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ORIGINAL RESEARCH article

Front. Physiol.
Sec. Exercise Physiology
Volume 16 - 2025 | doi: 10.3389/fphys.2025.1484722
This article is part of the Research Topic Precision Exercise Prescription: Data-Driven Strategies for Neuromuscular and Cardiovascular Training Across Athletes, Healthy Individuals and Chronic Disease Populations View all 6 articles

Effect of Self-Paced Sprint Interval Training (SIT) and Low-Volume HIIT (LV-HIIT) on Cardiorespiratory Fitness: The Role of Heart Rate and Power Output

Provisionally accepted
Katie Louise Hesketh Katie Louise Hesketh 1,2Sam O Shepherd Sam O Shepherd 2Anton J M Wagenmakers Anton J M Wagenmakers 2Matthew Cocks Matthew Cocks 2Juliette Strauss Juliette Strauss 2*
  • 1 University of Birmingham, Birmingham, England, United Kingdom
  • 2 Liverpool John Moores University, Liverpool, United Kingdom

The final, formatted version of the article will be published soon.

    The primary aim was to assess the efficacy of self-paced sprint interval training (SIT) with lowvolume high-intensity interval training (LV-HIIT) when performed without encouragement on improving cardiorespiratory fitness (CRF). A secondary aim was to explore whether the effort exerted during protocols (power output (PO) and heart rate (HR)) influenced the change in CRF.In a randomised cross-over design, 82 previously inactive adults (m/f: 26/56, 28±10 y, BMI 25±3 kg.m -2 ) undertook 6-weeks of self-paced SIT (4-8x30 s with 120 s recovery) or LV-HIIT (6-10x1 min with 1 min recovery) separated by a 4-week washout period. Sessions were completed 3x/week using WattBikes, and a target of >80% HRmax was suggested during the intervals. Markers of cardio-metabolic health were assessed before and after each intervention. Training increased VO2peak (SIT +3.1±0.4 mL⋅kg -1 ⋅min -1 , LV-HIIT +2.7±1.2 mL⋅kg -1 ⋅min -1 , P<0.001) and decreased body fat % (P=0.002), aortic pulse wave velocity (P=0.002) and glucose tolerance 120 min following an oral glucose tolerance test (P=0.024), with no difference between protocols (P>0.05). When grouping participants into tertiles based on HR and PO responses (n=27), those achieving a low HR had similar changes in VO2peak compared to the high HR group in both interventions (P>0.05). For LV-HIIT, participants in the highest tertile for peak PO had a greater change in VO2peak compared to all other participants (Low 1.8±4.1 mL⋅kg -1 ⋅min -1 , Medium 1.9±3.3 mL⋅kg -1 ⋅min -1 , High 4.3±3.6 ml.kg -1 .min -1 , P=0.020). Six-weeks of self-paced SIT and LV-HIIT induce comparable improvements in CRF, body composition, arterial stiffness and glucose tolerance. Importantly, higher HR did not elicit superior changes in CRF, but PO achieved during LV-HIIT may influence improvements.

    Keywords: High-intensity interval training, cardiorespiratory fitness, self-paced, Real-world, Heart Rate

    Received: 22 Aug 2024; Accepted: 07 Jan 2025.

    Copyright: © 2025 Hesketh, Shepherd, Wagenmakers, Cocks and Strauss. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Juliette Strauss, Liverpool John Moores University, Liverpool, United Kingdom

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.