I wrote last time about the ongoing problem of breathlessness in our patients, with no organic cause beyond obesity. My usual response is to encourage weight loss by increased exercise – seems to be a winner, as exercise not only leads to weight loss, but it’s really good for us, right? And those patients who are breathless because they are simply unfit?

But how much exercise is the right amount of exercise to ‘prescribe’?

The government has guidance, so that’s a good place to start. 2.5 hours a week of moderate activity, in periods of at least 10 minutes. Or 30 minutes a day, 5 times a week.

NHS Choices agrees, of course, and gives more detail on what is moderate exercise, and what is vigorous exercise.

But last week the Beeb reported on a paper in the Journal of the American College of Cardiologists that too much exercise is as bad as none at all. Healthy joggers, and non joggers were followed up for 12 years. The conclusion was that 2.5 hours was the maximum that we should do, and if we are to run, we should run at a maximum of 8 kph. That’s 7:30 mins/km, or 12 minute miles. My 12 year old runs 5km in under 25 mins – that’s 5:00 mins/km, way to quick to remain ‘healthy’, according to the Danish study.

This isn’t the only study to support exercise being bad for us – Andrew Marr blamed his stroke on taking up rowing in 2013. And this week there’s a publication in Circulation looking at women in England and Scotland, their exercise regimens, and their cardiovascular risk. 4-6 sessions of mild exercise a week, or 2-3 sessions of strenuous exercise per week were deemed ideal. And anything more than that was deemed harmful.

I do a lot of exercise – I’m in a cycling club, I’m president of my Triathlon Club (not sure how that happened, I think I put my hand up at the wrong moment at the AGM), and I do about 8 hours of what these studies would call ‘strenuous’ exercise a week. All the people in the cycling club, and the tri club seem happy, healthy individuals to me, the occasional musculoskeletal injury notwithstanding. And I encourage my kids to be as active as possible.

But the data suggests moderation.

More to follow, I suspect.