The ultimate sprint training series. Part 4 - Understanding top speed running
In our last article in this series (see here) we discussed acceleration and the ways in which you can address getting off the mark faster. In this article we will introduce concepts around top speed running, what we know from the research evidence about how to run faster and look to highlight what areas can be addressed if you want to the highest top speed.
Firstly, lets look at what constitutes top speed and when we see this in sports. The popularity of GPS systems in professional field sports has given the broader sports community a greater appreciation of how far athletes run, but also how fast they sprint. Some of the numbers that field athletes are producing highlight that top speed sprinting is a significant factor in the physical requirements of elite professional field sports. Following the FIFA world cup last year there was significant interest in the top speed of players such as France’s Kylian Mbappe, who is suggested to have hit 38km/h in some of his blistering runs. To put this into context he is covering close to 11 meters every second. It is clear from his success that this is a huge weapon for the French striker.
So how do we get a faster top speed?
Well if we look at the current research into what makes people fast we must look into the biomechanics research that has contributed to this area. At top speed there is a very basic equation that explains how we get to top speed, this equation then allows us to determine how we may address getting there.
Velocity = Stride length (m) x Step Frequency (steps per second)
Using this equation we know that there is two key ways to run faster, take bigger steps or increase the speed at which you exchange your legs to take the next step. The balancing act is that in order to take large steps you need to push yourself off the ground with very high forces, this therefore places a limit on how short of a period that you can spend on the ground. Too little time and the force goes down (reducing how far you can push yourself) and too long on the ground you may have higher forces but your exchange speed is too slow and the number of steps you can take in a second reduces. To place this in context the top sprinting athletes in the world can take 4.5 to 5 steps per second and cover a distance of up to 1.3-1.4 times their height with each step. Bolt for instance during his world record run had a stride length of approximately 2.80 metres, at a step frequency of approximately 4.6 strides per second.
The work of researchers such as Peter Weyand and Ken Clark have looked into how this occurs and the answer that they come back to is that the best athletes in the world find a way to create a stiff platform and push their foot into the ground at extremely rapid velocities. The resulting forces (ground reaction forces) of top sprint athletes are as high as five times their body weight. These enormously high forces are put into the ground in as little as 0.08 seconds. So as you can see the balancing act is putting enormous force into the ground in a very short period of time.
So how are these athletes creating such high forces?
With such high force requirements at ground contact, it is easy to assume that getting extremely strong legs through exercises such as squatting, deadlifting, leg press will be required to produce such forces, but the answer is not so. Work as early as the 1970’s by Cavagna et al discusses that after the acceleration phase the forces required for top speed are heavily derived from elastic means.
Elastic energy is stored within our tissues (muscle, fascia, tendons, joint capsules, ligaments, connective tissue) when we place them on stretch at high velocities. An example of this is tapping your finger onto a desk. If you use your muscles to tap as hard as you can you will notice that you cannot generate much force or speed. However with no muscle action at all you can slam your finger into the desk at high speed and force by lifting the finger back using the other hand and letting it recoil on its own. What you have done is placed the elastic structures of the finger on stretch and then allowed the energy stored in those stretched tissues to impart the energy into the finger when you let it go. In a simple manner you have stretched the rubber band back and let it go. So when you move your legs forward and back you are essentially using your muscles to re-position the joints to allow the elastic structures to store elastic energy and then allowing them to release at the right times. In order to ensure that you don’t lose this energy it is important to create a stiff platform (foot, ankle,knee and hip) when you contact the ground so that it imparts the force into the ground and rebounds you back up into the air and forward as you run.
This creation of a stiff platform is generated in multiple ways. It is a product of understanding how to create tension in the right muscle-tendon units (essentially knowing how to coordinate the creation of stiffness through motor control), this process is driven by exposure to sprinting and technical running training, using strength training to establish how to create muscle tension and joint positioning for stiffness and through exposure to tasks that require high levels of joint stiffness such as repeated jumps. The added benefit of this training is that when the musculotendinous structures are exposed to this training they develop more structural stiffness (strength training and plyometrics increases the development of collagen cross links and muscle fibre properties to aid with passive stiffness qualities). So by using exposure to sprinting at high speeds and accessory training such as strength and plyometric training, we are asking the body to attain the ability to maintain greater stiffness of joint structures both through neuromuscular coordination and passive tissue changes.
The ability to have high step frequencies and fast accelerations of the limb into the ground are aided by a few key factors. The first is the ability to evoke reflex patterns. The most common pattern discussed is the crossed extensor reflex, this reflex essentially says that if you quickly bend up your hip, the opposite hip will push down as a reflex. There are a few ways to evoke this reflex but typically the initiation of a fast and aggressive arm swing down while running will cause the opposite leg to slam into the ground and bring on the reflex in the opposite leg. The added benefit is that reflexes are not only faster than muscle action alone, they require less energy.
The second way in which high frequencies with high limb velocities are created is through the use of the elastic stretch in muscle and passive structures mentioned above (the rubber band effect). If you allow energy to be stored in the structures through stretch, you will cause the stretch shorten cycle to impart increased limb speed onto the leg and foot as it hits the ground.
So with this in mind here are some take away tips to hit a higher top speed.
Use running mechanics and reflex patterns to accelerate the foot into the ground at a high speed, resulting in high ground reaction forces
Bounce off the ground with the stored elastic energy in your leg by creating a stiff landing platform
Use the bodies natural reflexes to exchange the limbs quickly and more efficiently
In the next article we will look at the type of training that you can do to learn how to create higher top speeds.