On ships a lot of stuff gets moved by hand. Subs take all their supplies on board by hand, and while it may seem mundane loading 4 months of food on board is a lot of physical work. In the squadron I was with the only time the Ordnancemen got out any power equipment to load a plane was when they were putting on 2000 lbs. bombs. Everything lighter than that was done by hand. If you have women doing those jobs you are going to need a lot more bodies.
Repetitive motion injury is one of the leading causes of non-combat injuries in the military. New technology may change that, though: