HIIT
High-intensity interval training (HIIT) alternates short bursts of all-out effort (sprinting, fast cycling) with periods of rest or easy movement. Compared with long, steady cardio, it takes less time and is often better for fat loss. It grew out of "fartlek" ("speed play") training used by track coaches decades ago.
What the research says
Studies cited by the original article include:
- Laval University (1994): people on a 15-week HIIT programme lost more body fat than people on a 20-week steady-state programme, even though the steady-state group burned about 15,000 more calories in total. The HIIT group's muscles also showed more markers of fat burning.
- East Tennessee State (2001): after 8 weeks, the HIIT group dropped about 2% body fat; the steady-state group dropped none.
- An Australian study: women doing 20 minutes of 8-second sprints and 12-second rests lost far more fat than women doing 40 minutes of steady cardio.
- Baylor (1996) and Florida State (2007): HIIT raised calorie burn for the 24 hours after exercise more than steady cardio did.
- Norwegian University of Science and Technology: in people with metabolic syndrome, HIIT cut a fat-producing enzyme far more than moderate exercise.
- Six weeks of HIIT increased the proteins that carry fat into muscle cells to be burned by up to 50%.
Later research suggests the "afterburn" effect is real but modest, so diet still matters most (see Should Your Workout Kick Your Ass?).
Good for muscle too
Long, slow cardio trains muscle fibres for endurance, which tends to make them smaller. Short, intense work is closer to lifting weights. Studies suggest HIIT helps preserve muscle, and one found cyclists sprinting against heavy resistance had larger testosterone increases. It's also quicker and less boring, and you can do it anywhere: sprints, bike, rower, skipping rope, kettlebells or bodyweight moves.
An 8-week beginner-to-advanced plan
Use any exercise you like. Move up a phase when ready, or stay longer if needed.
| Phase | Weeks | Work | Rest | Rounds | Total |
|---|---|---|---|---|---|
| 1 (1:4) | 1–2 | 15 s | 60 s | 11, plus a final 15 s | ~14 min |
| 2 (1:2) | 3–4 | 30 s | 60 s | 11, plus a final 30 s | ~17 min |
| 3 (1:1) | 5–6 | 30 s | 30 s | 12, plus a final 30 s | ~18.5 min |
| 4 (2:1) | 7–8 | 30 s | 15 s | 26, plus a final 30 s | ~20 min |
Warm up first. Keep "work" intervals truly hard, and "rest" easy (walking or stopping). Two or three sessions a week is plenty alongside weight training (see Cardio and Muscle Growth).
See also
- Cardio and Muscle Growth
- Should Your Workout Kick Your Ass?
- The ONLY 4 Exercises You Need to Grow Stronger
Summary of "The Ultimate 8-Week HIIT-For-Fat-Burning Program" (Bodybuilding.com).