If you ran one mile, would you have burned the same number of calories as if you had simply walked?

Intuition tells us that, for equal distances, running requires more energy than walking and therefore burns more calories. After all, running is a lot more sweaty and uncomfortable!

But …does it?

In order to find the answer, we need to define three important terms and understand how they are related.

The first is Energy. In physics, energy is the quantitative property that must be transferred to something physical in order to perform work on it, or to heat it. A less descriptive definition of energy is “the ability to do work.”

Visualizing energy is elusive, like an invisible force that can change into different forms, but most of the time the presence of energy can be visualized when the transfer occurs. For example, if you burn firewood, the invisible chemical energy in the wood is converted to heat energy, which you can see as fire. With regards to human movement, energy moves through our muscles, joints and bones.

The second is Work. Work is the energy transferred to or from an object via the application of force along a displacement (distance). In its simplest form, it is the product of force and displacement: W=F*d. So, think of work as “energy in action.”

Work and Energy have the same unit, called a Joule, which is the energy required to move 1 kg a velocity of 1 meter/second. So, when you walk one mile, your musculoskeletal system is performing work (W) by moving the weight of your body (F) over one mile (d). Weight is a force, as it is the mass of your body x gravity (acceleration).

The third is Calorie. In food science, one Calorie is the amount of heat needed to raise the temperature of 1 kilogram of water 1 degree Celsius; hence the phrase “burning” calories. Foods that we eat contain calories, which are represented by the energy stored in the bonds of the atoms of carbohydrates, fats and proteins. One gram of fat contains about 9 calories, while one gram of carbohydrate or protein contains about 4.

Calories are important to us because they are central to fat (not water) weight gain and loss. With the overabundance of high-calorie foods, weight loss is a concern for many. And along with calorie restriction (dieting), exercise is the means by which people try to lose weight. Exercise requires energy and work, which in the human body is sourced from calories. For those wanting to lose weight, the calories that are desired for burning are not in the food from a recent meal, but rather in the bonds of stored triglycerides; i.e. fat cells. Those unwanted fat cells are the result of the surplus of calories consumed (more than your body needed) over years and years.

People wanting to lose weight are interested in the best forms of exercise that will help them burn calories and use up those unwanted fat cells.

Before we address the original question of whether or not running one mile burns more calories than walking one mile, lets first discuss the two, main approaches to exercise: cardio and resistance.

Cardio exercises are exercises that result in sustained, increase heart rate. They are characterized by continuous movement of the body. Examples include running, walking, cycling, and the many types of aerobics classes such as cardio kickboxing. The continuous movement of your muscles in cardio exercises, when done for over 20 minutes burns fat and strengthens the heart muscle. A stronger heart is able to pump more blood to cells and increase cardiovascular endurance; hence the name.

Resistance exercises emphasize placing resistance on the large muscle groups, i.e. the legs, arms, back and core. They force the muscles to generate power, which burns calories just like cardio exercises. The resistance can be weights, resistance bands, or the weight of your body (squats, planks, pull ups, crunches).

This brings us to the calorie-burning effects of running vs. walking. Let’s say Tom, who has a mass of 50kg, walks one mile in 12 minutes, then runs a mile in 8 minutes. Did he burn the same amount of calories in both miles?

Since Work=Force x Displacement, the work Tom generated in both cases was as follows:

Force=mass x acceleration (of gravity on Earth, in this case)
Force=50 kg x 9.80 m/s2 = 490.33 Newtons (the unit of force)
Work=490.33 N x 1609.34 m = 789,107.68 Joules = 789.108 kJ

Since 1 calorie is approximately .239 J, Tom burned about 188 calories walking, and another 188 calories running because in both cases, he moved the same amount of force (his body weight) over the same distance…

THEORETICALLY.

The human body’s use of energy is not as easy to calculate compared to a machine. There are many variables in human movement; particularly in the way the muscles are used.

Let’s address the critical factor that will help us answer the original question – the biomechanics of walking vs. running. Do they use the same muscle groups in the same way? Do the muscles perform more work in one vs. the other given the same distance displaced? Is energy use the same in both?

I propose that energy expenditure in running is significantly higher than in walking, and here’s my argument.

If someone walks a mile in 12 minutes, then runs one in 8 minutes, it is conceivable that he burns the same amount of calories each time, because although running burns more calories per unit time (there is more muscle twitching with running), it is over a shorter time than walking. It is sensible that walking that extra four minutes makes up the balance.

