High-intensity interval training is the new buzz phrase in exercise science, and it yields greater fat oxidation during workouts, potentially resulting in greater long-term weight loss. You can adapt this type of training to your cardio workout regardless of the type of training you currently practice.
Expert Insight
A study published in the Dec. 14, 2006, issue of the "Journal of Applied Physiology" indicated increased fat oxidation during exercise among study participants performing high-intensity interval training. The study analyzed eight healthy weight women who engaged in 10 four-minute bursts on a stationary bicycle followed by two-minute rest periods. Researchers tracked the women's VO2 peak, resting muscle glycogen and fatty acid transport during and after the exercise. They found that after seven 60-minute workouts of high-intensity interval training over a two-week period, study participants' whole body fat oxidation increased by 36 percent.
How it Works
Typically during exercise, the body reaches to a combination of stored fat and carbohydrates for energy, depending on how hard you're working. When you're exercising at a level more than 75 percent of your maximum heart rate, the amount of oxygen available for fat metabolism decreases, resulting in all energy coming from stored carbohydrates. In the study, increased fat oxidation during exercise might have resulted from improved cardiovascular capacity---maximal oxygen consumption increased by 13 percent, and heart rates were lower during the last half-hour of training---yielding greater oxygen available for fat-burning during exercise.
Training for Weight Loss
Women in the study exercised for 60 minutes each day between three and four days per week for a total of 180 to 240 minutes each week. However, for weight loss it's not enough to simply walk for three or four hours a week because this does not increase cardiovascular fitness and fat oxidation. Furthermore, the intensity of the exercise directly affects the total amount of energy burned whether from stored fat or carbohydrates, meaning a moderate workout yields moderate levels of energy used. Another study published in the October 2005 issue of the "Journal of Applied Physiology" found that the equivalent of 20 miles per week of jogging resulted in weight loss, particularly around the midsection, whereas 12 miles per week of walking had no effect on stored belly fat.
Incorporating It Into Your Program
Whether you run, cycle, swim or row, you can incorporate interval training into your exercise program. Simply follow the basic time outline of four-minute bursts followed by two-minute recovery periods for 60 minutes three or four days each week.
Caution
As with any exercise program, you should consult your physician before beginning. This particular program could place additional strain on your cardiovascular system, and you should monitor your heart rate closely to ensure it does not rise above your maximum heart rate, which is 220 minus your age in years. For example, the maximum heart rate for a 50-year-old would be 220 - 50 = 170.
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