Once I started doing some free weights exercise, I got the unexpected bonus of enjoying other physical activity a lot more (or at least disenjoying it less), because it became less tiring. I found I would spontaneously do things like sprint up the metro escalator or several flights of stairs, without being winded when I got to the top.

I do kettlebells; more conventional free weights may or may not produce the same effect, though I started with the latter..