Aerobics gets a bad rap in a lot circles. It is blamed for many injuries that come from repetitive exercise. It is blamed for some suspiciously high rates of cancer and heart attacks among those that perform a large amount of aerobics. People that take aerobics to the extreme, such as marathoners and triathletes, often suffer serious health problems after their competitive careers.
On the other hand, there are a gazillion studies showing the benefits of aerobic exercise. Moderate aerobic exercise can help almost any health condiiton. More vigorous aerobics also shows benefits for some health problems. So which is it, is aerobics healthy or not?
It is easy to see that hunter-gatherers must have performed a large amount of aerobic activity. They covered lots of ground on a hunt, and would often have to chase after wounded prey. Yet their form of "aerobics" was much different than modern versions.
First, it was done outdoors and on grass or dirt. Trail running is much different than street running because 1) the trail is softer and hence easier on the body, and 2) trail running is not a constant, mechanical-type pace; it's more stop-and-start as you navigate around obstacles.
I'm wondering if it's not a high volume of aerobics that is potentially harmful, but instead only the steady-pace version of aerobics. Stop-and-go locomotion is the standard form of locomotion for most animals. It would be curious if humans weren't endowned with this same feature.
Is a high volume of intermittent aerobic activity harmful? It's doubtful, and most likely the opposite is true. This recent study shows that men performing an hour of aerobic activity six days a week showed a lower risk for colon cancer. It does not say specifically that the activity was intermittent, but it is implied from some of the authors' comments (I'm working on getting the full paper).
Personally, I've been doing a good bit of intermittent running these past few weeks, and I can really tell a difference. I have more energy throughout the day and sleep sounder. I actually look forward to the days on which I'll perform intermittent running (like today!).