The best runners know that symmetry is important. If you apply force equally to the left and right sides of the body, you become more effective–and faster–runner. More importantly, you are less prone to injury.
Ground contact time balance (GCT) is an indicator that can help improve running symmetry.
In this article, learn about the balance of contact time with the ground and read our five tips for improving running symmetry.
What is the time of contact with the ground?
To understand the time of contact with the ground balance, starting from the time of contact with the ground, or abbreviated GCT. This is the amount of time your foot comes in contact with the ground while running. For most GCT runners, 200 to 300 milliseconds is normal. Elite distance runners are able to reduce the time of collision with the ground to 200 ms.
The part of contact with the ground of your gait is also known as the phase position. The rack phase begins with the initial kick of the foot, continues through the “load” and ends with the onset.
Why does the time of contact with the ground matter?
Running speed depends on the ability to quickly apply force through the ground. The faster you can apply force through the ground, the faster you will move forward.
Scientists have been studying the relationship between ground contact time and running speed for decades. But until recently, GCT was an inaccessible metric reserved for biomechanics in the laboratory.
Biological feedback and wearable technology
Wearable fitness equipment have made a revolution in fitness training and in the way we track our results. Trackers and accelerometers now offer accurate biological reviews in real time for runners everywhere and working.
The 2020 study was the first to examine the impact of biological feedback from wearable devices on operating biomechanics. The results were positive. Observing GCT biological feedback reduced vertical displacement (jumping) and running time and increased knee flexion – key factors for performance and injury prevention.
This brings us to the next evolution in feedback: gastrointestinal balance.
What is the ground contact time balance?
The ground contact time balance is a measure of how similar the ground contact time is on the left and right feet. The GCT balance is usually displayed as a percentage. A 50/50 split is the theoretical optimum and indicates an equal GCT for both legs. In fact, the balance of CGT is rarely 50/50. Anything between 49% and 51% is considered fairly symmetrical. However, if your GCT balance exceeds 49/51 (an imbalance of more than 2%), asymmetry can affect your performance and put you at risk for injury.
The ground contact time balance is a measure of how similar the ground contact time is on the left and right feet.
The GCT balance is usually displayed as a percentage. A 50/50 split is the theoretical optimum and indicates an equal GCT for both legs.
In fact, the balance of CGT is rarely 50/50. Anything between 49% and 51% is considered fairly symmetrical. However, if your GCT balance exceeds 49/51 (an imbalance of more than 2%), asymmetry can affect your performance and put you at risk for injury.
Why does the balance of contact time with the ground matter?
GCT balance matters because symmetry is important. Elite athletes show a high level of symmetry, and the fastest runners – the most symmetricaltrical. 
Asymmetry, on the other hand, is metabolically and biomechanically inefficient. This is because one side of your body works harder to compensate for the other.
For effective forward movement the most effective movement is from front to back (sagittal). When there is an imbalance, energy is expended by moving the body in the frontal plane (think of hip adduction) or the transverse plane (think of trunk rotation) to counteract the asymmetry.
For example, if one leg is weaker or less flexible, we tend to compensate for this with excessive hand swing or torso rotation.
What science says about the balance of CGT
The International Journal of Exercise Science last year published a study on the impact of CGT imbalances on a functioning economy. 
Notably, the study found that for every 1% CGT imbalance, the current economy declined by almost 4%.
To put this in perspective, for the GCT 49/51 balance (when one foot is in contact with the ground only 2% longer than the other), the energy required to operate at the same speed is 7.4% more.
For a 70-pound runner at 15 km / h this will increase oxygen consumption by ~ 4 ml.kg.min. This is a big part of your V̇O2 max.
It is not known exactly how much asymmetry causes injury.  However, it is anecdotal that any weakness on the one hand can cause additional strain on other muscles and joints, threatening the risk of subsequent injury. 
In short, balancing the time spent with each leg is important to prevent injuries and increase economy and efficiency.
Here are 5 tips to improve running symmetry and ground contact time balance
1. Determine the asymmetry
Use the GCT balance metric to find out which leg is slower. The foot with a higher percentage of GCT balance (> 50) spends more time in contact with the ground. You need to work on a slow leg.
Check the asymmetry by performing a stretch or exercise on each leg. This will help you identify differences in strength, balance and flexibility.
- How long can you stand on each leg with your eyes closed?
- Does your knee turn to one side during an accident?
- How far does each leg reach, lying on its back and pulling out the hamstrings?
2. Handle old injuries
In many cases, the asymmetry is related to past injuries. Pain or weakness in one damaged part of the body can lead to overcompensation in others. The asymmetry becomes a vicious circle of overcompensation that causes further weakness of the affected party due to underutilization.
Use GCT biological feedback to correct asymmetry in recovery from injury or retrain after adaptation to older injuries.
3. Strengthen muscles
To improve the symmetry of running and overcome the imbalance of contact time with the ground, focus on developing muscle strength and power.
One leg (one-sided) exercises both lunges and calf raises effectively develop your weaker leg and interfere with the dominant leg.
4. Optimize flexibility and rigidity
Inflexibility due to injury (e.g., from scar tissue) increases the likelihood of asymmetry. Include flexibility training in your schedule to overcome the tension associated with injuries.
Your range of motion should be specific to your business. You do not need the flexibility of a gymnast to run long distances. In fact, a certain degree of “tightness” can even improve performance. 
A recent study found that runners naturally adjust leg stiffness and ground contact time to optimize running savings.  A stiffer foot spring will return more energy after compression.
Include in your program plyometric exercises on one leg to increase the stiffness of the leg springs and reduce the time of contact with the ground.
5. The terrain changes
Running on flat terrain can worsen asymmetry. Try it pannuity over rough ground and a variety of gradients to enhance proprioception, balance, and strength.