Metric Monday: Why You Should Care About Your Ground Contact Time
Happy Metric Monday!
In this series, we take an in-depth look at a range of metrics which impact your running and one by one, detail their importance, what they mean, and how understanding and working to improve on each metric can help you in your running performance.
By understanding and working on these metrics for those crucial, performance-boosting marginal gains, you can improve on the key aspects of your form and technique and become a consistently better runner.
This week, we’re taking a good old look at your ground contact time.
Once an obscure metric, ground contact time is beginning to get the attention it deserves in the running world.
Ground contact time, or GCT, is one of the most underutilised performance metrics — and that’s despite the fact that it has been shown to have a direct impact on improving running results.
Your form and efficiency are particularly affected by your ground contact time, and research shows that runners who work on this particular metric actually produce better performances than those who don’t.
Here’s all you need to know about your ground contact time, and most importantly, how it can help you boost your running performance.
What is ground contact time?
Your ground contact time is the duration at which your foot is in contact with the ground — of course!
This is usually measured in milliseconds, between the first instance of your foot striking the ground to the moment it leaves the floor.
It’s determined by the position of your foot relative to the centre of mass at foot strike and the power you are able to generate from your legs.
Typically, your ground contact time will always decrease as your speed increases. The faster you move, the less need for your body to make longer contact with the ground.
You spend more time airborne due to your bounce, which therefore lessens the amount of time you spend with your feet in contact with the ground.
Why does it matter?
By understanding your ground contact time, you can work to make sure that you are airborne for longer which, in turn, will help you to preserve your energy for longer, be able to move faster, and shave seconds off of your overall best time.
Similar to how you track and improve on your cadence metric, you want to aim to have minimal contact with the ground in order to have a far more efficient form.
Not only does your ground contact time impact other measurable metrics key to your running performance, but it can also play a big part in keeping you injury-free.
Quite simply, the more time you spend with your feet in contact with the ground, the more chance you have of picking up an injury.
Think of it from a physical perspective — while you’re in the air, your joints (particularly your knees) are not experiencing any stress or pressure of maintaining body weight as you’re airborne and not in contact with the ground.
When you do make contact with the ground, however, your knees have to bend to adjust the weight and maintain momentum consistently for a successful run.
Therefore, you want to be aiming to stay airborne for longer and reduce the amount of time you spend in contact with the ground, as it reduces the duration of time spent increasing the risk of injury.
By taking into consideration the impact that your ground contact time has on your performance, you can alleviate the risk of injuries like ‘runner’s knee’, deeper knee fluxion or iliotibial band syndrome (ITB).
What does the science say?
Research has shown that by working on improving your ground contact time, you in turn positively impact other key metrics in your running.
For example, your ground contact time also works to influence your cadence — the number of steps taken per minute — and you bounce — your vertical movement during a run (we previously wrote a whole Metric Monday blog on your bounce, which you can read here).
Because your ground contact time fundamentally measures the duration of time your feet spend in contact with the ground, it, in turn, has an impact on how many steps you take per minute and how high your vertical oscillation is too.
In fact, according to a variety of studies of runner’s ground contact time, runners who have lower GCT are on average able to use less energy than those with higher numbers.
What’s more, those runners with a lower GCT have the potential to run considerably faster too, simply because they’re spending less time on the ground and minimalising the halting of their forward propelling momentum.
This is known as breaking, and it has an influence on a variety of different metrics and your overall efficiency. It occurs when your foot is in contact with the ground for too long and/or your footstrike (most typically heelstrike) causes a braking motion. Obviously then, for a more economic running style, you should aim to keep breaking to a minimum.
Not only is breaking inefficient by disrupting your stride and influencing your cadence, ground contact time, and more, but it can also add to the risk of injury too. That’s because it places a considerably bigger strain on your feet and knees.
Can I improve my ground contact time?
Like many important running metrics, your ground contact time will depend on your own performance. It’s dependant on your physique, ability, capabilities, and other personal variables, meaning that it makes little sense to compare to how other runners are performing on their GCT.
However, you can still work to train your ground contact time and reap rewards that will see you run faster and for longer.
It’s typically believed that the target that elite runners and athletes typically aim for is to have a ground contact time of around 200ms.
That said, a score below 300 is ideal for most runners, with a metric around 260 typically considered excellent for the average runner.
Aiming for an improved ground contact time can boost your running performance no end, improving metrics like your cadence, bounce, speed, and energy used, which all work to make your running more efficient, economical and robust.
In particular, one way that you can work to improve on your GCT is through power training your legs. With more power in your legs, you’ll be able to generate more force which you can apply when making contact with the ground.
Power training your legs will equip you with more strength where it matters, allowing you to push off the ground and stay elevated for longer.
You should also be aiming to achieve a stiffness in your leg at the moment of footstrike. This stiffness will give your legs more ability to recycle energy from the ground and generate more power in pushing off.
Again, this can be improved by power training your legs — with jumping drills and weight lifting recommended to help maximise the strength and stiffness in your legs.
However you choose to focus on your GCT, by measuring the metric as you run, you can be safe in the knowledge that you’re on your way to becoming a better, more complete runner.