I am a particular fan of integrative exercise - that is exercise that occurs in the course of doing some productive activity such as gardening bicycling to work doing home improvement projects and so on.
The working men I'll go by and they'll whistle. At first they whistle because they think 'Oh it's a girl. She's got blond hair and she's not out of shape ' and then they say 'Gosh it's Marilyn Monroe!'
