Why medium medic can RUN as fast as LIGHT soldier or operetive. If MEDIC push the use button and try to heal LIGHT one.
IF light one is on the run, medic (medium) will folowing him on the same speed LIKE LIGHT one till can HEAL him. I think its realy BUG.

SOrry for my english.

Try it as a heavy buffing a light, rather amusing. It's just how they have the teammate buffing set up and happens with any class/body type. Holding the use button will have you get a speed boost and/or automatically find the fastest route to your teammate until you're within range to buff them.

There's a glitch where you can keep running at Light-speed (see what I did there?) as a Medium or Heavy just because they're trying to buff and can't catch up - it's meant to cut off after a short time without catching the person, but for some people, it doesn't, and they can keep super-speed forever if their target stays out of reach. It doesn't work very often for me, though.