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What is HIIT?

High-intensity interval training in plain words: what it is, what it does and how to try it

What makes it HIIT

Any exercise can become HIIT: running, cycling, rowing, bodyweight moves or kettlebells. What matters is the pattern: an effort hard enough that you couldn’t keep it up for long, then enough rest to do it again. Sprint interval training goes further, with short all-out sprints and long rests 3.

Popular HIIT formats.
FormatWorkRestRounds
Tabata20 s10 s8
40/2040 s20 s8 to 12
30/3030 s30 s10 to 20
4×44 min3 min4
Sprint intervals20 to 30 s, all-out2 to 4 min3 to 6

What it does

  • Fitness: HIIT improves VO2max, a key measure of fitness, and on average more than steady cardio 4.
  • Health: in people with heart and metabolic conditions, it improved fitness about twice as much as moderate exercise 1.
  • Fat loss: about as much as steady cardio, in less time 5,6.
  • Time: in one trial, three 10-minute sessions a week matched three 50-minute ones 7.

Read the full story in HIIT benefits.

How to start

  1. Warm up for 5 to 10 minutes 8.
  2. Start with more rest than work, such as 20 seconds hard and 40 easy, for 8 rounds.
  3. Do it 2 or 3 times a week, with easier days between.
  4. Add rounds or shorten the rest as it gets easier.
Free toolTry a HIIT timer nowRun 40/20 or 30/30 in your browser, free.

Sources

  1. Weston KS, Wisløff U, Coombes JS. High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis. Br J Sports Med. 2014;48(16):1227-1234. doi.org/10.1136/bjsports-2013-092576
  2. Helgerud J, Høydal K, Wang E, et al. Aerobic High-Intensity Intervals Improve VO2max More Than Moderate Training. Med Sci Sports Exerc. 2007;39(4):665-671. doi.org/10.1249/mss.0b013e3180304570
  3. Gibala MJ, Little JP, van Essen M, et al. Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. J Physiol. 2006;575(3):901-911. doi.org/10.1113/jphysiol.2006.112094
  4. Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Med. 2015;45(10):1469-1481. doi.org/10.1007/s40279-015-0365-0
  5. Wewege M, van den Berg R, Ward RE, Keech A. The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: a systematic review and meta-analysis. Obes Rev. 2017;18(6):635-646. doi.org/10.1111/obr.12532
  6. Viana RB, Naves JPA, Coswig VS, et al. Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT). Br J Sports Med. 2019;53(10):655-664. doi.org/10.1136/bjsports-2018-099928
  7. Gillen JB, Martin BJ, MacInnis MJ, et al. Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. PLoS One. 2016;11(4):e0154075. doi.org/10.1371/journal.pone.0154075
  8. Garber CE, Blissmer B, Deschenes MR, et al. Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults. Med Sci Sports Exerc. 2011;43(7):1334-1359. doi.org/10.1249/MSS.0b013e318213fefb

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Cero’s simple timer on iPhone 18 Pro, with the green wave about half full during a high-intensity interval

Cero is a timer, not a medical device. If you’re new to hard exercise, are pregnant or have a health condition, check with your doctor first, and stop if you feel unwell.