Introduction
If you want to improve your acceleration it is advisable to film yourself accelerating, and then review the footage to spot shortcomings in your form. However, to do so effectively, understanding the mechanics behind an efficient acceleration is crucial. That is what we will discuss in this article.
Acceleration is defined as the change in your velocity over time. In other words, acceleration is how fast you can increase your speed. If you reach your top speed very quickly, it generally means you have good acceleration (although it could also just mean that you have a relatively low top speed).
Acceleration is the quality that is usually most desirable when it comes to most field sports, since most explosive movements and sprints occurs over a small distance. So, how can we improve our acceleration abilities?
Locomotion And Moving Forward
Horizontal Force
To answer this, we should think about the basic physics of locomotion. If we want to move in a horizontal direction, then we must apply force in a horizontal direction.
For instance, if we apply force in a purely vertical direction – also known as a vertical jump – then we of course will not move forward. Conversely, if we want to move forward, we must apply force in a horizontal direction.
Specifically, we must apply force in a horizontal force behind us since we want to move forward. Therefore, the faster you apply large amounts of force behind you, the greater your acceleration will be.
How Can We Produce More Horizontal Force?
So, we may wonder how we can improve our ability to produce more horizontal force – in other words, how to improve our acceleration. The answer to this question has two components
- Train ourselves to be able to produce more total force
- Train ourselves to direct this force in a more efficient way (i.e – in the horizontal plane)
The first component is typically a lengthier process that, generally speaking, involves becoming stronger through traditional gym-based exercises and then training to produce high levels of force in a short period of time (in other words, to become more powerful). This aspect of training will be discussed at another time.
The remainder of this article will therefore focus on component 2 – training ourselves to have more efficient acceleration mechanics.
This article will be somewhat technical, but it is important to understand the core concepts behind acceleration mechanics because then you will be able spot errors and areas for improvement when reviewing footage of your own accelerations.
Conversely, not understanding these concepts will make that difficult or even mislead you. For example, you may think you need to ‘stay lower’ when actually the opposite is true.
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Acceleration Mechanics
Leaning Forward
The best way to apply force in a horizontal direction behind us is when we are at a slight lean forward. We may intuitively realize this is the case from experience. However, understanding why this is the case is important.
The reason why a slight lean forward is desirable is because it allows us to efficiently push the ground in a horizontal direction.
Notice how all athletes are leaning forward at the start of the race.
All this talk of ‘applying force in a horizontal direction’ may seem abstract and confusing but really the concept is quite simple.
Consider a situation where you want to jump as high as possible upwards. In this case, you would push your feet right down into the group almost in a straight line before exploding up into the air. In this case, you would be applying a lot of force in the vertical direction.
Now imagine that your car is stuck, and you (and likely a bunch of others) are pushing the car from behind. In this case, since you want to move the car forward, your feet would not be going straight into the ground. Rather, you would likely be up higher on your midfoot/forefoot, your heel off the ground and your shins at a steeper angle (much like the athletes in the above picture). Indeed, this pose is very conducive to generating the horizontal force required to move the car forward.
Pushing a car forward. Note the forward lean and the shins at an angle.
Shin Angles
The point I mentioned about your shins being at a steeper angle is a very important one. This is because the angle of your shins reveals the proportion of force going in the vertical vs the horizontal direction.
Let’s recall the example of the vertical jump. Here, your shins will be perpendicular with the ground (90 degrees). Whereas, in the car example and with the sprinters above, the shin angles are much more acute (closer to 45-50 degrees).
In fact, the steeper the shin angle, the more force is being applied horizontally. This is why shin angles are so important, as they act as a clear indicator of how force is being applied.
Shin angles. For those more technically minded, you can see how the force vector revealed by the shin angle can be decomposed into its vertical and horizontal components. Now it is clear that the steeper the shin angle, the greater the horizontal force component is.
Now it’s clear why we want to have a slight lean forward during our accelerations: this will allow us to achieve better (smaller) shin angles, allowing us to put more force in the horizontal direction and to therefore increase our acceleration.
Doing this would be very difficult from a standing position, hence why sprinters begin on the ground with a 4-point stance, as this will allow them to achieve an optimal acceleration position immediately after exiting the blocks.
This also explains the famous acceleration cue “Stay low”. The idea behind this cue is that by telling ourselves to stay low during acceleration, we will lean forward and avoid getting tall. This then allows us to push behind us, achieve good shin angles and consequently have a good acceleration.
Knowing this you may think
“Alright, so I just have to get very low by leaning forward a lot and then I will be able to achieve good shin angles and accelerate well”
Well, it’s not so simple. Actually, this thought brings up what I believe to be the fundamental ‘issue’ of acceleration.
It's Not Just About Staying Low
Overstriding
It’s obvious to most people what will happen if you try and stay ‘too low’. There will come a point where attempting to run with such a drastic forward lean will just result in you falling forward onto your face.
