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. 2025 Feb;125(2):317-326.
doi: 10.1007/s00421-024-05600-5. Epub 2024 Sep 5.

Physiological and perceptual response to critical power anchored HIIT: a sex comparison study

Lauren J Pacitti  1 , Joshua Laberge  1 , Kaitlyn E Shikaze  1 , Patrick J Drouin  1 , Michael E Tschakovsky  1 , Chris McGlory  1 , Brendon J Gurd  2
Affiliations

Physiological and perceptual response to critical power anchored HIIT: a sex comparison study

Lauren J Pacitti et al. Eur J Appl Physiol. 2025 Feb.

Abstract

Purpose: The aim of this study was to test the hypothesis that using threshold-based high intensity interval training (HIITTHR) prescribed at an intensity above critical power (CP) in males and females matched for maximal oxygen uptake ( V ˙ O2max) (mL/kg lean mass/min) will yield no sex differences in time to fatigue.

Methods: Thirteen males (mean ± SD: 22.0 ± 2.48 years, 181 ± 8.36 cm, 78.8 ± 11.4 kg) and eleven females (mean ± SD: 22.4 ± 2.69 years, 170 ± 5.73 cm, 65.2 ± 7.66 kg) initially undertook an incremental test to exhaustion to determine V ˙ O2max, and a CP test. Then, one HIIT session (4 min on, 2 min off) was performed to exhaustion at the work rate associated with 105%CP. Acute physiological and cardiovascular responses were recorded.

Results: No sex differences were recorded in time to fatigue [Female vs. Male (min): 36.0 ± 18.5 vs. 39.3 ± 16.3], heart rate, rate of perceived exertion, or %oxygenated [haem]. Females displayed lower %deoxygenated [haem] at the end of interval 1, 2, 3, and 4 [Female vs. Male (%): 89.4 ± 21.2 vs. 110 ± 27.3, 92.0 ± 21.5 vs. 115 ± 27.6, 87.1 ± 23.7 vs. 112 ± 22.8, 88.9 ± 26.3 vs. 113 ± 23.5]. Large interindividual variability in performance, and physiological and perceptual response were present despite the use of threshold-based prescription.

Conclusion: The present study suggests that threshold-based prescription may help standardize the mean response exercise across sexes but does not eliminate physiological or perceptual variability. Furthermore, the lack of sex differences in TTF was accompanied by greater %deoxy[haem] in males, indicating tissue oxygenation is an unlikely determinant of HIIT performance. This study has been retrospectively registered at Trial Registration https://doi.org/10.17605/OSF.IO/KZVGC January 17th, 2023, following data collection but prior to data analyses.

Keywords: Critical power; Intermittent exercise; Sex comparison; Threshold-based prescription.

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Conflict of interest statement

Declarations. Conflict of interest: The authors declare no financial or non-financial interests that are directly or indirectly related to the work submitted for publication. Ethical approval: This study was approved by The Health Sciences Human Research Ethics Board at Queen’s University, Kingston, Ontario, Canada (ref. no: 6003260) and conformed to the Declaration of Helsinki. Informed consent: Informed consent was obtained from all individual participants included in this study. The participants consented to the publication of their results.

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