
Head
How you hold your head is key to overall posture, which determines how efficiently you run. Let your gaze guide you. Look ahead naturally, not down at your feet, and scan the horizon. This will straighten your neck and back, and bring them into alignment. Don't allow your chin to jut out.
Shoulders
Shoulders play an important role in keeping your upper body relaxed while you run, which is critical to maintaining efficient running posture. For optimum performance, your shoulders should be low and loose, not high and tight. Your shoulders also need to remain level and shouldn't dip from side to side with each stride.
Arms
Even though running is primarily a lower-body activity, your arms aren't just along for the ride. Your hands control the tension in your upper body, while your arm swing works in conjunction with your leg stride to drive you forward. Keep your hands in an unclenched fist, with your fingers lightly touching your palms. Imagine yourself trying to carry a potato chip in each hand without crushing it. Your arms should swing mostly forward and back, not across your body,between waist and lower-chest level. Your elbows should be bent at about a 90-degree angle. When you feel your fists clenching or your forearms tensing, drop your arms to your sides and shake them out for a few seconds to release the tension.
Legs
Efficient endurance running requires just a slight knee lift, a quick leg turnover, and a short stride. Together, these will facilitate fluid forward movement instead of diverting energy. When running with the proper stride length, your feet should land directly underneath your body. As your foot strikes the ground, your knee should be slightly flexed so that it can bend naturally on impact. If your lower leg extends out in front of your body, your stride is too long.
Feet
To run well, you need to push off the ground with maximum force. With each step, your foot should hit the ground lightly--landing between your heel and midfoot--then quickly roll forward. Keep your ankle flexed as your foot rolls forward to create more force for push-off. As you roll onto your toes, try to spring off the ground. You should feel your calf muscles propelling you forward on each step. Your feet should not slap loudly as they hit the ground. Good running is springy and quiet.
Reference: www.runnersworld.com
