I started CF and the Zone in Dec. I weighed around 375-380 lbs. I am now 313lbs. I am following Starting Strength and am now strictly Zoneish/Paleo. My goal is continued fatloss while building muscle and strength. I completed the physical agility test for the Sherrifs dept. on Sat. I passed the test which is amazing in it self. Couldn't have done it 6 months ago. However, I was told by the administrator that I needed to work on my aerobic fitness if I am accepted. I am still a big guy at 6'2. I don't want to tear my knees up. I've been doing some sprinting along with walking. Will the sprinting do the trick? Am I being to impatient? Is there something else I can do or need to consider?