The first and primary reason to keep girls out of combat units is esprit de corps. Moral and the toughness of these units is based on a dynamic which woman destroy. Even if a women could compete phyically its a stupid idea for this reason alone.
Secondly minimum physical standards are just that. To give a somewhat dated example. When I was active the passing score for the PT test was 220. but in my division every infantry company had a gold Streamer for its guidon whick meant that 90% of the company scored 270 or better. (when you consider that nearly 10% would likely be on profile for some injury or on leave) meaning that every soldier could score the 270.. frankly nearly every soldier could do a max score.
Whats more the difficult physical test for a combat infantryman isn't running, pushups or carrying a buddy through an obstacale course. Its the wear and tear that body armor,90 lbs of gear, heat, bruises, bumps, rubs take over the course of a career. Every see a first sargent or CSM.. they are 35-45 years old and look 55-65. Its a hard abusive life, many (most) men can't do it and the % of women who can are far less. Even if they didn't destroy the Espirt de corps its not practical to find the small precentage of women who can hack it. Heck its hard to find the men who can.
Sure you could test for physical performance before enlistment, but its really a poor way to judge the longterm physical performance of an individual. Or should we send women through basic/AIT and then make a determination of their toughness.
