I used to play foot ball (by which I mean "soccer"), and so ran about 40 miles a week. I was still a big fat ass though. I learned about lifting weights at a pretty "serious" Florida gym. I did that on and off for years, getting "big" and "small" (but always fat). I lost a bunch of weight a few years ago, and slowly gained it back. Atkins was too boring to keep up forever. Now I'm on the pizza and beer diet, where I eat about 1500 calories worth of pizza and beer in a day. And I drink lots of water and eat my vitamins. And I lift weights, do squats, and 100 sit ups on an exercise ball every 3 days. I do interval training (with a standup bike) the next day.
That routine gives my muscles enough time to heal between sessions. They always hurt like hell on the second day after a work out, but they suddenly feel better on the third day -- the next workout day.
I used to go crazy with the weight when I was in high school. After a lot of foot ball, my legs were pretty strong. And then I started doing squats, and was able to inline squat like 850 pounds a few weeks later. It was pretty sweet when a buddy and me both kicked a soccer ball simultaneously and hard, Rasengan + Chidori style, and I flipped him end over end, as he was airborne and my foot pushed his backwards. Also, it's kind of fun to walk fast while you're in downtown Portland, and then accidentally JUMP three feet into the air Mario-style because the person in front of you suddenly stops for no apparent reason (and slamming your foot down instead of stepping is the only way you can stop). I got funny looks that day.
I would put on an extra five pounds of weight on my bench presses every week. That's fast... people would tell me to be careful. And they would end up carrying a bit of weight if they spotted me, but I always made it to 15-12-8 reps without help (while going for 8-to-failure as a goal) or even 15-12-8-8 reps. The rationale for that breakdown of sets is to tire your muscles out quickly in the first and middle of the second set, so you are in "failure mode" for something like 16 to 24 reps. It's TOUGH to push or pull in that state. Your muscles aren't even tired so much as your brain is tired of signaling your muscles to push or pull. This is why people strain when they lift: their nervous systems are trying to find new muscles to signal to in order to lift the load. Making "new connections". It's like learning how to roll your tongue or wiggle your ears. http://www.wikihow.com/Wiggle-Your-Ears Straining is like the "experiment" part. With a little practice, you can lift the same load with less effort. You will "know how it feels", and so can focus your concentration on it instead of wasting effort (and brain chemicals) on straining.
Strengthening the nervous system is an important part of strength training. Probably the most important part. At least if you want to get strong. There are better things to focus on if you want to get big.
I have always hated cardio workouts. Too boring. Sport can be an exception, if you at least have to put your mind to work to win. I hurt my ankle pretty badly in college, so I haven't played any team sports for a long time.