PMID 38380301

Research
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Sex Differences in Heart Rate Variability and Vascular Function Following High-Intensity Interval Training in Young Adults

Seo MW, Park TY, Jung H

Question

Do physically active young adult males and females differ in heart-rate variability and vascular function responses after a single bout of cycling HIIT?

Summary

This acute laboratory study compared how healthy physically active young men and women responded during recovery from a single cycling HIIT session. Participants completed 10 rounds of 20 seconds hard cycling at 115-130% Wmax with 100 seconds recovery, after a 5-minute warm-up. Heart-rate variability recovered more slowly in women than men during the first 15 minutes after HIIT, while blood pressure and brachial-ankle pulse wave velocity responses did not differ significantly by sex.

Methodology

  • Healthy physically active young adults, 12 male and 12 female.
  • 24 participants.
  • Cycle ergometer.
  • Work intervals: 20 seconds at 115-130% Wmax.
  • Recovery: 100 seconds at 60 RPM without resistance.
  • Intensity: 115-130% Wmax; applied resistance reported as 3 kp for males and 2 kp for females.
  • 20-minute HIIT program, after at least 5 minutes warm-up.
  • Single acute session.
  • One session.
  • Acute repeated-measures comparison of male and female participants after a single supervised HIIT session.
  • Heart-rate variability, Blood pressure, Brachial-ankle pulse wave velocity, and Body composition were tracked.

Outcomes

HRV time-domain recovery

Male participants recovered faster than female participants for R-R interval, rMSSD, and SDNN by 15 minutes after HIIT.

Sex-by-time interactions were significant for HR, R-R interval, rMSSD, and SDNN; females had lower rMSSD and SDNN than males at 15 minutes after HIIT (p < 0.05).

Mixed

HRV frequency-domain response

Females showed higher LF/HF immediately after HIIT, while males had higher LF/HF at baseline; LF and HF values differed between sexes immediately and 15 minutes after exercise.

Significant sex-by-time interactions were reported for ln LF, ln HF, and ln LF/HF; immediate post-exercise LF/HF was higher in females than males (Cohen's d = 0.98, p < 0.05).

Mixed

Blood pressure and arterial stiffness

No significant sex-by-time interactions were observed for bilateral blood pressure or brachial-ankle pulse wave velocity variables.

The article reports no significant interactions between sexes by time for all blood pressure and ba-PWV variables.

No clear change

Insights

  • Short-interval cycling HIIT can acutely perturb HRV for at least 15 minutes, and recovery patterns may differ by sex in young active adults.
  • Blood pressure and arterial stiffness responses to this single session did not show sex-specific differences.
  • This paper is more useful for recovery monitoring and physiology context than for claims about long-term HIIT training benefits.

Limitations

  • Small sample size.
  • Acute-only design with one HIIT session.
  • No randomization and no non-exercise control group.
  • Only healthy, normal-BMI, physically active young adults were studied.
  • Sex hormones and other biochemical variables were not measured.

Safety

  • Adverse events were not explicitly reported in the the paper.
  • Participants were screened healthy young adults with normal BMI and no disease, medication, or musculoskeletal injury history.
  • A certified strength and conditioning specialist supervised all HIIT procedures.