Yesterday I was in pole dance class talking to one of the other girls and she told me that not only does she do no other exercise apart from pole but she trains at least four times a week.
It struck me that for most people this is a terrible idea. Not only do you only work a few specific muscles very hard (she does have amazing abs) and neglect others but it must also be exceptionally boring. And I say this as someone who really loves pole dancing.
One of the foundations of microeconomics is convex preferences, which basically says if I like A and I like B then I prefer a mixture of A and B to just A or B.
For those straining your brain to remember their undergrad economics courses this is a slightly fancy way of saying we have diminishing marginal utility: as we consume more of just one thing we get a bit bored and we don't like it as much. Which will eventually mean you don't really want to do it at all and is why it's important to keep your exercise schedule "non-routine".
I do a mixture of running, yoga, circuits, dancing and parkour. Which not only provides a nice balance meaning that my body gets a good overall workout, but also that I continue to love everything I do!