Your action plan

What?
Three workouts that force your body to burn fat for energy long after you've stopped exercising.

Why?
The built-in "fat-burning zone" on most cardio machines means a long, slow slog to nowhere. Yes, you'll burn fat, but as a study by the American College of Sports Medicine shows, if you push your effort level beyond this zone and combine sprints with rests, you'll burn more kilojoules overall and shift just as much fat in less time.

How?
Strap on your heart-rate monitor and pick a new plan each day depending on your goals and schedule. It's as easy as choosing a shirt in the morning.

Who?
Anyone who has a heart-rate monitor who wants to get rid of those unwanted kilos.

When?
Do a new workout three times a week or focus on a particular goal for an entire week, such as boosting your match fitness. Match the program to suit your needs, but make sure you leave a day's rest between each bout to fully recover.

The myth
220 minus your age is your maximum heart rate.

The truth
A 2007 study in the journal Medicine and Science in Sports and Exercise found that 207 minus (your age x 0.7) is the most accurate measure of your maximum heart rate. So, if you're 30, your max heart rate is 207 - (30 x 0.7) = 186 beats per minute (bpm). Next, calculate 35, 50, 65 and 90 per cent of that figure, as you'll need to know these to follow the routines.

Best for a tight schedule

1. Run at an easy pace - normally about 35 per cent of your maximum heart rate - for three minutes.
2. Sprint so your heart rate reaches 90 per cent of your maximum. Do this for six seconds.
3. Slowly jog or walk until your heart rate drops to 60-65 per cent of your maximum and keep it there for 12 seconds.
4. Repeat this for a period of 16 minutes then walk for two minutes until your heart rate drops to 35 per cent of your maximum.

WHY?
A study in the European Journal of Applied Physiology asked men to do long or short intervals for 16 minutes. The first group sprinted at approximately 90 per cent of their maximum for six seconds and had nine seconds' rest at 60-65 per cent of their maximum. The second group did intervals four times as long. The short intervals were found to burn almost three times more fat than the longer intervals. "These intervals are generally impractical on gym machines, as it takes too long to alternate speeds, so try a 15-second sprint followed by 30 seconds of recovery instead," says Christian Finn, author of website thefactsaboutfitness.com.

Best for weight loss

1. Cycle at 30 per cent of your maximum heart rate for five minutes.
2. Stand up in the saddle and sprint for eight seconds at 90 per cent.
3. Sit down on your seat and cycle gently until your heart rate drops to 65 per cent of your maximum and keep it there for 12 seconds.
4. Repeat this for 20 minutes.

WHY?
Research at the University of New South Wales found that 20 minutes of sprinting on a bike for eight seconds followed by 12 seconds of recovery burnt five times more fat than riding at one speed for 40 minutes. "Other types of interval training using longer work and rest periods were not found to be as effective," says the study's co-author, Dr Steve Boutcher. This regimen can be applied to any cardio exercise, so there's no excuse for any cyclophobes out there.

Best for getting fitter

1. Warm up by running at 50 per cent of your maximum heart rate for five minutes.
2. Row for two minutes on resistance level eight at 90 per cent of your maximum heart rate.
3. Recover by rowing for three minutes on resistance level 10 at 30 per cent of your maximum.
4. Repeat this for 30 minutes.

WHY?
A study in the journal Medicine and Science in Sports and Exercise found that when people alternated between two minutes of exercise at 90 per cent of their maximum heart rate then recovered for three minutes at 30 per cent of their maximum heart rate, they increased their cardiovascular fitness by 13 per cent over those who exercised at the same pace. Both groups trained until 1250kJ were burnt, but the interval group's metabolism was 5.4 per cent higher 24 hours after exercise. Proof that fitness equals belly flatness.