In the past couple of years, there has been some buzz about the possibility that high-intensity, short duration exercise can be as beneficial to your health as spending more time in exercise at moderate intensity. I've always been a little skeptical about that, since my experience has proven that the longer I exercise, the healthier I feel.
Recently, a group of Danish researchers did a study to find out just which health markers high-intensity training improved. The study, printed in the October 2010 issue of Medicine and Science in Sports and Exercise had subjects split into four groups. One group did high intensity sprint workouts in which they warmed up for five minutes, then did five two-minute intervals of near maximal running. One group did an hour of running at 80 percent of their max heart rates three times a week. (That is still pretty aggressive; I usually train at about 65-75 percent of my max if I'm doing an hour or more). One group did no aerobic exercise at all, instead they strength trained for hour twice a week. And the last group, the control group, remained sedentary.
The results were interesting. VO2MAX for the high intensity group shot up significantly. The moderate intensity longer duration group increased their VO2MAX as well, but not as much.
As far as health markers go, all three of the exercising groups saw drops in their systolic blood pressure (although the duration runners saw the biggest drop and was the only group to see a drop in diastolic blood pressure). The duration runners were also the only group to see a significant reduction in their cholesterol ratio (the ratio of total cholesterol to HDL cholesterol. The lower this number, the better). Glucose tolerance was improved in both running groups, but not the strength training group. On the other hand, strength trainers increased their bone density, but the running groups didn't.
But here's the clincher. Only the moderate intensity longer duration group reduced its body fat percentage. Interval trainers did not. And strength trainers (at least in this study) actually increased their body fat percentage (!)
The bottom line is that if you are an athlete looking to improve VO2MAX for performance, choose short duration, high intensity exercise. But if you are looking to improve your health, nothing beats putting the time into a good long run. Or swim. Or bike ride. Or evening of dancing.