Deep vein thrombosis (DVT) can happen when people stay still for long periods, typically sitting, and there have been several cases involving long-haul flights. It’s easy to see that certain games and consoles can lead to prolonged sitting and presumably the motion-controlled games are suitable antidote.
Chris was 20 when he died and DVT is easily avoided by short breaks and exercise, so it makes sense to highlight the risks to the millions of gamers out there. Microsoft also has a website, Play Smart, Play Safe that provides guidance to parents and gamers on a range of issues that can affect players.