I've noticed when I run that I tend to lean forward. Been trying really hard to keep upright. Any one else do this?
Posture: I've noticed when I run that I tend to... - Couch to 5K
You are learning the new moves and waking up new muscle groups. You need to practice running upright, small steps trying not to overstride. And you need to do it slowly, that's how you'll get your posture and cardio in order. Ideally, you'd also be working on your core muscles, hips and glutes, all of which support your running and their strength can prevent injuries by protecting your knees through correct posture.