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What is Ground Contact Time in Running and Why is it Shorter for Experts?

What is “touchdown time”?

During running, one foot will be in the air, while the other foot is in contact with the ground. The two feet alternately touch the ground and take off, completing the action of running forward step by step. The time it takes for one of the feet to go from the moment it just touches the ground to the moment it completely leaves the ground is the ground contact time.

Taking this picture as an example, the touchdown time is the time from when the middle part touches the ground to when it leaves the ground.

In the cartoons we grew up watching, when the protagonist encounters an unexpected situation and runs quickly, it is similar to Tom in “Tom and Jerry”:

What it actually expresses is that the protagonist is running with a very alarming frequency. Therefore, it is visually exaggerated, as if the feet are “stepping” on Hot Wheels. Moreover, their touchdown time is also quite short at this time.

Generally, we use milliseconds as the unit to measure ground contact time, 1 second = 1000 milliseconds.

What is the significance of studying “touchdown time”?

Speed during running = cadence x stride length. The higher the running frequency and the longer the stride length, the faster you run. It seems like this is a very simple arithmetic problem. In fact, we will not blindly pursue high cadence and long strides – then we may not be able to run very far.

So what is the most reasonable way to run? This brings up the concept of running economy. There is a large amount of sports data surrounding running economy to study how people can run fast and effortlessly, including stride length, cadence, vertical amplitude, movement efficiency, ground contact time… and so on.

We found that the faster elite runners tend to have shorter touchdown times. If you want to increase your speed, shortening your touchdown time is a very important training direction.

The ground contact time is not an independent data. When you run, the shorter the ground contact time, it often means that the running posture is more economical. At this time, other data of the body will also be within a reasonable range.

How fast do top players touch the ground?

We use blink time for comparison.

Normal people blink 10 to 20 times per minute, and the duration of each blink is about 200 milliseconds to 400 milliseconds:

The ground contact time of professional marathon runners is often less than 200 milliseconds – that is to say, in less than a blink of an eye, professional marathon runners complete one contact between the sole and the ground while running (in addition, 200 milliseconds is also The time it takes for the human brain to recognize emotions in facial expressions is very short)!

Many people have intuitive feelings when watching the marathon live broadcast on TV. The top runners in the first group run their legs like motors, making it difficult to see the specific landing of each step – they are too fast.

Looking at top professional athletes, they seem to “run” step by step throughout the marathon. In fact, the total time their feet are actually in contact with the ground is very small, which is equivalent to “flying” close to the ground all the way. !

Here are the touchdown times for a group of world-record players:

When Bolt broke the world record in the 100/200 meters, the touchdown time was an astonishing 78 milliseconds. However, because the technical movements involved in sprinting are different from those in long-distance running, when used in the 100 meters, the touchdown time is not necessarily directly proportional to the performance. However, if the touchdown time of a sprinter is around 100 milliseconds, it is almost uncompetitive;

In the 400-meter race, Michael Johnson’s touchdown time was 80 milliseconds, which is also quite amazing;

In longer-distance running competitions, the touchdown time of “King of 10,000 Meters” Bekele in the 5,000/10,000-meter race is 130 milliseconds;

The half marathon world record holder, Zessene Tadesse, ran 21.0975 kilometers in 58 minutes and 23 seconds, with a touchdown time of 135 milliseconds – Tadesse is only 1.61 meters tall, so his winning formula is amazing Cadence and ground contact time are therefore also very short;

Marathon world record holder Daniels Kimeto’s average touchdown time when running a 42.195-kilometer marathon was 162 milliseconds, which is far below the 200 millisecond distinction line for elite runners.

So we can see that top athletes, whether they are long-distance runners or sprinters, have very short touchdown times. The longer the distance of running, the more the touchdown time is basically proportional to the competition performance;

The ground contact time of ordinary runners may be 300 milliseconds, and most amateur runners can reach a relatively good level of 220-240 milliseconds. The ground contact time of elite runners can be controlled within 200 milliseconds, or even reach 150 (or more). short) milliseconds!

It is difficult to see clearly with the naked eye the moment top players touch the ground and leave the ground;

Regardless of the length of a run, elite athletes do not push off the ground to create longer airtime.

Why does the shorter the ground contact time, the faster one runs?

Some people will ask, “Then if I quickly put my feet and legs in place and ‘run’ like a skipping rope, will I be able to reach the level of an athlete?”

This is a one-sided understanding of touchdown time.

The shorter the ground contact time, the longer it takes to airborne, which means more time is spent on “moving” the body.

Related to touchdown time, there is also the concept of touchdown to air ratio (touchdown time ÷ airborne time). The touchdown to air ratio of professional athletes is very small. Still based on the two distances between the full marathon and half marathon world records above, the touchdown to air ratios of Kimetto and Tadesse are 1.0 and 0.9 respectively.

If we want to run fast, we can’t just look at the ground-to-air ratio, but also look at whether our body is moving forward, or up/left/right during the time in the air – this is the scary thing about professional athletes. , they will control the vertical amplitude (that is, upward movement) to be very small, and their bodies will almost always move forward during the flight time. So every step they take is very efficient.

To describe it more exaggeratedly, it is as if a professional marathon runner has kept his torso almost at the same horizontal height for more than two hours, while his feet move quickly, contacting the ground very quickly, and moving steadily against the ground all the way. At the end. However, ordinary long-distance runners often feel like their legs and feet are heavy and sluggish in the second half of the race. At this time, the touchdown time (and touchdown-to-air ratio) often drops dramatically.

Therefore, for runners, when you achieve a short ground contact time, you can control the vertical amplitude as much as possible, avoid moving the body left and right/up and down, and allow the body to move forward as much as possible when it is in the air. At this time, your running It can be considered excellent.

Many runners are prone to bottlenecks in terms of physical fitness and muscle strength. At this time, if you focus on controlling the ground contact time with a little practice, your performance will often improve immediately.

How to shorten touchdown time through training?

What most directly affects the ground contact time is not your muscle strength, but your running posture and technical movements.

When you have problems such as stepping, pushing off the ground, or “throwing” your feet off the ground instead of pulling up…the time your feet are in contact with the ground will become longer, so we must first develop a correct running posture.

Another point is that the muscles of excellent runners are elastic. Targeted training of the Achilles tendon (such as skipping) will strengthen its elasticity, and the soles of the feet will bounce off the ground in a shorter time after touching the ground.

When you have strong lower body strength, you can often better control your muscles to run correctly. Many runners start out with correct running form, but then fail to maintain their running form after running for a while. Part of the reason is a lack of muscle strength.

There are too many knowledge points involved in muscle training, so I won’t go into them here. Remember that shorter ground contact time can only be achieved by developing good running posture, mastering correct running movements, and having sufficient muscle strength support.

Finally, let’s take a look at the running video of Kipchoge, the world’s number one marathon master:

Pay careful attention to the contrast between Kipchoge’s body and trunk (waist) and the horizontal line on the roadside. It is almost a straight line and rarely moves up or down. The contact between his feet and the ground is really very brief – the contact time of each step is about 160-170 milliseconds.