Both walking and running are excellent ways to improve cardio endurance, boost mood levels and help with weight loss. But as the miles add up, having the right pair of sneakers can make a big difference in performance, comfort and injury prevention.

Here, a look at the major differences between walking and running shoes, and how to purchase the right pair for your intended activity:

Walking and running might seem like relatively similar activities, but the biomechanics of each form of exercise is actually very different. When you run, there is a portion of the stride when both feet are off the ground. As your foot strikes the ground, the bounding motion of running places more force through the hips, knees and ankles, and the force of impact can be up to three times the actual weight of the body. Because of this and the variety of foot strikes runners have (heel, midfoot, toe), more support is often needed in certain areas of the shoe.

On the other hand, when you walk, one foot is always on the ground, and the impact being placed through the joints of the lower extremity isn’t as severe. Walkers also tend to use more of a heel-to-toe foot strike, which distributes the weight of the body more evenly.

Shoe manufacturers take these considerations into account when designing shoes for each activity.

If you’re looking for a good walking shoe there are a few characteristics it should have. The next time you’re shopping and trying on different models, here are four important factors to keep in mind:

CUSHIONING

Most running shoes have more cushioning in the forefoot and heel to counteract impact forces on the joints. This can increase the overall weight of the shoe and at times decrease the overall flexibility, which walkers need. However, with the minimalist shoe movement, there may be some running shoe models that are more flexible than traditional ones, have less unnecessary cushioning, and could work well for walkers. Just be sure they meet the other criteria on this list as well.

HEEL HEIGHT

Because stability and motion-control running shoes build up the heel to counteract overpronation, many running shoes have a heel that is raised higher than the toe. This is called the heel drop of the shoe and should be considered when looking for a walking shoe.

The recommended heel drop is 4 millimeters or less, and a lot of walking-only models have a zero drop. Some running shoe models can have as high as an 8-millimeter heel drop. Less of a heel drop makes the heel-to-toe walking motion feel more natural.

THE FLARE OF THE HEEL

Trail shoes and stability running shoes often have a flared heel. This is designed for midfoot and forefoot strikers and is unnecessary in a walking shoe. Walkers strike heel to toe, so a flared portion can actually get in the way of the roll through during the walking motion.

FLEXIBILITY

This one can be tricky, because both walking and running shoes need to be flexible. The difference is running shoes often flex in the midfoot or arch, while shoes that are good for walking should flex in the forefoot. This is because walkers push off with their toes for power, and the shoe needs to bend more in this area. Keep in mind any running shoe marketed as a stability or motion-control shoe will be less flexible overall and might not be a good option for walking.

Because of foot shape, individual needs, how flat or high your arch is and the amount of cushioning you prefer, what works for one person won’t necessarily work for another. Whenever you’re buying a new pair, it’s always best to shop in a specialty store so they can answer any questions you might have and let you try on multiple pairs to determine which one is best for you. Specialty walking and running shoe stores may also have a treadmill so you can walk in each pair and see how they feel. Keeping the above factors in mind, you should always choose what feels most comfortable.