Ive been doing the treadmill for 3 months now and my cardio kept improving, today I went running in the park for the first time and after 10 minites i was feeling
and now my legs hurts
what the hell is happening brehs?



Man up and keep running. The treadmill softens the blows and impacts on your knees.
A couple of questions.
Height? 6'1
Weight? 241
Experience running? been running for 3 months (treadmill)
Running on pavement, particularly with shytty shoes, will give you shin splints. Ideally you want to run barefoot (no I'm not joking) somewhere grassy if possible - if not, at least get proper running shoes.
If you can run barefoot safely then you definitely want to, you'll run longer and its much easier on your legs.
As an aside, there is a pretty interesting book on the subject of barefoot running that you might like...
http://www.amazon.com/Born-Run-Hidden-Superathletes-Greatest/dp/0307266303
Running on pavement, particularly with shytty shoes, will give you shin splints. Ideally you want to run barefoot (no I'm not joking) somewhere grassy if possible - if not, at least get proper running shoes.
If you have been running in tennis shoes your entire life, suddenly changing to a very minimalist shoe or straight to barefoot is going to be painful and cause injuries.