Fit or Fiction: Intense Workouts For Faster Weight-Loss Results

I read recently that doing really intense workouts can drastically cut down the amount of time I need to exercise. Is that true? -- Janet Borden, N.J.

In a recent, highly publicized interview, an exercise scientist from Norwegian University of Science and Technology claimed that high intensity exercise is twice as effective as normal exercise. When compared to people on a regular exercise routine, like hopping on a treadmill and walking at a moderate pace for 45 minutes, he said, those doing interval training can double their endurance, improve their speed by at least 5 percent and up their oxygen use and strength by more than 10 percent.

There are a stack of studies to support this point of view. In 2009, University of Copenhagen researchers found that runners who reduced the amount of running they did by 25 percent and substituted three to four runs a week with sprint workouts improved their 10K race times by an average of a minute and in one case, by over two minutes.

Another study done at McMaster University in Canada found that a few short bursts of high intensity activity interspersed with rest periods (the definition of interval training) can produce the same results as slow and steady endurance training. And according to the Norwegian investigators, even heart patients and the elderly show better oxygen use and fitness after doing interval training.

If you're always short on time for exercising, you should definitely consider substituting one to three longer workouts a week with shorter, high intensity sprint-type workouts. Or, if you're looking to push past a fitness or weight loss plateau, I have long been a proponent of adding in some high intensity work into your routine. Some studies show interval training is more effective for fat and weight loss, despite the fact that the primary fuel burned during this type of exercise is carbohydrate. This could be because metabolism stays revved up for several hours after an especially heart pounding workout session.

However, if you're just starting out, very overweight or have some type of medical condition (such as injury-prone joints), I recommend easing into this type of training -- and certainly get clearance from a physician before you dig out your stop watch and head for the track.

If you're new to interval training, try a 1:3 sprint/rest pattern. On the treadmill, for instance, warm up for at least 10 minutes. Then alternate one minute of running at a speedy pace with a jog or walk for three minutes at an easy pace. Repeat the cycle three to five times, gradually increasing the number of interval cycles as you become more fit. Don't forget a five minute cool down post-workout. Another way to make intervals tougher is to take less rest in between. For instance, as you get in better shape, you might sprint for three minutes and jog for two minutes. You can also lengthen the sprint periods -- but if you take them much beyond five minutes, you probably aren't challenging yourself enough to get the results you're looking for.

High intensity means pushing yourself to a point where you can barely speak, your heart is thumping in your chest and you are soaked, if not dripping, with sweat. On a scale of one to 10, with 10 being the hardest you can work, you want to aim for an effort between seven and nine. On the heart rate monitor, you should be at 70-90 percent of your max heart rate. (Check out these articles for the correct exercise intensity or max heart rate.)

Those who don't tolerate high impact very well can do their interval training on a bike, in the pool, on an elliptical trainer or try any other type of workout they find to be the most joint-friendly. Start with one interval workout a week to give your body time to reboot between workouts. When your body has adjusted to that, gradually increase up to four high intensity sessions a week.

I myself do at least two interval type workouts a week; I either sprint, do a killer class, some circuit training, jump rope or spin hard on the elliptical trainer. I sometimes use a heart rate monitor and sometimes I go by how I feel.

What about you? I'd love to know if you've had good -- or bad -- results from sprinkling intervals into your routine, especially if it has helped you lose weight. Post it here or tweet me @lizzyfit.