Partly because of its supposed effectiveness in countering stress, spending moderate amounts of time at the gym falls within what I consider acceptable procrastination. It certainly helps that the Hart House gym has pretty good hours and is only a four minute walk from my bedroom (as well as the libraries where I should generally be embedded for the next month).
Generally, I do 25 minutes of cardio on an elliptical machine, run a lap, do another 25 minutes of cardio, run another lap, and then row for 2000 metres. Even with my new glasses, I don’t find that I can effectively read during any of these activities, so it’s also a chance to catch up on Planet Money, This American Life, The Current (I tend to avoid the most depressing stories), and the Savage Lovecast (abrasive, but a useful source of perspective – like his long-running column). I wish Stephen Fry released his podgrams much more often (the one on language is wonderful, and an antidote to pedantry).
When working on exceptionally daunting and unpleasant tasks, I have to suspend the rules of my normal procrastination flowchart, since following it would easily allow me to cut study time to nothing. Beyond the gym, a few forms of acceptable non-study activity include corresponding with friends and family members (though I am still well behind); dealing with especially time-sensitive 350.org tasks; purchasing, cooking, and eating brain-sustaining food; taking and posting photos of the day; and doing a quantity of paid work that reduces the rate at which my savings are depleting.
Less justifiable activities that sometimes sneak in are the occasional ladder game of Starcraft II (seems to raise wakefulness as much as a large cup of coffee, without insomniac side-effects), reading materials unrelated to the comp, and ongoing endless correspondence with the Canada Revenue Agency.