Often overlooked, the upper-body plays an important part in helping maintain good running posture. This is particularly true on longer runs. The more muscular endurance a runner has in the upper body, the longer he/she will maintain good posture delaying the onset of fatigue.
To do the exercise, grasp the handles of a resistance tube. Step on the center of the tube with both feet. Begin with your hands down by your thighs (1). Keeping the arms fully extended (no bend at the elbow), raise both arms straight in front of you until they are parallel with the floor (2). With controlled movement, lower your arms back to your thighs. Keeping your arms fully extended, raise both arms out to the side until they are both parallel to the floor (3). That's one rep. Shoot for 10-12 or 12-15 reps.
Tip: For more resistance, stand on the tube with your feet wider apart. For less resistance, stand with your feet closer together or just stand on the tube with one foot.
For more exercises for runners check out RunnerDude's new book Full-Body Fitness for Runners.