One of the most effective exercises to strengthen our body: PULL UPS.
Pull-up bars require very little space, though the greater the open space, the better the feeling while actually exercising.
I have this installed at my studio, right above my desk space. That's right the Mississippi Earrings studio has that sort of space, thankfully. Whenever I feel like, I spring up, jump and do a few pull ups. Has helped me quite a bit.
If you are in Ahmedabad, and planning to drop in at the studio, you can check it out.