I'm new to this site and I was wondering if anyone would have an answer for me. I've recently found out that I have stress fractures in both of my legs (my tibia) and I can't run for the next 4 weeks. I'm training to get my 3 mile down to about 21 mins because I'm trying to get into the OCS program for the Marine Corps (Officer Candidate School). I was wondering if anyone knew if I would be able to swim or do any other sorts of cardio workouts in the mean time? I tried getting a hold of my doctor several times but he's taking forever to get back to me and I'd like to get back to doing cardio as soon as possible!