All my life I've enjoyed pushing myself beyond limits that I thought I had. I was and still am an endurance freak thanks possibly to genetically larger than normal lungs. I ran, cycled, and played socker. All of this in addition to my Uechi practice. For the first fives years that I spent in the Army I consistently "maxed" the run in my PT test, running the two miles around 12 minutes or less without being winded. Unfortunately, my plica bands (extra tendons on the inside of a growing person's knee that are supposed to dissolve around 18 years of age) never dissolved and started causing serious pain. After surgery on both knees, the pain eased but, was always there. For years I tried to build my legs up using the standard weight training programs (3-5 sets X 10 reps - squats, leg press, etc.) but, never really got any real results. A couple months ago I read an article in Men's Health (I think) about a group of body builders in Florida who have been doing recearch on, what seems to be an endurance work-out, where the trainee works a certain muscle group every hour or half hour for several hours. And, that got me thinking...
Around that time, my knees were feeling especially painful. One day (Friday) I decided I was going to do something. I put 410lbs on my Bowflex and did 10 sets(10 reps) of leg presses. I started at 8AM. I noticed that I fealt stronger near the end. At 9AM I did it again and fealt even better. I repeated this until 5PM. The next day, the pain was incredible, but all in my muscles. But the day after that, I had no pain at all. No pain in my knees or muscles and I didn't have pain in my knees all through the next week. So, the next Friday, I did the work-out again. This time, I had no pain in my muscles and no pain in my knees. I'm starting to do this work-out with 200lbs dead lifts because I don't want to neglect the rest of my body. I can almost make it for the full 10 hour workout and have only rare and minimal pain in my knees. I actually gained almost an inch of muscle on my legs, which never came after years of standard workouts. So here's my question. Are these results possibly because I've trained my muscles for endurance for soo long, making it so that this type of workout (extreme endurance) is what will make them respond the best, or am I just some freak of nature?

This is the only resistance work-out I'm doing right now, which should keep me from over training. Any suggestions?