Like cross country skiing, the poles are used by the arms to match each step the person takes. Nordic walking increases your heart rate without increasing your perceived rate of exertion. You get a better workout without feeling like you are working any harder. While you can get a similar heart rate effect by walking faster, there are many people who do not want to walk faster or cannot walk fast. Nordic walking works the arms, shoulders and upper chest and back muscles through a full range of motion, stretching and lengthening those muscles which are often tight.
Many people exhibit stress by tightening their neck and shoulder muscles.
Nordic walking loosens up those knots. On any surface, the poles provide more stability for walkers who have balance knee or leg problems. Proper use of the poles and arm motion encourages good posture. People who had given up walking for pleasure find that they can walk comfortably with the poles. For natural trails, the poles provide stability for walkers much like a hiking stick.