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Time goal runners need to run faster, and this means some increase in stride length, greater bounce and foot pushing. By gradually increasing the intensity of speed training (with sufficient rest intervals and rest days between), feet and legs can adapt, but there is risk of injury. Be sensitive to your weak links and don't keep running if there is the chance that you may be starting an injury.

Posture is an individual issue. Most of the runners I've worked with find that an upright posture (like a “puppet on a string”) is best in all ways. When runners use a forward lean there is a tendency to develop lower back pain and neck pain. A small minority of runners naturally run with a forward lean with no problems. In this case, one should run the way that is most natural.