More intense cardio—like running, biking or jumping rope—works better with a little more space, but why waste the energy required to run a treadmill or stationery bike when the whole world is waiting for you? Lacing up a pair of running shoes and going for a jog is the simplest do-anywhere workout; all you need are the shoes.

If you're not a runner, you still have options. Hit your local hiking trails, take your two-wheeler out for a spin or just add a daily walk to your lunch hour.