PMID 41003007

Research
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High-Intensity Interval Training (HIIT): Impact of Duration on Body Composition, Cardiometabolic Health, and Aerobic Capacity in Adolescent Women

Stankovic M, Čaprić I, Pezelj L, Biševac E, Mekić R, Zećirović A, Salihagić Z, Ajdinović A, Jelaska I

Question

How do 6-week and 8-week HIIT programs affect body composition, lipid profile, blood pressure, glucose, and aerobic capacity in adolescent women aged 17-19?

Summary

This randomized experimental study compared 6-week and 8-week running HIIT programs with a control group in healthy, normal-BMI adolescent women. Both HIIT durations improved body weight, BMI, body fat percentage, lipid markers except HDL, blood pressure, and estimated VO2max. The 8-week program had stronger effects on triglycerides and total cholesterol, while glucose and HDL did not significantly change.

Methodology

  • Healthy adolescent women with normal BMI.
  • 122 participants.
  • Running.
  • Work intervals: 30 seconds at 90-95% HRmax.
  • Recovery: 30 seconds active recovery at 50-55% HRmax.
  • Intensity: 90-95% HRmax work, 50-55% HRmax recovery; actual mean work HR approximately 185-186 bpm and peak 192-193 bpm.
  • 15-minute warm-up plus interval block plus 15-minute cooldown.
  • 2 sessions/week.
  • 6 weeks in HIIT 1 or 8 weeks in HIIT 2.
  • Randomized experimental pre/post study with two HIIT-duration groups and a control group.
  • Body composition, Lipid profile and glucose, Blood pressure, and Aerobic capacity were tracked.

Outcomes

Body composition

Both HIIT durations reduced body mass, BMI, and body fat percentage compared with control.

All p<0.001; BMI reduction of about 1.1 kg/m2 exceeded the authors' Delphi-derived clinical threshold.

Improved

Lipids

Total cholesterol, triglycerides, and LDL improved in both HIIT groups, with stronger triglyceride and total cholesterol effects in the 8-week group; HDL did not change significantly.

TC, TG, LDL all p<0.001; HDL p=0.825; HIIT 2 showed more pronounced TG and TC reduction than HIIT 1.

Improved

Blood pressure

Systolic and diastolic blood pressure improved after both HIIT programs.

SBP and DBP p<0.001; reductions exceeded Delphi-derived clinical thresholds.

Improved

Glucose

Fasting glycemia did not significantly change.

p=0.078.

No clear change

Aerobic capacity

VO2max increased after both 6 and 8 weeks, with no significant difference between HIIT durations.

p<0.001; authors discuss approximately 18% improvement during the 8-week intervention.

Improved

Insights

  • A 30/30 running HIIT program can be progressed by adding one interval pair every two weeks.
  • Six weeks may be enough for fitness and body-composition changes in healthy adolescent women, while lipid outcomes may benefit from 8 weeks.
  • This protocol is most applicable to screened healthy adolescents with HR monitoring.

Limitations

  • VO2max was estimated by shuttle run rather than measured directly.
  • No long-term follow-up.
  • Dietary habits, sleep, menstrual cycle phase, physical activity, and socioeconomic level were not controlled.
  • Population was healthy, normal-BMI adolescent women, limiting generalizability.
  • Adverse-event reporting was not clear.

Safety

  • Adverse events were not explicitly reported in the paper.
  • Participants with contraindications, acute injuries/illness, heart disease, or metabolism-altering medication use were excluded.