A co-worker of mine called my attention to a recent study conducted by McMaster University. The entire piece is worth reading, but it can be summed up rather nicely with this excerpt:
People can exercise using brief, high-intensity forms of exercise and reap the same benefits to cardiovascular health that can be derived from traditional, long-duration and moderately intense exercise.
This study underscores the whole concept of evolutionary fitness and power law training. More specifically, it provides empirical evidence that short burst, high intensity forms of physical activity are inherently “cardio-protective” – possibly much more so than endurance training.
Does this mean that one should give up doing endurance sports such as marathons and triathlons? Not at all. In fact, it would be quite hypocritical of me to suggest this to anyone. However, be aware that your body is better designed for certain types of exercises and activities – and that heavy “cardio” exercising beyond an optimal range might actually be counterproductive – if not damaging altogether.