradient (461±71 s vs 510±74 s, 455±75 s vs 510±74 s, respectively), while exercising core temperature remained unchanged in both groups. Both groups increased sweat rate (7.5TG: 7.0±3.4 mgs·cm2·min-1 vs 9.6±4.1 mgs·cm2·min-1, 8.5TG: 5.7±3.6 mgs·cm2·min-1 vs 8.3±4.3 mgs·cm2·min-1) . Only 7.5TG delayed onset of blood lactate accumulation from baseline to post-HA (259±126 s vs 354±86 s) .
Conclusion: Intermittent sprint-based HA improves TTE performance and sweat rate while a lighter sprint pedal resistance offers, greater thermal adaptation and fatigue tolerance.

Original language	English
Article number	e13463
Pages (from-to)	54-63
Number of pages	10
Journal	Journal of Science in Sport and Exercise
Volume	8
Issue number	1
Early online date	17 Jan 2025
DOIs	https://doi.org/10.1007/s42978-024-00324-6
Publication status	Published - 1 Feb 2026

Keywords

Heat
Acclimation
SIT
Pedal resistance
Oxygenation

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Babraj_EffectsOfIntermittentSprint-BasedHeat_Published_2025Final published version, 655 KBLicence: CC BY

The effects of heat acclimation on physiological responses to sprint interval training at various pedal resistances
McGregor, C. (Author), Babraj, J. (Supervisor) & Marley, A. (Supervisor), 1 Mar 2024
Student thesis: Masters Thesis › Masters by Research

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title = "Effects of intermittent sprint-based heat acclimation at various pedal resistances on physiological responses during incremental exercise",

abstract = "Purpose: Standard heat acclimation (HA) protocols (low-moderate intensity over a continuous 7-14 days) restore performance and thermoregulation but lack specificity and practicality for intermittent sports athletes. This study compared different pedal resistances in a 3-week intermittent sprint-based HA protocol. Methods: Fourteen physically active adults were assigned to a sprint pedal resistance training group (TG): 0.075 kg·kg⁻¹ (7.5TG, 6 males, 1 female) or 0.085 kg·kg⁻¹ (8.5TG, 5 males, 2 females). Participants completed baseline incremental time to exhaustion test (TTE), continued with own training for 3 weeks before post-control TTE, then carried out 6 X 15s cycle sprints with 30s recovery followed by 30min low intensity cycling thrice weekly for 3 weeks before completing post-HA TTE test. Testing and HA were completed at 38°C and 30\% relative humidity. Results: Both groups improved TTE from baseline to post-HA (7.5TG: 9.6±10.8\%, 8.5TG: 7.4±3.1\%) and post-control to post-HA (7.5TG: 11.0±11.7\%, 8.5TG: 6.7±3.9\%). Maximal power improved from baseline to post-HA (7.5TG: 293±40 W vs 321±46 W, 8.5TG: 318±90 W vs 339±96 W), while only 7.5TG improved maximal power from post-control to post-HA (289±42 W vs 321±46 W) . From baseline to post-HA and post-control to post-HA, only 7.5TG increased time till maximum skin temperature (460±76 s vs 509±75 s, 461±72 s vs 509±75 s, respectively) and minimum core-skin gradient (461±71 s vs 510±74 s, 455±75 s vs 510±74 s, respectively), while exercising core temperature remained unchanged in both groups. Both groups increased sweat rate (7.5TG: 7.0±3.4 mgs·cm2·min-1 vs 9.6±4.1 mgs·cm2·min-1, 8.5TG: 5.7±3.6 mgs·cm2·min-1 vs 8.3±4.3 mgs·cm2·min-1) . Only 7.5TG delayed onset of blood lactate accumulation from baseline to post-HA (259±126 s vs 354±86 s) . Conclusion: Intermittent sprint-based HA improves TTE performance and sweat rate while a lighter sprint pedal resistance offers, greater thermal adaptation and fatigue tolerance.",

author = "Callum McGregor and Andrew Marley and John Babraj",

note = "{\textcopyright} 2025, Crown This is an open access article distributed under the terms of the Creative Commons CC BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Data availability statement: The datasets generated and analysed during this study are available from the corresponding author on reasonable request.",

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T1 - Effects of intermittent sprint-based heat acclimation at various pedal resistances on physiological responses during incremental exercise

AU - McGregor, Callum

AU - Marley, Andrew

AU - Babraj, John

N1 - © 2025, Crown This is an open access article distributed under the terms of the Creative Commons CC BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Data availability statement: The datasets generated and analysed during this study are available from the corresponding author on reasonable request.

