PMID 34987589

Research
All papers

Alternating high-intensity interval training and continuous training is efficacious in improving cardiometabolic health in obese middle-aged men

Poon ET, Siu PM, Wongpipit W, Gibala M, Wong SH

Question

Do HIIT alone, MICT alone, or alternating HIIT-MICT produce different cardiometabolic, body-composition, fitness, enjoyment, self-efficacy, and adherence responses in inactive obese middle-aged men?

Summary

This randomized trial compared HIIT, MICT, alternating HIIT/MICT, and no exercise for 16 weeks in inactive obese middle-aged Asian men. All exercise groups improved VO2max by about 15% and reduced weight, BMI, body fat percentage, and waist circumference compared with control. HIIT, MICT, and alternating HIIT/MICT had similar enjoyment, self-efficacy, and adherence above 80%, with one minor knee-pain incident in the HIIT group that resolved after brief rest.

Methodology

  • Inactive obese Asian middle-aged men.
  • 42 participants.
  • Running, jogging, or brisk walking on treadmill or outdoors.
  • Work intervals: 1 minute.
  • Recovery: 1 minute walking at 50% HRmax.
  • Intensity: 80-90% HRmax during work bouts.
  • About 29 minutes at full protocol including 3-minute warm-up and cool-down.
  • 3 days/week.
  • 16 weeks.
  • Four-arm randomized controlled trial with three exercise arms and a non-exercise control group.
  • VO2max, Weight, BMI, fat percentage, waist circumference, Fasting glucose, insulin, HOMA-IR, lipids, and Blood pressure were tracked.

Outcomes

VO2max

All exercise groups improved VO2max by about 15% compared with baseline and control.

HIIT 34.3 to 39.1; MICT 34.9 to 39.4; HIIT-MICT 34.4 to 40.3 mL/kg/min; ANCOVA p=0.009.

Improved

Body composition

All exercise groups reduced weight, BMI, body fat percentage, and waist circumference compared with control.

Between-group effects for weight/BMI/fat/waist p<0.05, partial eta squared 0.06-0.09.

Improved

Blood markers

No significant post-intervention group differences for blood markers; HIIT-MICT improved cholesterol/LDL from baseline and HIIT improved fasting insulin/HOMA-IR from baseline.

ANCOVA for all blood markers p>0.05; within-group total cholesterol and LDL decreased after HIIT-MICT; fasting insulin and HOMA-IR improved after HIIT.

Mixed

Adherence, enjoyment, safety

Adherence exceeded 80% and enjoyment/self-efficacy did not differ; one minor knee pain episode occurred in HIIT.

Enjoyment p=0.789, self-efficacy p=0.345, adherence p=0.576.

Mixed

Insights

  • Alternating HIIT and MICT can be presented as an evidence-backed option for users who want variety without sacrificing likely fitness/body-composition benefits.
  • For inactive users, ramping from half volume to full volume over four weeks is a practical progression pattern.
  • When calorie expenditure is matched, HIIT may save time but should not be marketed as clearly superior for fat loss.

Limitations

  • Small sample size.
  • Male-only, middle-aged Asian sample.
  • No direct insulin sensitivity measure such as clamp or OGTT.
  • Mostly free-living training may create uncontrolled variation.

Safety

  • One minor knee-pain incident occurred in the HIIT group and resolved after a few days of rest.
  • No other training-related adverse events were reported.
  • Severe hypertension and unstable cardiovascular disease were excluded.