Running &

Ground contact time.

During running, ground contact is of great influence. Ground contact leads to a landing moment as well as a new push off during running. If you want to run faster or more efficiently, it is wise to look at your running technique/style. This can be done through image analysis, but also with the help of an expert or a (sports) physical therapist. Each landing catches two to three times your body weight. If you have an incorrect running technique, this can have consequences for your body, increasing the risk of injuries. In this blog we will take a closer look at the running principle: ground contact time. But also what effect this has on your running performance. As you may know, your performance during running depends on several factors. Often these include Vo2max (maximum oxygen uptake), lactate tolerance (acidification) but also, for example, external factors such as weather conditions and footwear. We too feel that these few examples are certainly relevant when it comes to running performance, but would like to add another important pillar in this blog; ground contact.

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What is ground contact time?

Ground contact time means the time between the landing and push-off moment where your feet make contact with the ground. Looking at the top athletes, the ground contact time is as short as possible. This is measured in milliseconds, a top athlete has a ground contact time of less than 300msec. Depending on what type of runner you are, the shorter your ground contact time will be. The moment of landing and lifting the foot again also plays into the speeds top athletes can handle (running pace). By lifting the feet again quickly, this in turn affects the next movement (the push-off followed after landing), so a runner does not create a braking movement while running. Through data (measured with running watches, for example) you can find out what your ground contact time is (regardless of what type of training). It is plausible that an experienced short-distance runner (maximum 800m) has a shorter ground contact time than an experienced marathon runner (42,195km) because they have a totally different energy distribution but also use a totally different energy system for this. Ground contact time plays a role in every runner and has a different impact in every runner. 

Improve running performance

If you are an avid runner yourself, you probably know that most runners are fairly performance-oriented. Examples of this are extending distance (kilometers covered per run/per x period) or the time it takes to cover a certain distance (pace). Ground contact time (GCT)=time in which the foot has contact with the surface) appears to be an important parameter when it comes to performance during running. Besides the fact that optimizing ground contact time can contribute to a higher running speed, running efficiency also increases. Da means that it takes our body less work to perform the activity than when we have a greater ground contact time.

An example is simply accelerating from 8km/h to 10km/h while running. The moment you initiate such an acceleration you may notice that the time in which you have contact with the ground decreases but your stride length will increase. We know that even though different people can run the same speed, their ground contact time can differ between them, but also that the fastest runners generally have the least long GCT. This implies that training for a reduced GCT might have a positive effect on your performance while running. The idea behind this is that you actually only advance during the gliding moments and thus long ground contact moments reduce speed. Experienced runners have been found to have a GCT of less than 300 milliseconds per stride. 

How do you reduce your ground contact time?

Fortunately, we can say something about this based on studies! There seem to be three factors that mainly influence your GCT, namely; the ability to generate a lot of force on the ground at high speed, stiffness in the leg during the footstrike and biomechanical aspects such as foot position and body center of gravity during the footstrike. A higher speed and being able to generate a lot of force helps create (forward) speed in our running pattern. In addition, stiffness in the leg at the footstrike provides the ability to store and release more energy at the push-off. Furthermore, we know that foot position and body center of gravity affect the efficiency of our running pattern. If we place our foot too far forward (too long stride length) or if we place our body's center of gravity too far forward/backward, we are like a brake in our movement pattern. Because we thereby slow ourselves down, the GCT will always increase but also the amount of energy we need in walking.

The torso has a big influence on your ground contact time. Running with an upright running posture (chest forward, shoulders back) can affect your running technique. Your hip and gluteal muscles greatly affect your forefoot landing. The goal of good running technique, is to place the feet below the body's center of gravity (time-efficient). When you place your feet in front of the body's center of gravity, your entire body must first cross this point before a new push-off moment can occur.

The gluteal and hip muscles catch a lot during running. For this reason, we recommend strength training that will make these muscles powerful enough to cushion the running landing, time after time. Some example exercises for the buttock and hip muscles are: lunges, squats, bulgarian split squats, etc. Strength training is one way to prevent running injuries. Some exercises that can help you do this and also help you have a short ground contact time are listed below.

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Bil and leg muscle exercises for runners

What can you do to improve running performance and how best to influence it?

Ultimately, improving performance often comes down to training and quality of movement, so here too. Studies have shown that heavy strength training and plyometric exercises lend themselves very well to increasing leg stiffness during running. To cite an example, in a study where multiple heavy sets of squats were performed 4x a week, substantial positive results were measured on running efficiency and distance-time ratio. So this gives you several options. You can choose to hit the gym now and start working hard with strength training and plyometric exercises such as box jumps etc. Another option is to add plyometric exercises to your running training or finish your training regularly with a number of big sprints to increase strength while running. 

 

Exercises for plyometrics that you can practice in the gym/home

Another possibility is to improve the quality and efficiency of movement by paying attention to foot placement. Indeed, a Japanese study during a half marathon showed that there is a strong correspondence between foot placement and ground contact time. Here it was found that the midfoot strike is more effective and greatly reduces GCT compared to the heelstrike landing and thus can improve running times.  

 

Biomechanics during running
At the moment of landing, your body absorbs the energy of that force. Your knees, for example, bend (flex) to absorb the impact of the landing and to slow the body's center of gravity'. Ground contact time has a lot to do with biomechanics of the body. For example, in some runners, you see a certain running pattern that limits good performance because energy is absorbed. This can be due to a trendelenburg pattern (hip sag), an unstable upper body (swinging stance) or by the knees turning inward while landing (kneeing-in phenomenon). Now, the aforementioned factors should not so much be labeled as "wrong," but can potentially lead to injury or increase the likelihood. 

The perfect running technique
There is no such thing as a perfect running technique. Every runner runs in their own way. However, there are factors that influence your running performance and minimize the chance of injury. Now there is also no scientific evidence describing that your own running technique can lead to injury. Now, some of your running technique is innate, but of course you can influence it through running training, feedback (e.g., filming) and being conscious (explicit) about it. Good running technique can eventually lead to complaints, depending on numerous factors, but terrible running technique can also lead to no complaints. If you are used to always running with a kneeing in pattern (turning the knees inward while landing), but this never leads to complaints, why would you want to adjust it anyway? Provided someone does have complaints, it makes sense to "tinker" a bit with someone's running pattern, but if you have no complaints and are running top performance, why tinker? 

Want to get faster or are you interested in a movement analysis? Then make an appointment at www.fysiofitaal.nl

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Fleur Prins

Movement educator, physical therapist i.o.

I currently already work as an exercise instructor and have experience within the fitness industry as a fitness instructor (prior education: sports and exercise). Besides my education, I work a few evenings at Fysio Fitaal to further develop myself. Furthermore, I am enthusiastic about everything concerning sports, with my own favorite; running!

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