The Simulator is a USS Academy equipment exoskeleton that allows one to fully immerse one's consciousness in a virtual reality.
A Martial Arts simulation that works as a "neuro-interactive" interface which means that information is directly fed to the human brain where the environment the Simulator creates a person's sensory perception resulting into a flawless illusion indistinguishable from reality for those connected to it.
The manner in which the exoskeleton works has not been described. However, it is plausible that it includes low frequency transmitters that incorporate small electronic memory buffers that retains the subjective appearance used by the "avatar", allowing the human to retain certain physical characteristics. Communication is probably a mixture of electrical and electromagnetic transmissions, where the exoskeletob is the central interface, with perhaps thousands of tiny connectors or electrodes that are woven through the central nervous system. It also involves the incorporation of various sensors that continually monitor blood pressure and brain waves allowing those monitoring to provoke a safety logout if they see fit.
The system was designed to inflict real damage on the human body. The breathing apparatus is used to change the atmospheric pressure of wearers environment for example changing the atmospheric pressure to .7 is like having a training session at 3,000 meters (9842 feet) in altitude. In addition the exoskeleton itself can be constricted to not simulate joint locks. So in addition to the highly sophisticated neural interface that makes physical attacks feel real making even death a possibility the device can be used to crush bones and rip ligaments. So not only can the USS Academy Simulator be used to teach various combat styles but train in combating tem as well.