It's very well designed and very smooth to use because it uses air resistance. The harder you pull, the more resistance you get. Keep in mind that this is not as effective as weight training and may slightly decrease the aerobic conditioning effect of your walking. However, if you move your arms in a variety of directions while walking, this is a good overall toning and aerobic conditioning exercise. Swimming, or a variety of movements in the water.
Water provides a great, low impact environment for exercise.
If you have access to a pool, this is another good option for aerobic conditioning and overall toning. So, if you're not a weight trainer, or perhaps you're taking a break from weight training, these are great exercises to help you incorporate overall muscle toning exercises into your aerobic workouts.