PY - 2026/2/1

Y1 - 2026/2/1

N2 - Purpose: Standard heat acclimation (HA) protocols (low-moderate intensity over a continuous 7-14 days) restore performance and thermoregulation but lack specificity and practicality for intermittent sports athletes. This study compared different pedal resistances in a 3-week intermittent sprint-based HA protocol. Methods: Fourteen physically active adults were assigned to a sprint pedal resistance training group (TG): 0.075 kg·kg⁻¹ (7.5TG, 6 males, 1 female) or 0.085 kg·kg⁻¹ (8.5TG, 5 males, 2 females). Participants completed baseline incremental time to exhaustion test (TTE), continued with own training for 3 weeks before post-control TTE, then carried out 6 X 15s cycle sprints with 30s recovery followed by 30min low intensity cycling thrice weekly for 3 weeks before completing post-HA TTE test. Testing and HA were completed at 38°C and 30% relative humidity. Results: Both groups improved TTE from baseline to post-HA (7.5TG: 9.6±10.8%, 8.5TG: 7.4±3.1%) and post-control to post-HA (7.5TG: 11.0±11.7%, 8.5TG: 6.7±3.9%). Maximal power improved from baseline to post-HA (7.5TG: 293±40 W vs 321±46 W, 8.5TG: 318±90 W vs 339±96 W), while only 7.5TG improved maximal power from post-control to post-HA (289±42 W vs 321±46 W) . From baseline to post-HA and post-control to post-HA, only 7.5TG increased time till maximum skin temperature (460±76 s vs 509±75 s, 461±72 s vs 509±75 s, respectively) and minimum core-skin gradient (461±71 s vs 510±74 s, 455±75 s vs 510±74 s, respectively), while exercising core temperature remained unchanged in both groups. Both groups increased sweat rate (7.5TG: 7.0±3.4 mgs·cm2·min-1 vs 9.6±4.1 mgs·cm2·min-1, 8.5TG: 5.7±3.6 mgs·cm2·min-1 vs 8.3±4.3 mgs·cm2·min-1) . Only 7.5TG delayed onset of blood lactate accumulation from baseline to post-HA (259±126 s vs 354±86 s) . Conclusion: Intermittent sprint-based HA improves TTE performance and sweat rate while a lighter sprint pedal resistance offers, greater thermal adaptation and fatigue tolerance.

AB - Purpose: Standard heat acclimation (HA) protocols (low-moderate intensity over a continuous 7-14 days) restore performance and thermoregulation but lack specificity and practicality for intermittent sports athletes. This study compared different pedal resistances in a 3-week intermittent sprint-based HA protocol. Methods: Fourteen physically active adults were assigned to a sprint pedal resistance training group (TG): 0.075 kg·kg⁻¹ (7.5TG, 6 males, 1 female) or 0.085 kg·kg⁻¹ (8.5TG, 5 males, 2 females). Participants completed baseline incremental time to exhaustion test (TTE), continued with own training for 3 weeks before post-control TTE, then carried out 6 X 15s cycle sprints with 30s recovery followed by 30min low intensity cycling thrice weekly for 3 weeks before completing post-HA TTE test. Testing and HA were completed at 38°C and 30% relative humidity. Results: Both groups improved TTE from baseline to post-HA (7.5TG: 9.6±10.8%, 8.5TG: 7.4±3.1%) and post-control to post-HA (7.5TG: 11.0±11.7%, 8.5TG: 6.7±3.9%). Maximal power improved from baseline to post-HA (7.5TG: 293±40 W vs 321±46 W, 8.5TG: 318±90 W vs 339±96 W), while only 7.5TG improved maximal power from post-control to post-HA (289±42 W vs 321±46 W) . From baseline to post-HA and post-control to post-HA, only 7.5TG increased time till maximum skin temperature (460±76 s vs 509±75 s, 461±72 s vs 509±75 s, respectively) and minimum core-skin gradient (461±71 s vs 510±74 s, 455±75 s vs 510±74 s, respectively), while exercising core temperature remained unchanged in both groups. Both groups increased sweat rate (7.5TG: 7.0±3.4 mgs·cm2·min-1 vs 9.6±4.1 mgs·cm2·min-1, 8.5TG: 5.7±3.6 mgs·cm2·min-1 vs 8.3±4.3 mgs·cm2·min-1) . Only 7.5TG delayed onset of blood lactate accumulation from baseline to post-HA (259±126 s vs 354±86 s) . Conclusion: Intermittent sprint-based HA improves TTE performance and sweat rate while a lighter sprint pedal resistance offers, greater thermal adaptation and fatigue tolerance.

U2 - 10.1007/s42978-024-00324-6

DO - 10.1007/s42978-024-00324-6

M3 - Article

SN - 2096-6709

VL - 8

SP - 54

EP - 63

JO - Journal of Science in Sport and Exercise

JF - Journal of Science in Sport and Exercise

IS - 1

M1 - e13463

ER -

Effects of intermittent sprint-based heat acclimation at various pedal resistances on physiological responses during incremental exercise

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The effects of heat acclimation on physiological responses to sprint interval training at various pedal resistances

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