Categories / HIIT & conditioning
Featured in: Exercise for type 2 diabetes, Exercise for busy people, 15 and 20-minute workouts, Getting fit after 40, Best exercise for weight loss, Best exercise for belly fat
HIIT
Short maximal efforts alternated with rest.
How to start
Warm up for 5 minutes. Then do 6 rounds of 30 seconds hard (you can say only a few words) and 90 seconds easy. Cool down for 5 minutes. Start with two sessions a week.
How to progress
Add rounds, then lengthen the hard part to 45 or 60 seconds. Keep at least a day between hard sessions and add easy activity on other days.
What the evidence says
Evidence: moderate
A 2026 pooled analysis of 40 trials (1,460 people) found that sprint interval training improved insulin resistance and LDL cholesterol compared with no exercise, and gave broadly similar results to steady moderate exercise. The authors rated the certainty of the evidence as low to very low. A 2026 review of 25 studies in adults aged 60 and over found HIIT improved fitness (VO2peak), though it did not show that it beats steady exercise, and reporting of side effects was inconsistent.
Take care: Hard intervals strain the heart. See a GP first if you have heart disease, high blood pressure, chest pain or you are over 50 and inactive. Stop if you feel dizzy or have chest pain.
Sources
12-week starter plan
Two sessions a week at first, then three. Pick any activity: brisk uphill walking, cycling, rowing or running. Weeks 4, 8 and 12 repeat the previous load.
Tick each week as you finish it; your ticks are saved on this device only. Repeat a week if it felt hard. Weeks 4, 8 and 12 hold steady so you can settle. This is a general plan, not medical advice.
Add reminders to your calendar
Pick your days and time. You will download a calendar file that adds 12 weeks of reminders to Google, Apple or Outlook calendar.
Calories and weekly minutes
Enter your details for a rough estimate. Based on about 8 METs (Typical effort for this activity (estimated)). Real figures vary by 20% or more between people.
Tips and common mistakes
Tips
- Hard means you can only say a few words.
- Warm up properly.
- Keep easy days easy.
Common mistakes
- Doing hard sessions on back-to-back days.
- Going all out from week one.
- Skipping the warm-up and cool-down.
Kit and cost
Free to low Approximate UK prices.
- Supportive trainers
- A timer or interval app
- Optional: a bike, rower or treadmill
Frequently asked questions
Is HIIT better than steady exercise?
Reviews found similar benefits for many outcomes. HIIT takes less time but is harder.
How often?
Two or three times a week is plenty.
Is it safe for me?
Check with a GP first if you have a heart or blood pressure condition or are inactive.
Good for: Weight loss Heart & fitness Power & speed
Compare with similar options
| HIIT | Tabata | Sprint Interval Training | Norwegian 4x4 | |
|---|---|---|---|---|
| Typical session | 25 min × 3/wk | 4 min × 4/wk | 15 min × 3/wk | 40 min × 2/wk |
| Effort | ●●●●● | ●●●●● | ●●●●● | ●●●●● |
| Cost | Free | Free | Low cost | Low cost |
| Equipment | No equipment | No equipment | Some equipment | Basic kit |
| Impact | Medium impact | Medium impact | Medium impact | Medium impact |
| Fitness needed | Some fitness | Moderate fitness | Moderate fitness | Moderate fitness |
| Evidence | moderate | limited | moderate | limited |