You can definitely push military personnel harder--NFL players are unionized, service members aren't, and law and society wouldn't look very kindly on any private enterprise doing some of the harsher things seen in military training.
For an extreme example, consider SERE (Survival, Evasion, Resistance, and Escape) training. This is an extensive course intended to prepare personnel for everything that can go wrong behind enemy lines--how to survive off the land when separated from friendly forces (downed aircrews, for instance), how to evade capture, and what to do when one is actually captured (the "resistance" and "escape" portions). While the early portions of the course cover comparatively "fun" subjects, the later portions involve being subjected to captivity and abuse. The intent is to train people to resist torture and escape from enemy POW camps.
For an extreme example, consider SERE (Survival, Evasion, Resistance, and Escape) training. This is an extensive course intended to prepare personnel for everything that can go wrong behind enemy lines--how to survive off the land when separated from friendly forces (downed aircrews, for instance), how to evade capture, and what to do when one is actually captured (the "resistance" and "escape" portions). While the early portions of the course cover comparatively "fun" subjects, the later portions involve being subjected to captivity and abuse. The intent is to train people to resist torture and escape from enemy POW camps.