Article updated on October 7, 2020
Sometimes it seems like you don't know what to do to run faster, to improve, to achieve a personal best. You can get dizzy doing intervals to the maximum of your own ability. You can also exhaust yourself (and have fun) on long rides to try and improve your endurance. On the other hand, one of the factors that we do not work often and which is correlated both with a more efficient running technique and with better results in running, is the time of contact with the ground. Indeed, in general, the best runners touch the ground for less time than the less good runners.
What is Ground Contact Time (TCS)?
The term is relatively clear, ground contact time is the time, usually expressed in milliseconds, that a foot is in contact with the ground. For example, if you run at 180 steps per minute, you take 3 steps per second on average, so 333 milliseconds per step. If you have a ground contact time of 111 ms, that means that out of the 333 ms of a step, you are on the ground a third of the time. If you are on the ground for 222 ms, you are on the ground two-thirds of the time. The easiest (though not that easy) way to assess your ground contact time is to film yourself from the side with a camera filming at high frequency. You can then estimate your ground contact time.
Why is it advantageous to have a shorter TCS (Ground Contact Time)?
If you are on the ground for less time, it is because you are in the air longer. When you are running the fastest time is when you are in the air. In fact, when your foot is on the ground, you could even say that a part of you is stopped (your foot)! This does not mean that you have to take long steps and go very high in the air (it is a waste of energy). The ideal is to have the most horizontal possible thrust and the shortest possible ground contact time.
What does a shorter TCS involve?
An athlete who has a shorter TCS generates more power. Remember the definition of power that you learned in your physics class. What was the equation?
Power = Force X Speed. This means that to reduce ground contact time, you have to be able to generate a good level of force quickly.
The studies
In this study, the researchers filmed more than 200 elite runners in the 15th kilometer of a half marathon. Shorter ground contact time was linked to better performance. A shorter contact time was also related to ground contact on the forefoot or midfoot.
Same thing in this Finnish study, in which the oxygen cost was measured for two different running speeds: 20km / h (points) and 23 km / h. We see in the table below that the shorter the ground contact time, the more efficient the athletes are.
In the next article, I will try to give you some tips that can help you decrease your ground contact time.
In the meantime, I invite you to share this article to let your friends know what TCS is!
Well done Daniel,
We are impatiently awaiting the rest.
Hello Daniel,
I really like your analyzes, and your step back from the “beliefs” that it is sometimes useful to demystify.
Precisely, since you often insist on not confusing cause and consequence (I agree with that, especially on the frequency of strides, the foot passing close to the buttock when the free leg returns to the before, etc…), don't you think that if runners who have a very short TCS are the fastest, it is precisely because they are the fastest: like the time they take to cover a distance of is shorter than for the average person, each phase of their stride will also be carried out faster, and will therefore be shorter, especially contact with the ground! ...
As for the economy of the race, if we continue the reasoning: this would therefore amount to saying that the fastest runners, who are those who have the shortest TCS, therefore, are the most economical ... but it is not because they have a shorter contact time with the ground that they are the most economical, it is rather that since they are the most economical, this naturally allows them to be the fastest, and necessarily, the fastest are those who have the lowest TCS, as specified in the previous paragraph…, right?…
Sincerely.
Christophe
Very good point Christophe. I certainly agree that the shorter TCS is not necessarily what gets you going faster and it's probably more of an effect of running faster than the cause.
Having said that, many runners, when they want to go faster, focus on the aerobic aspect of the run and neglect the muscle side. Sometimes some people are not “powerful” enough to run faster, and in this case exercises that help lower TCS can be helpful.
What do you think?
That this is not a parameter that we can "directly" improve during training, unlike the frequency of the stride for example.
TCS is just an effect of the power developed at a given time. The power being a product between speed and force of contraction, ca, ca, is worked (ppg, pps, ribs, etc ...)
So I would say, to go fast, we must not forget to work on power. With more power, you can go faster, and when you go faster, the TCS drops.
Very well said!