However, it is rarely the case that someone’s forward lean is so exaggerated that they actually fall over (although stumbling out of the blocks is sometimes seen, even by the GOAT).
What tends to happen is instead much more insidious.
Usain Bolt staying too low out of the blocks and subsequently stumbling early on in various races
When you lean too far forward in an attempt to ‘get low’, your body will sense that you are going to fall over and so you will naturally take your next step far in front of you to prevent this. This is known as overstriding.
Overstriding is detrimental when it comes to your acceleration mechanics and is a sign that you are leaning too far forward. The reason why overstriding is detrimental to an efficient acceleration is because you are landing in front of your centre of mass (COM).
For the purposes of this article, you can think of your COM during acceleration as your hips. When you place your foot in front of your COM/your hips, it makes it very difficult to push backwards with that foot.
For example, try standing up, putting one foot in front of you and then trying to push the ground backwards to move yourself forward. Now do the same but instead put one foot behind you and try to push the ground backwards to move yourself forward.
You should of course find that the latter is much easier. Likewise, when you overstride, you cannot effectively push the ground with the foot that has just landed since it is in front of your COM. Rather, you must wait for your body to move forward (due to the momentum you have already built up in your acceleration) until your planted foot is under or behind your COM after which you can effectively push.
This obviously wastes time since you must wait for your body to come forward before you can push. This may sound a bit confusing so let’s watch a good and a bad example to demonstrate. A while back I made an Instagram post showing the progress over time of the current Olympic champion, Marcell Jacobs.
Marcell Jacobs' Start Progression
This is a great example of overstriding. Back in 2019, it looks like Jacobs was too focused on ‘staying low’ and having an excessive forward lean. In the clip above, you can see that by his 4th step he has to stick his foot out in front of his hips as a natural response to his body falling over, thus overstriding.
Also, look at Jacobs shin angle when he overstrides on his 4th step – it’s almost completely vertical. In other words, that foot is not able to generate any horizontal force when it lands. Rather, Jacobs must wait for his body to move forward before he can effectively push with that foot. Now compare that to Jacobs’ acceleration in 2021.
With less of an emphasis on leaning forward and ‘staying low’, Jacobs can ensure that every step strikes backwards either behind or under his COM. This results in great shin angles. Nowadays Jacobs, being the current 100m Olympic champion and 60m indoor world champion, has one of the best accelerations in the world.
Staying Low and Overstriding - A Fine Balance
This brings us to what I previously called the fundamental ‘issue’ of acceleration: the fine balance between staying low and overstriding.
As I explained earlier, you want to adopt a slight forward lean (thereby ‘staying low’) so that you can achieve better shin angles. In other words, you can allow your feet to contact the ground in such a way that will maximize the amount of force applied in the horizontal direction (remember the car push example).
However, you also don’t want to stay too low as this will result in you inevitably overstriding, thus slowing down your acceleration. Hence, it’s all about finding that midpoint: A point where you lean forward enough to generate high amounts of horizontal force, but not leaning too far forward as that will cause you to overstride.
In my opinion, it seems that the ‘stay low’ side of the scale is overemphasized by beginners trying to improve their acceleration. This is probably because ‘remember to stay low’ is one of the first things you see or hear when researching how to improve your acceleration.
Elite sprinters are able to stay very low whilst also not overstriding. People then watch these sprinters and naturally try to mimic them, which leads to them getting much lower than their body can comfortably handle, resulting in overstriding.
Elite sprinter Christian Coleman is able to get very low and achieve great shin angles without overstriding. He currently holds the 60m world record and is considered to be one of the greatest accelerators of all time.
Also, noticing that one is overstriding can often be difficult as the smallest of margins can make a big difference. However, hopefully now you – the reader – after understanding these concepts will be able to accurately review your own accelerations.
If your shin angles are very vertical and your body is quite tall, then you probably are not staying low enough.
On the other hand, if you find that early on in your acceleration you are putting your feet in front of your hips and not striking backwards under or behind your hips, then you are probably overstriding. This is perhaps a symptom of an excessive forward lean.
Conclusion
There are of course many other aspects of acceleration such as triple extension, arm action, heel recovery, block settings (if you happen to be a track and field athlete) and so on.
However, what they all ultimately come back to is quickly and efficiently applying force in the backwards horizontal direction as discussed here.
These finer aspects of acceleration will be covered at a different time. Also, it should be mentioned that teaching your body to efficiently accelerate is by and large not a conscious process. Just like riding a bike or playing a piano, acceleration happens too fast for you to consciously control every aspect of your movement. Therefore, you must teach your body to intuitively and naturally adopt efficient acceleration mechanics. This is done through various exercises and drills. However, reviewing footage of your own accelerations and spotting the errors can help you detect your weaknesses and thus direct your training. Hopefully, after finishing this article you are in a better place to do just that.
Follow up: I’ve written an article that goes over what I believe to be by far the best exercise to improve your horizontal force production capabilities and hence your acceleration. You can find it here.
