Physical Danger
As long as you don't get stuck deciding which of two murderous, revenge-driven serial killers deserves $50,000 of the other's money, you're probably going to make it unscathed to arbitrator retirement. Sitting in a small conference room or court all day, reading paperwork while listening to people argue, just isn't that dangerous.
Of course, there are many documented dangers of living a sedentary lifestyle, though we're envisioning you as the active arbitrator—walking in and out of courtrooms with purpose while carrying a heavy but stylish briefcase. Work those biceps in style.
So yeah, just make sure to move around a bit between arbitrations and you'll be fine.