American Parkour

Mostly because I don't like asking my parents for help...

Anyways I've been working a lot on my rolls this summer. Recently (August 3rd or 4th) my town had a festival and I got really worked up dancing and ended up jumping off a 10-12 foot fence. I've been able to still do Parkour since then, and I've had no trouble walking... but my legs have only gotten increasingly sore and now they feel sore almost all the time. It's not a stabbing pain, just an aching one. I assume because it's just an aching pain that theres no need to go see a doctor. How should I get back to Parkour as quickly as possible without visiting one?

Date of Injury: 4/05/08
Time of injury: ~12:00-14:00
Age: 17
General Location: Suburbs of Chicago
Total time training: Half a Year Indoor Training
Hours per week: Used to be 2-3, now about 1 hour of training a week
Other Exercise: I don't get much exercise anymore as I am a high school "graduate"
Location: ~6 foot tall brick wall behind a friend's house over grass ground.
Conditions of location: Fair
What I Was Doing: I climbed over the wall about 20+ times that day, and I decided to try working on topping off cat jumps. I would pop up and try to support myself by twisting my arms below me and catching myself. I never actually successfully did this.
Other People Involved: A few people watching, but no one else who knew a large amount about Parkour.
Part of body: Inside muscles on left elbow
Did you see a doctor for diagnosis: No.
Did you get X-rays or MRI's: No.
Picture of the injury: N/A
Could you / how could you have avoided the injury: By not trying to train a maneuver I had never been capable of in the past. In other words, by not trying to show off.
Date / type / severity of your last injury: Decemberish I had a small wrist injury in my right wrist due to attempting a kong over two trashcans that I was incapable of. My shoes were wet which caused me to slip harder when I fell out of the attempt. The wrist injury got increasingly worse over the following few days, then disappeared only to resurface months later while play-fighting a friend of mine.
Notes on the experience: It was my first day back in warm weather since I had begun training and I most definitely should not have been training on this day in front of other people. I began learning about Parkour right before first frost, and had little to no previous outside experience.

Does anyone know which is better for our bodies as far as Parkour goes? I studied classical guitar very intently for about 2 years. The whole time, every teacher I studied under (and I studied under some of the best classical guitarists there are) would tell me that relaxing my muscles was the only way to prevent injury (mostly tendinitis, but there were some other ones, including one that could lead to you not being able to use your hands ever again). However, I went to an art school during some of this time, and there was a dance department there. One day my classical guitar teacher talked about the dancers. He said that alternatively, dancers had to keep every muscle in their body tight, and keeping their muscles tight was the only way to achieve what they wanted too. Our quality got better with relaxation, their quality got better with tension. So where does Parkour lie on this? When I'm doing a roll or a vault, or a landing, or whatever, do I want to pull every muscle in my body tight, or do I want to relax them and let my body just flow? Is it a mix? I imagine you have to pull your muscles fairly tight in some areas while leaving them relaxed in others. If I'm wrong, I'd love to know now, so I don't go about this the wrong way. :-)

Today I tried my first roll on concrete and it hurt my spine a bit. I think it's because I'm really skinny and my spine sticks out a little bit when I bend over. Has anyone had a similar issue and have any advice on how to not hurt myself in the future?