August 05, 2021 TOPICS

Research shows the optimal fast walking speed to increase calorie burning efficiency is 7 km/h

The results of a recent study have shown that walking consumes more energy than running if you can maintain a speed of at least 7 km/h. In addition, fast walking (also known as speed walking) causes less shock to the feet than running, which reduces the risk of injury and sports anemia. With telework becoming the norm and people working longer hours at home, could walking 7 km/h be the silver bullet for calorie burning, dieting, and physical fitness?

[Key Points of this Article]
● Explains the difference between fast walking and slow jogging
● Describes cases where walking consumes more energy than jogging
● Shows that speeds above 7km/h are not economical for the body
● Explains how the key to keeping up a fast walking habit is interval training
● Shows how reduced impact on the soles of the feet helps prevent sports anemia
● Shines a light on the suppression of the hunger hormone ghrelin

“Inefficient” fast walking increases weight loss

Fast walking and slow jogging are gaining popularity as an easy way to lose weight and improve health. But which is more effective in terms of impact on the body, calorie consumption, and exercise? To answer this question, we spoke to Professor Kazunari Goto, a sports and health science expert in the College of Sport and Health Sciences at Ritsumeikan University,

He explains: "For example, jogging at very slow speeds of 3km or 4km per hour consumes more energy than walking at the same speed. In jogging, each step involves a jumping motion, so you probably think that jogging is more tiring.
So, what happens when you gradually increase your speed?
In fact, it turns out that once you reach a speed of over 7 km/h, walking consumes more energy than running at the same speed.
More energy consumption means an activity is less efficient for the body. If you actually try it, you will find that running feels easier to do than walking at around 6 or 7 km per hour. Just as cars get better fuel efficiency when driven at the right speed, there is an appropriate speed range for both walking and running for humans.
However, from the point of view of calorie consumption and weight loss, it is more beneficial to use more energy. Fast walking was conceived to take advantage of such inefficiency.”

Two types of muscle fibers are mobilized when walking fast: Fast-twitch and slow-twitch muscles

Let's take a look at the results of Professor Goto's experiment from the figure below. The characteristics of energy consumption during fast walking are clearly visible in the data.

For this study, eighteen men and 18 women in their 20s walked and ran, and their energy consumption was measured in terms of oxygen intake and carbon oxide emissions.

"When you are running, your energy consumption increases linearly as your speed increases, whereas when you are fast walking, your energy consumption increases exponentially after a certain point. I believe this is due to the fact that you can't walk as fast as you can run, but when you try to force yourself to walk, it creates a ‘distortion’, so once you cross a certain point, your energy consumption increases all at once.
The data also showed that your body uses a great deal of glycogen at the point where your energy consumption increases rapidly. Glycogen is a type of sugar that is stored in large amounts in our fast-twitch muscle fibers. During normal walking, you mainly use your slow-twitch muscle fibers, but the data from this study showed that your fast-twitch muscle fibers are also mobilized at around 7 km/h,” explained Professor Goto.

What this means is that when your body starts to mobilize both your slow and fast-twitch muscle fibers, your energy consumption begins to increase rapidly.

6 sets of 30-minute intervals: An easy way to make fast walking a habit

By the way, what kind of speed is 7 km/h? In terms of pace, it means walking one kilometer in 8.5 minutes. If you try walking while measuring the speed with a smart watch or other device, you will see that this is quite a fast pace. So, what is the key to effectively incorporating fast walking into your daily life?

Professor Kazunari Goto (College of Sport and Health Sciences, Ritsumeikan University) /Source: Asics Stories

"The average speed of fast walking for a man is about 6km/h. I recommend that you gradually increase your speed, rather than aiming for 7 km/h right away. Also, 7 km/h is just a guideline, so you don't have to stick to that speed the whole time. You should just try to walk as fast as you can. If you are not in the habit of exercising much, 6km/h is fine, and if you are obese or elderly, there is no need to stick to 7 km/h.
I also recommend using interval training when walking. Walking at 7 km/h for 30 minutes is quite a workout. Using intervals, where you alternate between fast and slow walking, is not only practical, it’s an excellent way to get in shape.

The interval training we are currently using in our research is 5 minutes per set. You walk fast for 3 minutes and slow for 2 minutes. If you do six sets of this, you get a total of 30 minutes,” explains Professor Goto.

Timer apps for interval training are readily available. Walking is more effective than jogging, so why not make it a part of your exercise routine?

Reduce your risk of sports anemia and curb your appetite!

The benefits of fast walking are not limited to calorie burning efficiency. Fast walking is not only an effective way to burn calories, it also reduces the impact on the soles of the feet and the stress on joints and bones.

"Some people who run on a regular basis may suffer from iron deficiency due to hemolysis, a condition in which the impact on the soles of the feet destroys red blood cells. However, because walking places much less force on the soles of the feet than running, there is less stress on the knees and other joints and bones, not to mention a lower risk of hemolysis. Fast walking allows you to burn more energy at a higher load while reducing the risk of iron deficiency and sports anemia,” says Professor Goto.

What’s more, recent studies have shown that exercise can suppress appetite by reducing levels of the hormone ghrelin.

Professor Goto explains: "The hormone ghrelin, which increases appetite, is found to decrease rapidly after a long period of moderate intensity exercise. When you exercise, blood is supplied preferentially to the muscles, which in turn suppresses the flow of blood to the digestive organs such as the stomach and small intestine, which are not considered to be directly related to exercise. As a result, the amount of ghrelin secreted from the stomach is suppressed, and this is believed to result in appetite suppression.
Ghrelin also plays a role in stimulating the secretion of growth hormone, but since a large amount of growth hormone is produced during exercise, the need for ghrelin is reduced. As a result, ghrelin secretion is suppressed along with your appetite. Fast walking is more intense than regular walking, so you can fully expect a decrease in ghrelin from exercise.”

Making a habit of exercising with a certain level of intensity, such as fast walking, may help reduce overeating. Perseverance is power. Fast walking, which is easy to continue and highly effective, seems to be an ideal exercise that anyone can easily take up amid the ongoing pandemic, during which exercise levels have chronically declined.

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