I don't think people would ever carry their sporty clothes to hospitals in case of a test on a treadmill.
The release version makes it so that there are no outfit changes at all for the treadmill regardless of what patients are wearing, so technically they can still wear their athletic outfits for the treadmill if forced.
The beta (alternative) version makes it so that patients wear patient clothes for the treadmill if they are wearing something else, and after the test, they change into their previous outfits.