Adapting to battlefield experience in Afghanistan and Iraq, the Army is revamping its basic training regimen for the first time in three decades by nixing five-mile runs and bayonet drills in favor of zigzag sprints and honing core muscles.

Trainers hope the switch will better prepare soldiers physically for the pace of combat, with its sudden dashes and rolling gun battles. They also want to toughen recruits who are often more familiar with Facebook than fistfights.