Although it's disappearing little by little, I think there's still an impression in Fitness Land that you need to do traditional steady-pace endurance exercise to be considered "fit."

My take -- which I've explored in this book and this magazine article -- is that shorter, harder workouts should boost your heart health by making your heart more responsive to the most serious challenges you could impose on it.

Now a new study offers more evidence that sprints are at least as good as jogs for cardiovascular fitness (hat tip: reader Greg S.):

Short bursts of high-intensity sprints -- known to benefit muscle and improve exercise performance -- can improve the function and structure of blood vessels, in particular arteries that deliver blood to our muscles and heart, according to new research from McMaster University. ...

The findings support the idea that 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.

"As we age, the arteries become stiffer and tend to lose their ability to dilate, and these effects contribute to high blood pressure and cardiovascular disease," says Maureen MacDonald, academic advisor and an associate professor in the Department of Kinesiology. "More detrimental is the effect that blood vessel stiffening has on the heart, which has to circulate blood".

The research compared individuals who completed interval training using 30-second "all-out" sprints three days a week to a group who completed between 40 and 60 minutes of moderate-intensity cycling five days a week.

It found that six weeks of intense sprint interval exercise training improves the structure and function of arteries as much as traditional and longer endurance exercise with larger time commitment.

All the usual caveats apply -- small sample size, we're only looking at six weeks of training, the subjects were young and healthy (average age: 23.3, according to the study's abstract), etc.

Still, the advice to choose sprints over traditional endurance work is only given to people who're active and physically ambitious -- that is, willing to try something new and more strenuous in return for better and faster results. Age isn't a factor (I do sprints at 51, although sometimes I get halfway through the third or fourth interval and ask myself what the hell I think I'm doing), but fitness level is crucial. You don't just get up off the couch with no recent history of consistent training and start running sprints.

So the conversation about sprints vs. steady-state endurance training starts with a minority of a minority: people who exercise consistently and are willing to work harder in pursuit of more ambitious fitness goals.

Also worth noting: This study from the same research team at McMaster University, published in January, found that sprints and traditional endurance work produce similar metabolic adaptations.

The take-away message from these two studies -- assuming, again, that the study team's methods and conclusions are sound and apply to a broad population of healthy, fit people -- is that shorter, harder workouts get you to the same place as longer, slower ones. But they do it in much less time, and with three workouts a week instead of five.

That's great news for me, since I have no endurance whatsoever and have never been good at jogging. How about you?