When your muscles contract repeatedly during intense training, they quickly use all available energy. So your body searches for fat. At the same time, your body’s ability to flush metabolic by-products diminishes. You know that burning sensation in your muscles? That’s a build-up of ammonia and other bad stuff. These wastes interfere with your body’s ability to contract muscles forcefully. If you don’t learn to manage the burn properly, your workout is doomed. Interval training helps.
When repeated bouts of high-intensity intervals are separated by short rest periods, each bout begins with an energy deficit and muscles that are already fatigued. “Interval training challenges energy systems in the body. As a result, blood supply to cells increases, the cells use oxygen more efficiently and the enzymes that help create energy also increase. This improves fitness,” says sports doctor Dr Jeramie Hinojosa. What’s more, recovery from interval training forces the body to continue burning fat for energy. This all leads to an increase in the number of kilojoules you burn after a workout.
There are lots of ways to do intervals. Over time you can adjust the ratio of rest to work, the intensity of your working session or the length of the entire workout. The interval programme that my colleagues and I have developed produces truly amazing results and is perfect for people who don’t like endurance training.
As part of an experiment to test the ability of a dietary supplement to flush metabolic waste products from muscle tissue, we put a groupof active varsity students (36 men and 33 women) through six weeks of high-intensity interval training on an exercise bike.
Instead of the usual 30-seconds-on, 30-seconds-off approach, we had the students pedal intensively (at 90 percent of maximum effort) for two minutes, rest completely for a minute and then repeat that sequence four more times. That’s only 10 minutes of training. Even with the warm-up and rest periods, they were looking at a 20-minute time investment. After nine workout sessions over just three weeks, all 69 participants saw huge benefits.
The maximum amount of oxygen they could take in – a measure of cardiovascular fitness – increased by 11 percent. What’s more, they were able to pedal 12 percent longer and do 44 percent more work. After six weeks, the improvements were even more dramatic. There was an 18 percent climb in fitness, 17 percent improvement in time to exhaustion and nearly 100 percent improvement in work done.
You can achieve the same results by using the workout chart with this article. Measuring your effort accurately and training accordingly is key to success.
The best way to measure effort without loads of scientific gadgetry is to measure your heart rate using a monitor so that you can train at a certain percentage of your estimated maximum heart rate (MHR).
Your MHR is 220 minus your age. If you’re 28, then, the magic number is 192 beats per minute (bpm). So the goal for your first session would be to elevate your heart rate to about 173bpm (192 × 0.90, for 90 percent of MHR) for all work intervals. If you look at your heart-rate monitor and you’re not there yet, push those pedals until you are. After two minutes, exercise lightly or rest.
Perhaps you’re wondering whether training at more than 100 percent of your maximum heart rate, as the workout chart suggests, is even safe. The answer is yes. Your body will adjust as soon as you start training intensively. What seemed like 100 percent one week will be a level you can surpass the next.
If you don’t own a heart-rate monitor – or find one hard to use while you’re shifting gears, as intervals require – do it the old-fashioned way. Immediately after each interval, place your index and middle fingers on your neck just to the side of your Adam’s apple or on the thumb side of your wrist. Once you feel a pulse, count the beats for 15 seconds. Multiply by four to determine your heart rate.
Bear in mind that even the lowest training level here (90 percent of maximum effort) is quite intense. By the time you reach 100 or higher, you should be pedaling for your life. You can also trade the exercise bike for any other apparatus that elevates your heart rate such as a treadmill, elliptical trainer or even a skipping rope. As an avid runner, I wish I had known about high-intensity interval training earlier in my career. It would have brought me huge gains for only 15 minutes of cardio, three times a week.