NZ Woman's Weekly
About high-intensity impact training (HIIT)

About high-intensity impact training (HIIT)

Forget spending hours sweating it out at the gym or pounding the pavements to improve your fitness – according to British scientists, all it may take is just three minutes a week. Yes, really. Researchers at the universities of Nottingham, Birmingham and Bath claim that exercising in short, intense bursts can have the same impact on your health as longer stretches of physical activity.

Instead of jogging or walking briskly for half an hour, frantically running up and down steps for half a minute at a time may give you similar results. The key is to do three 30-second bouts of exercise that leave you breathless and take short rest periods in between.

The scientists say so far results from trials into the effects of short bursts of exercise have been ground-breaking and could revolutionise the way we think about physical activity. They have been studying what they call HIIT (high-intensity impact training) for eight years, with the last lot of trials carried out on 300 unfit volunteers last year.

Results consistently show that short bursts of exercise profoundly boost stamina and improve the fitness of lungs, heart and blood vessels. The researchers don’t fully understand why it works and are carrying out further trials, but say it could change the advice given to people about how long they should exercise for.

An added bonus of HIIT is that it can be more effective in helping you to lose weight. Exercising for longer periods can leave you hungry, so you end up eating and undoing the good work you’ve just done burning off calories.

Brief, high-intensity exercise raises metabolism and encourages your body to break down fat and burn calories, but it doesn’t stimulate appetite as much as exercising for longer because it requires less energy expenditure. Other studies back up the findings, including one carried out at the University of New South Wales in Sydney.

Scientists found that sprint training for 60 minutes a week is as effective when it comes to burning body fat as jogging for seven hours a week. They got 50 overweight men to spend 20 minutes on an exercise bike, sprinting for eight seconds then resting for 12 seconds.

They did these 20-minute sessions three times a week for 12 weeks and lost an average of 2kg of abdominal fat, as well as increasing their muscle mass. They also reduced dangerous fat around their liver, kidneys and other internal organs by 17%. This visceral fat is strongly linked with an increased risk of heart disease.

Other studies found that to lose the same amount of visceral fat, it took 14 weeks of doing seven hours of moderate intensity aerobic exercise each week. The Australian scientists believe high-intensity regimes work because rapid bursts of muscle movement appear to flood the blood with hormones called catecholamines, which break down fat stores and burn them as energy. Moderate-intensity exercise, even for longer periods of time, barely raises blood levels of catecholamines at all.

HOW TO DO HIGH-INTENSITY IMPACT TRAINING

1. Warm up for a couple of minutes until you are exercising at a moderate pace and gently stretching your muscles.

2. Exercise as hard as you can (for example sprinting or cycling) for 30 seconds without stopping. This should make you breathless.

3. Rest for up to a minute then do it again. Repeat three times within the space of five minutes.

4. Do this at least twice a week. Make sure you see your doctor before starting a new exercise regime, especially if you are inactive or have a history of heart problems or breathing difficulties.

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