Most efficient and practical cardio-vascular exercise session

With marathon boom happening in India, people are confusing passion with activities like long distance running being best for your health. It was in 2007, during India's first Ultra marathon held in Bangalore, where the maximum distance was for 78 km, I did 100 km. The race organisers could not comprehend triple digits and it didn't show up on their results page. But during first weekend of October 2012, an ultra marathon was organised around Bhatti Mines where twelve people had signed up for 100 miles.

I am very clear in my head that I run because I am crazy about it. So might be the case with folks who attempted 100 miles. From 3-4 such people in 2007, today we have over a hundred who would happily enter for 100 km race. In 2006, there would a few hundred who would sign up forna marathon but today I would imagine more than a lakh run a marathon every year.

But for maintaining health and health benefits from cardio-vascular exercise, it's shorter duration higher intensity exercise that is more important. I usually suggest people to have 30-45 minutes brisk. Now, there is evidence for the same.

Intensity versus duration of physical activity: implications for the metabolic syndrome. A prospective cohort study -- Laursen et al. 2 (5) -- BMJ Open
http://bmjopen.bmj.com/content/2/5/e001711.full