This article by Jeannnine Stein in the LA Times provides a nice summary of a study conducted in Wales on a small group of adolescents (i.e., teeney boppers) to determine the comparative effectiveness of aerobic exercise versus high intensity exercise in reducing cardiovascular disease (CVD) risk factors.
This TOJ found the results shown in this excerpt from the actual study, which was headed up by Duncan Buchan, to be very cool and encouraging. No doubt the body of an adolescent will adapt more quickly over a short period of time to the stress of exercise, but likely the findings would be the same with more mature adults. To help you decipher it, MOD stands for moderate aerobic exercise and HIT stands for High Intensity Training:
Results: Total exercise time commitment over the intervention was 420 min (MOD) and 63 min (HIT). Training volume was 85% lower for the HIT group. Total estimated energy expenditure was 907.2 kcal (HIT) and 4410 kcal (MOD). Significant improvements (P 0.05) were found in systolic blood pressure, aerobic fitness, and body mass index (BMI) postintervention (HIT). In the MOD group, significant (P 0.05) improvements were noted in aerobic fitness, percentage body fat (%BF), BMI, fibrinogen (Fg), plasminogen activator inhibitor-1, and insulin concentrations.
What's noteworthy is BOTH aerobic training (in this case 20 min. runs at a moderate pace three times a week) and intense intervals (all out sprints for 40 meters alternated with short rest periods over just a few minutes three times a week) had very positive, if slightly different, impacts on improving CVD risk factors.
Obviously how you train depends on what you are trying to accomplish. If your goal is to burn calories, you are better off running distance. If your goal is to get significant training benefits in a short period of time, choose high intensity. It's pretty amazing how much could be accomplished with HIT in only 15% of the time required by aerobic exercise. Many of us don't have a lot of spare time. As this study proves, it doesn't take much.
In the past year, the TOJ has written a lot about the relative benefits of the two. In the exercise world, there are camps of people who are almost religious zealots about the exclusive advantages of one over the other. The truth isn't either/or, but both. Some days there's no substitute for a short, killer, high intensity workout. Other days there's no substitute for a leisurely run. Just follow your bliss. Either way you'll end up fitter.