PMID 36232163

Research
All papers

Effects of high-intensity interval training and sprint interval training on cardiac autonomic modulation and cardiorespiratory fitness in healthy women

Oliveira J, Gentil P, Naves JP, Souza Filho LF, Silva L, Zamunér AR, de Lira CA, Rebelo A

Question

Do 8 weeks of HIIT and SIT differ in effects on cardiac autonomic modulation, heart-rate kinetics, and cardiorespiratory fitness in healthy women?

Summary

In healthy physically active women, 8 weeks of supervised cycling HIIT or SIT improved cardiorespiratory conditioning and several heart-rate-variability measures. Traditional HRV and VO2 outcomes did not show a clear overall group-by-time advantage, but nonlinear HRV indices suggested better sympathovagal balance after the higher-volume HIIT protocol.

Methodology

  • Healthy physically active women randomized to HIIT or SIT.
  • 59 participants.
  • Cycle ergometer.
  • Work intervals: 4 minutes.
  • Recovery: 3 minutes active recovery.
  • Intensity: 90-95% HRpeak/critical frequency for work bouts; 50-60% HRpeak during active recovery.
  • About 33 minutes including warm-up.
  • 3 sessions per week.
  • 8 weeks; 24 sessions.
  • Randomized clinical trial
  • VO2, Heart-rate variability, Heart-rate kinetics, and Adherence and safety were tracked.

Outcomes

VO2

VO2 improved over time across groups.

VO2 time effect F=8.993, p=0.004; group effect F=12.523, p=0.001; no significant group x time interaction reported for usual VO2 variables.

Improved

Traditional HRV

Several traditional HRV measures improved over time across groups.

Time effects: RMSSD p=0.002, SDNN p=0.003, SD1 p=0.003, SD2 p=0.011; effects remained after VO2peak adjustment.

Improved

Nonlinear HRV

Nonlinear HRV interactions favored HIIT on selected indices.

Group x time: ES F=6.87, p=0.011; EC F=5.42, p=0.023; 2LV p=0.026; HIIT better than SIT at post for 0V p=0.022, ES p=0.004, EC p=0.025.

Mixed

Retention

A substantial minority of randomized participants abandoned the study.

43 of 59 randomized participants completed; 16 abandoned due to health problems n=2, time availability n=9, and no reason n=5.

Mixed

Insights

  • Both 4x4-minute HIIT and 4x30-second SIT cycling formats can improve fitness/autonomic outcomes in healthy women.
  • Higher-volume HIIT may be more favorable for selected nonlinear HRV markers than lower-volume SIT.
  • Time availability was the largest abandonment reason, so session length and scheduling matter.

Limitations

  • Final analyzed sample was 43 after 16 abandonments.
  • Healthy physically active women only.
  • No non-exercise control group.
  • Adverse events were monitored but not clearly summarized in results.
  • Authors called for probabilistic sampling and other populations.

Safety

  • The protocol included monitoring for dizziness, nausea, muscle pain, and other adverse events.
  • Sixteen participants abandoned the study; two cited health problems.
  • No detailed adverse-event summary was identified in the results sections extracted.