Physical Danger
As the manager of the team, you basically get to shout all day from the comfort of the bench, and no one can tell you otherwise. Since everyone else is doing all of the actual athletic stuff, you should be okay.
There are the occasional objects that make their way into the dugout, sometimes traveling at supersonic speeds. Such objects include foul balls, pieces of broken bats, errant throws, players trying to dive for a foul ball, or even the odd bird strike—and they often happen when you least expect them.
Also, watch yourself on the dugout steps. You don't want to be the guy who falls down the concrete stairs on live TV.