You can trim 3.5cm from your tummy in six weeks and it doesn’t require hours at the gym – you just need to pick up the pace. This exercise doctor explains how.
Interval sprinting is typically a short burst of exercise at near all-out intensity, followed by low-intensity exercise, which is repeated again and again.
It can be applied to many types of exercise, including cycling, running, rowing, boxing and skipping. We use an eight-second sprint followed by 12 seconds of low-intensity exercise for a period of 20 minutes.
In studies of both men and women doing one hour of interval sprinting a week, after six weeks participants had lost 3.5cm from their waist and maintained that loss after 12 weeks. Doing aerobic exercise, such as jogging or swimming, can also reduce the amount of belly fat but it takes at least five hours a week at a moderately hard intensity.
Even then the results aren’t as good as interval sprinting. The average loss of waistline after 70 hours of aerobic exercise is just 2cm. And resistance exercise by itself doesn’t seem to reduce belly fat in most people.
Science isn’t entirely sure why interval sprinting works so well on belly fat, but it’s thought that the fast muscle movements and elevated heart rate increases the amount and improves the performance of particular fat-burning hormones in the body (such as catecholamines).
As a result of this, fat-burning is significantly increased.
Science has shown that interval sprinting also improves aerobic fitness and muscle mass while decreasing insulin resistance, so the benefits extend way beyond your waistline.
The interval sprinting weight-loss program
How often: Three 20-minute sessions a week.
Warm up: Your choice of aerobic exercise at a gentle pace for four minutes.
Interval sprints: Do an eight-second sprint followed by 12 seconds of low-intensity exercise for 20 minutes.
Cool down: Your choice of aerobic exercise at a gentle pace for four minutes, then stretch.
When to work out: Interval sprinting is best done early in the morning, before breakfast, as exercising after an overnight fast will burn more belly fat. Otherwise exercise at least two hours after your last meal.
What to eat before and after: Have water or green tea before exercise and water after. Avoid eating for at least two hours before exercise and at least 30 minutes after. Eating sugars or protein elevates blood insulin levels, which impairs fat burning.
6 ways to sprint off your belly
1. Sprint cycling: This is the most researched method and has proven results. It’s also recommended for most people as it’s non weight-bearing. You need a stationary bike that will withstand high pedal rates and allows you to set the pedal resistance. Your level of resistance and revolutions per minute will vary according to age and fitness, but a middle-aged woman with no health issues could start on a 0.5kg resistance, sprint at 100 revolutions per minute, and then do 12 seconds at 60 revolutions per minute.
2. Sprint rowing: This method is also non weight-bearing and involves more muscle than cycling. You’ll need a rowing machine that allows you to set the resistance. Sprint row for eight seconds, then do an easy row for 12 seconds.
3. Spring running: Use a running track or mark out an area on a flat, grassy surface. This is the hardest method and may put too much stress on joints for some. Sprint for eight seconds, then walk for 12 seconds.
4. Sprint boxing: Punch continuously on a punching bag for eight seconds, then shadow-box for 12 seconds.
5. Sprint skipping: Skip for eight seconds then do a light jog on the spot for 12 seconds.
6. Sprint circuit: This is a good option for people who like variety. Choose a mix of interval sprints such as five minutes of boxing, five minutes of skipping, five minutes of rowing and five minutes of cycling.
Tips for starting out
Seek a doctor’s OK first: Get medically screened by your GP or an accredited exercise physiologist. This is especially important if you’re older, have any risk factors, diseases or are on medication. Interval sprinting significantly increases your heart rate, which may not be safe for some people.
Know your heart rate: This is one of the most important ways of measuring your performance during interval sprinting – it will tell you if you’re going too hard, too fast or not hard enough!
Here are some typical heart rate averages for healthy people during interval sprinting:
For people under 30: The ideal heart rate is about 150 beats per minute after five minutes, increasing to 160 beats per minute after 20 minutes and dropping to 100 after the cool-down phase.
For middle-aged adults: Ideally your heart rate will be about 140 beats per minute after five minutes, increasing to 150 beats per minute after 20 minutes and dropping to 90 beats per minute after the cool-down phase.
For a 60-year-old: Optimal heart rate is about 120 beats per minute after five minutes, increasing to 130 after 20 minutes and dropping to 80 after the cool-down phase.
How to measure your heart rate: Locate your radial pulse on your wrist and use a personal heart rate monitor or one attached to your exercise equipment. It’s also important that your heart rate drops at the end of the four-minute cool down period (to between 80 and 100 beats, depending on how high it reached during the workout).
Start slow: If you’re unfit, try going for 10 minutes and see how you feel at the end of the session and when you wake up the next day. If everything is fine, increase the exercise time to 15 minutes during week two. By week three, most people should be able to complete the full 20 minutes and may also need to increase their pedal rate. Most people will start breathing heavily and sweating after five minutes of sprinting, so keep a towel nearby. Your legs will feel tired at the end of 20 minutes.
Count the intervals: You can download apps for iPhones and Android devices that allow you to create your own interval sprinting program. Music specifically developed for the 20 x 3 interval program called LifeSprints is available on iTunes.
This is an edited extract from 20×3: Eliminate Your Belly Fat In An Hour A Week, By Dr Steve Boucher ($19.99, Black Inc)