PMID 27774458

Research
All papers

Short-Term High-Intensity Interval Training on Body Composition and Blood Glucose in Overweight and Obese Young Women

Kong Z, Sun S, Liu M, Shi Q

Question

How does 5 weeks of brief cycling HIIT compare with moderate continuous cycling for aerobic fitness, body composition, fasting glucose, hormones, energy expenditure, and perceived exertion in inactive overweight/obese young women?

Summary

In inactive overweight or obese young women, 5 weeks of 20-minute cycling HIIT using repeated 8-second hard efforts and 12-second passive rests improved VO2peak and peak power about as much as 40-minute moderate continuous cycling, with roughly half the time and energy expenditure. Neither program changed fat mass or relevant fasting hormones, and glucose only trended downward. HIIT was perceived as easier than MICT in this sample.

Methodology

  • Inactive overweight or obese young women recruited through local media in Macau.
  • 22 participants.
  • Cycle ergometer.
  • Work intervals: 8 seconds cycling as hard as possible.
  • Recovery: 12 seconds passive recovery.
  • Intensity: All subjects worked as hard as they could; measured first session around 89% VO2peak during exercise phases.
  • 20 minutes.
  • 4 sessions/week.
  • 5 weeks; 20 sessions.
  • Randomized controlled exercise training trial
  • VO2peak and peak power output, Body composition, Fasting glucose and hormones, and Training HR, RPE, and energy expenditure were tracked.

Outcomes

VO2peak and PPO

Both HIIT and MICT significantly improved VO2peak and peak power, with no significant between-group difference.

VO2peak p=0.006, eta2=0.38; PPO p<0.001, eta2=0.61; HIIT +7.9% VO2peak and +13.8% PPO; MICT +11.7% and +21.9%.

Improved

Perceived exertion and energy expenditure

HIIT took less time, used less energy, and was perceived as easier than MICT despite similar training HR.

HR 164 +/- 8 vs 160 +/- 12 bpm, p=0.435; RPE 13 +/- 1 vs 15 +/- 1, p=0.042; total energy 3167 +/- 549 vs 6011 +/- 505 kcal, p<0.001.

Improved

Body composition

Neither group significantly changed weight, BMI, total fat mass, total body fatness, or trunk/abdominal fat/lean measures; MICT lost lean mass but authors suggested possible DXA measurement error.

MICT total lean mass -1.7 kg, p=0.011; leg lean mass -0.6 kg, p=0.018; HIIT lean mass unchanged.

No clear change

Fasting glucose and hormones

Fasting glucose showed a trend toward decrease with no group difference; systemic hormones did not change.

Fasting glucose p=0.062, eta2=0.213; no within- or between-group hormone differences.

Mixed

Insights

  • Very short 8-second/12-second cycling intervals can improve aerobic fitness quickly in inactive young women with overweight/obesity.
  • This short HIIT dose should not be sold as a body-fat-loss protocol over 5 weeks.
  • Lower RPE than MICT suggests short alternating intervals may feel more approachable for some inactive users.

Limitations

  • Small sample limits body-composition conclusions.
  • No nonexercise control group.
  • Seasonal timing may have affected weight/body composition.
  • Future studies should better manage demographics, menstrual cycle, physical activity, and nutrition.

Safety

  • No adverse events were described.
  • Participants completed PAR-Q, medical history, and physician clearance for vigorous exercise.
  • One HIIT and three MICT participants quit before completing training for personal reasons.