Lets say you lived in a gravitational experimental room

With the insane amount of pressure and harm it'll cause on the human body, which would probably cause a TON of health issues and physical ailments, aside, IF a person were to undergo "testing" under higher gravitational pulls for long amounts of time, then yes, they would be significantly stronger and be able to perform higher amounts of feat that a normal human being.

However, such an experiement in real life would cause more harm to the human body than good. In fact, it might even kill a person before they can "test" anything.