The words "interval training" can strike fear in the hearts of even the most athletic men and women. Alternating periods of high-intensity work with recovery may sound simple enough, but those intense bouts can leave the exerciser gasping for air.
It's that intensity that ultimately reaps great benefits, including strengthening the heart and improving the cardiovascular system, which is why personal trainers tend to favor interval training. Higher exercise levels can be achieved by upping the speed or the resistance -- think walking faster on a treadmill, increasing the incline, or both.
Intervals can be done on cardio equipment such as stationary bikes and elliptical trainers, and runners can toggle between slower speeds and sprints. Strength-training circuit workouts can even incorporate them by adding full-body exercises.
Here, three trainers explain how to integrate interval workouts into an exercise plan.
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The basics of interval training are tough to figure out without doing some math first to figure out one's maximum heart rate.
A general formula for calculating that number is 220 minus age. To work in a lower aerobic zone, in which the body burns primarily fat for fuel, calculate 65% of the maximum heart rate. To work in a higher anaerobic zone, calculate 85% of the maximum heart rate. The anaerobic zone, in which the body burns primarily carbohydrates for fuel, is the high-intensity portion of the interval (some trainers may put it at about 80%). For those who like precise numbers, some gyms and training facilities offer more technically advanced testing, but that can be costly. Heart rates can be taken manually at the wrist, and some cardio machines have built-in monitors (although accuracy varies). Heart-rate monitors provide the best readings.
Tony Ambler-Wright
Scottsdale, Ariz.-based master instructor for the National Academy of Sports Medicine:
We take our clients in and out of three zones: Zone 1 is 65% to 75% of your maximum heart rate, and Zone 2 is 80% to 85% of your maximum heart rate. Zone 3 is 85% to 90% of your maximum heart rate, and you usually don't want that to comprise more than 10% of your total training volume for the week because it's so intense. But ultimately the goal is to get everyone to that point where they could exercise at that level of intensity.