Let’s make the comparison even closer: suppose Tom walked a mile in 12 minutes and “ran” the next mile in 12 minutes as well. This can be done at a certain threshold—the point (speed) where one can still walk fast or run at a light pace. It is best realized on a treadmill, because you do not change the treadmill speed but can either walk fast, or use a running movement. You’ll have to try it to know what I mean. For me, that threshold is 4 mph. I can switch between walking fast and running at a light pace. In this scenario, the times for completing both miles are equal (walking one mile in 12 minutes, then running one mile in 12 minutes), which makes the question of which burns more calories more interesting, and definitive.

Have you tried to figure out what specifically changes when you switch between walking fast and running? Lately, I’ve been speed walking a mile using a treadmill and running a mile, at the same pace, and tried to sense what was happening as I switched between the two.

Here’s what I discovered:

• I immediately sensed that running made me breathe harder.  An increased respiratory rate from exercise signifies a higher metabolic rate in the muscles (more glucose being used up in the citric acid cycle, which demands more oxygen).
• Running felt harder to do than walking fast. This is evidence that I was expending more energy running than walking.
• My strides were the same running vs. walking. In other words, I was not taking more frequent, shorter strides during running; they were about the same length.
• I was bobbing up and down more during running. This was evident from my visual field—I noticed a significant increase in the vertical up and down movement of objects I focused on (the treadmill faced an open window, with trees in the distance). I estimated it to be about 2-3” every stride.
• I sensed more muscle expenditure in my lower leg (calf) muscles and foot muscles when walking, compared to running.
• I sensed more muscle expenditure in my upper leg (quadriceps) when running; i.e., stronger contraction in my legs compared to walking.

My conclusion is that, although fast walking and light running were done at the same speed, there were differences in the biomechanics of the movements. Unlike walking, running involves a subtle vertical push upwards, generated mainly by the quadriceps muscle starting at the heel strike phase (leg forward position, initiation of propulsion) through the mid stance to toe-off , that lifts the entire body up about 2-3 inches, compared to walking. This was evident even as I tried my best to stay level while running.

So, my theory is that running a mile burns more calories than walking a mile, and the extra work/ calorie burning in running comes from the stronger concentric contractions (meaning, more muscle fibers firing which uses more glucose) in the leg muscles to generate that extra vertical height against gravity PLUS the stronger isometric contraction that occurs when landing from that extra height, from heel strike to mid stance. So, switching to a running gait gives you a double whammy of calorie burning over walking, even when doing it at the same pace and over the same distance as walking.

Another way to look at it is potential energy. In physics, potential energy is the potential energy associated with gravity, which is released when the objects fall towards Earth. Hydroelectric power comes from the potential energy of water stacked high by a dam, and released at a lower level. The movement of water due to gravity is harnessed by the generator, which produces electricity.  This is also a good example of how energy converts to different forms; from potential to mechanical to electrical.

Potential Energy = mass x gravity x height (above ground). When you run, because the biomechanics causes your whole mass to rise 2-3” higher than when walking, potential energy builds up and then releases, which travels through your muscles and bones as a force that needs to be dampened by muscle contraction (or you would collapse), which burns more calories.

So, if you were told that walking a certain distance burns the same amount of calories as running the same distance because of the formula W=F*d, where F and d values are the same in both cases, it’s likely not true. The faulty assumption here is that your body mechanics are the same when they are not. Running 3 miles feels you are doing more work because you are. Your heart rate is faster (this alone burns additional calories), your muscles and joints ache more, and your breathing rate is higher than if you walked the same distance. It’s all because with running, you are expending more energy elevating your body an extra 2-3” with each stride. This effort requires more calories in generating that lift, and absorbing it.

So yes, running is a great cardiovascular exercise to burn calories and lose weight. It does place more stress to your joints, so make sure you can handle this; otherwise, you are better off walking for exercise. But, you will need to walk a greater distance to burn as much calories as running, so it’s going to take you more time to lose weight with walking, compared to running.

If running is just too uncomfortable for you, try speed-walking because ultimately, any movement is better than none when it comes to staying fit and maintaining a healthy weight.

Nicola TL, Jewison DJ. The anatomy and biomechanics of running. Clin Sports Med. 2012