Able-bodied people maintain their balance in part by the sensory feedback receive through our feet. People with severed spinal columns don't receive those sensations which, even though they are being supported by a mechanical exoskeleton, makes standing difficult. That's why a team of researchers at the Florida Institute for Human and Machine Cognition have begun teaching neophyte exoskeleton wearers to regain their sense of balance by standing atop a Wii U balance board.
Patients don't just stand there, obviously. They play games and run drills which require them to continually shift their weight. Over time, patients figure out how far they can lean in any given direction before tipping. This helps them redevelop their balance control despite the natural sensory feedback that they used to get from their feet.