Someone posted a nice video of the Sarcos exoskeleton; unfortunately, I can't tell how old it is. However, it's informative and the exo is cool, so take a look.
(Sarcos exoskeleton video)
Two-hundred pound pulldowns are easy; you can lift 70 pound ammunition cases endlessly. You can run in the suit, and walk up stairs, all carrying heavy loads.
Although the model shown in the video is tethered by power lines, future models will carry battery backpack power. The Sarcos exoskeleton is also designed to carry on without its human wearer in an autonomous mode. Also, the company is designing the exoskeleton with different kinds of armored coverings.
Robert Heinlein discussed this idea with lots of details in his 1959 novel Starship Troopers; read what he has to say about a powered suit:
The real genius in the design is that you don't have to control the suit; you just wear it, like your clothes, like skin.
The secret lies in negative feedback and amplification.
Here's how it works, minus the diagrams. The inside of the suit is a mass of pressure receptors, hundreds of them. You push with the heel of your hand; the suit feels it, amplifies it, pushes with you to take the pressure off the receptors that gave the order to push.
(Read more about Heinlein's powered armor)