PMID 33481836

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Changes in VO2max and cardiac output in response to short-term high-intensity interval training in Caucasian and Hispanic young women: A pilot study

De Revere JL, Clausen RD, Astorino TA

Question

Does ethnicity alter the change in cardiorespiratory fitness and hemodynamic responses to a low dose of high-intensity interval training in inactive young women?

Summary

This pilot study tested whether three weeks of low-volume supervised cycling HIIT produced different cardiorespiratory adaptations in inactive non-obese Caucasian and Hispanic young women. Both groups improved VO2max by about 8%, with no group-by-training interaction for VO2max. Caucasian women showed significant increases in cardiac output and stroke volume, while Hispanic women appeared to improve more through oxygen extraction, but the study was small and short.

Methodology

  • Healthy inactive non-obese young women, 12 Caucasian and 10 Hispanic completers.
  • 22 participants.
  • Electronically braked cycle ergometer.
  • Work intervals: 60 seconds at 85% peak power output.
  • Recovery: 75 seconds at 10% peak power output.
  • Intensity: 85% peak power output for work; average training peak heart rate 89.8% HRmax.
  • 22 to 26.5 minutes including 4-minute warmup.
  • 3 sessions per week.
  • 3 weeks.
  • Longitudinal repeated-measures between-subjects pilot study comparing Caucasian and Hispanic women before and after the same HIIT intervention.
  • Relative VO2max, Absolute VO2max, Peak power output, and Cardiac output were tracked.

Outcomes

Relative VO2max

Relative VO2max increased from 31.07 +/- 3.74 to 33.70 +/- 3.74 mL/kg/min in Caucasian women and from 28.37 +/- 3.83 to 30.45 +/- 3.64 mL/kg/min in Hispanic women.

Main effect of training F(1,20)=13.97, p=0.001; no group-by-training interaction p=0.65; effect sizes d=1.32 and d=1.04.

Improved

Absolute VO2max

Absolute VO2max increased from 1.89 +/- 0.37 to 2.06 +/- 0.32 L/min in Caucasian women and from 1.71 +/- 0.33 to 1.85 +/- 0.29 L/min in Hispanic women.

Main effect of training F(1,20)=27.29, p<0.001; no group-by-training interaction p=0.66; effect sizes d=1.78 and d=1.48.

Improved

Cardiac output

Cardiac output increased in Caucasian women from 17.82 +/- 2.31 to 19.92 +/- 2.47 L/min but changed little in Hispanic women, from 18.41 +/- 2.42 to 18.52 +/- 1.35 L/min.

Main effect of training F(1,20)=7.57, p=0.012; group-by-training interaction p=0.02; significant post hoc increase in Caucasian group only.

Mixed

Stroke volume

Stroke volume increased in Caucasian women from 97.77 +/- 11.09 to 109.23 +/- 13.83 mL but changed little in Hispanic women, from 99.73 +/- 11.22 to 100.17 +/- 7.44 mL.

Main effect of training F(1,20)=7.16, p=0.015; group-by-training interaction p=0.022; significant post hoc increase in Caucasian group only.

Mixed

Training adherence and enjoyment

Training-session compliance was 99.5%, and enjoyment did not decline across the intervention.

PACES session 1 versus 9: 88.2 +/- 17.2 vs 90.5 +/- 19.5, p=0.37; group p=0.40; interaction p=0.34.

Mixed

Insights

  • A short, low-volume, three-session-per-week HIIT block with 8-10 minutes of hard work per session can improve VO2max in inactive young women under supervision.
  • Adding one interval per week is a simple progression model for short HIIT blocks.
  • Power-based cycling protocols need adaptation for consumer bodyweight or mixed-modality workouts because peak power output testing is not generally available.
  • Ethnicity-specific programming claims should not be made from this small pilot study.

Limitations

  • Small pilot sample.
  • No non-exercise control group.
  • Women only.
  • Healthy, non-obese, young adult sample.
  • Short intervention duration.
  • Self-reported ethnicity without DNA confirmation.
  • No body composition or autonomic function measurement.
  • Supervised laboratory cycling protocol limits translation to unsupervised app use.

Safety

  • Safety and adherence details were not reported in the paper.