Power armor has been a concept since well into the early 1950s when Starship Troopers the novel came out. Its abilities and sources have all but begun to enter the real world everyone from DARPA to the Japanese have begun making power armors.
The powered armor of sci-fi is mixed, specifically on what the operator of the armor will be wearing while donning the suit. Some works believe that future armored soldiers would ride into battle in their normal BDUs, like in Avatar inside the AMP suits, others believe that specialized interface suits would be worn, like those seen in Crysis 2, still others project the use of liquid cooling and ventilation garment like those currently worn by astronauts during EVA operations. Then lastly, we see some works project that the operator of a military power suit will be in their lingerie or even naked, as we witnessed at the end of some early Metroid games. Some of this can be attributed to the carnal desire of humans and geeks, but it could be based in reality. The neuro-network could function more effectively with direct contact to the skin just like the main halo protagonist Master Chief. The Chief is naked under the MJOLNIR armor and we all see how fluid the Chief's movements are. Of course there is a major advantage of a user being naked under the armor the suit can literally access every muscle and nerve ending of the user. For my own stories the ISMF and naval special operation use the Scorpion Mk3 power armor which is normally worn over a specialized but not over the top BDU. The suits enhance the wear by 2 in categories of strength and 1.5 in speed. Its nothing major but most of the NSO can lift twice their body weight with ease.