Walking and running differ in terms of calories spent and impact on your body. Finding equivalencies between the two depends on the walker or runner. While both are great workouts, your goals and abilities determine which is the more suitable exercise for you. Understanding the physics behind each will help you gauge how much walking is equivalent to running for your body.
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When all other factors are equal, running burns more calories than walking, because your body exerts more energy. Costanza Sol, with the Department of Exercise Science and Wellness Education at Florida Atlantic University, defines running as a small jump from foot to foot. Even though you propel the same body weight over the same distance with walking and running, when you walk, your body uses less oxygen, because it requires less energy to work against gravity. This means you have to walk longer distances to expend as much energy as you do when you run.
The American College of Sports Medicine journal "Medicine and Science in Sports and Exercise" reports how to calculate an equivalent calorie burn between walking and running. If you walk 3 to 5 mph, your calorie burn is equal to your body weight multiplied by .30 for each mile. When you run, your calorie burn is equal to your body weight multiplied by .63 for each mile. A 150-lb. person burns 45 calories walking a mile and 94.5 calories running a mile. By this standard, at all body weights, you have to walk 2.1 times the distance to burn the same amount of calories as running.
Walking and running put different amounts of impact on your joints. According to Sol, when you run each foot strike exposes your body to a force of two to three times your body weight. A 150-lb. runner endures approximately 60 to 90 tons of force on each foot during a mile, risking knee and other lower-body stress injuries. Walking, by comparison, is a low-impact exercise. This makes walking less likely to lead to injury than higher-impact types of exercise. It's a safe bet for many people in rehab or those who don't want to risk injury.
To further determine equivalency between walking and running, you must also factor in speed. Individuals have a preferred transition speed, the speed at which it becomes easier to run than walk. Researchers at The Zinman College of Physical Education and Sport Sciences found most people's preferred transition speed is about 4.5 mph. If you walk faster than your preferred transition speed, you'll burn more calories than if you ran at that speed, because you require more energy to continue walking at that pace. Most people can't keep up speeds higher than their preferred transition speed for very long.