In reply to Thickhead:
> I'm sure some people can (and do) but I know I couldn't.
I think we would all agree that 8-11 is on the extreme end of the scale. When I used to commute into the office every day (work from home, or travel to other offices every couple of weeks now) then I could easily say that 8am-7pm was going to be dominated by work. A 45 minute run at lunchtime, or a run to work could be squeezed in though.
> but still managed a 5km run after with the collie.
That will do it! I've got a Collie too - wasn't going to run yesterday but he nagged me to go out at lunchtime - ended up doing a great 8km through the snow - was good fun.
> We exercise as a way presumably of controlling our mental state
I think this is key. Exercise is always portrayed as payment for some indulgence, and a means to an end. My primary exercise is running, and I do about 2000km a year mostly on trails. I do it because I love it, enjoy it, and the fact that it makes me very fit is a welcome side effect. I also love the fact that when I'm traveling on business, I can just bring my trainers with me and get out for a run in whichever city I'm visiting.
I also think that gyms are an easy place for people to convince themselves they're exercising when really they're just pottering around. My mother in law drives to the gym three times a week and forces herself through whatever machines they have in gyms these days, but constantly struggles with her weight. Despite living in a beautiful part of the countryside, the thought of going for a 30 minute walk every day seems alien to her (she's retired so time isn't an issue).