Does strength really translate over to speed?

Speed kills? How many times have we heard that?

Surf Instagram for long enough and I guarantee you will come across an extensive list of posts about how to improve an athletes 40 yard time. One particular discussion point that continues to come under the firing line is strength and its role in speed development. On one hand, we have athletes like Usain Bolt who demonstrate very average strength levels in comparison to his speed output. Then on the other hand there are the strong guys in the weight room who are also very fast, let's say Asafa Powell. 

So who's right? 

Well the reality is it’s a little more complicated than this.

What does the research say?  

If we take a look at a lot of the evidence when it comes to speed development, it will highlight that strength does in fact have a reasonable correlation to acceleration, to a certain extent…..

I wanted to cherry pick one particular study that makes a reasonable case from a theoretical perspective. This study below was by Wisloff (2004) highlighting the efficacy of maximal strength development on short acceleration performance. Notice the emphasis of acceleration and not top speed. 

What you will see in the graph above was there was a strong correlation between strength and speed for the first 10m of the sprint. Theoretically, this makes more sense. Ground contact times are going to be at their longest in the first few strides of acceleration. With longer ground contact times comes more time to produce force into the ground and a greater reliance on the muscle to produce concentric force instead of the tendons. This is highlighted in the image below by Derek Hansen.

However, what we start to notice is this correlation starts to weaken the further we sprint. If we zoom in on the 30m mark of the study below, what you will start to see is a smaller correlation in regards to acceleration performance. 

Although in this particular study the correlation is still pretty strong, it is significantly lower than over the first 10m of the sprint. What would have been interesting to see would be seeing the split times over the different segments of the 30m sprint. For example, what were the athletes split times between the 20-30m segment? and not the 30m as a whole. I could confidently suggest these splits would be much weaker despite the improved 30m times. These would only continue to weaken the further we sprint. From a theoretical standpoint, it may look something like this. 

So how does this differ for the field and court based athlete?

Well although speed is speed, one of the key differences between track sprinters and field and court based athletes is sport is predominantly played between 0-30m, Track sprinting is not. Quite often the track sprinter who rushes acceleration will decelerate earlier and therefore get run over the top in the remaining 30-40m in the 100m sprint. Ground contact times are also insanely fast at maximum velocity, as low as 0.8 seconds as seen on the earlier graph. There is simply not enough time to utilise maximum strength qualities to improve performance.

However this isn't as much of a concern for the field and court based athlete. The athlete who accelerates the fastest will get to the ball first, chase down an opponent, or break away from the contest. This is much more likely going to be influenced between that 0-30m range. 

But hang on a second? If it was as simple as getting stronger why are there so many athletes out there who are strong but slow? 

This is where it gets a little more complex and we need to consider a few variables. The first being relative strength. 

Relative strength:  Force = mass x acceleration

 Relative strength is how strong you are relative to your bodyweight, whereas absolute strength is how much total weight you can lift regardless of bodyweight. The athlete with the greater relative strength is going to require less effort to overcome inertia and get themselves moving. This is where the heavy but strong athlete hits their downfall. Having excessive body fat or particularly upper body hypertrophy (muscle) will require the athlete to exert more force to get the same outcome as the lighter athlete.

Picture we have two athletes with the same genetic make up and same sprinting technique. Let's put them through a full range of motion back squat and see the numbers we get.  

Athlete A weighs 75kg and can squat 160kg (2.13x BW)

Athlete B weight 100kg and can squat 160kg (1.60x BW)

Athlete A will win. 

As a rule of thumb I like my guys to be able to squat up to 2x bodyweight and as deep as their anatomy allows them. For most athletes this mark is likely going to be from 1.8-2.25x bodyweight. Now although relative strength is likely a better indicator for short acceleration, there are still plenty of athletes out there who are incredibly strong for their bodyweight who don’t accelerate super well. This is because we aren’t taking into account the variable of time. 

If we truly want to develop speed we need to ensure the following equation

Force x time / mass 

How much force can the athlete produce into the ground, within the allocated time (ground contact), all while being at the lowest mass possible for that particular athlete. 

I mentioned earlier ground contact times decrease very quickly with each step. By step 4 elite athletes are already down to 0.13 seconds. That is very fast. 

If we compare elite sprinters with simply strong athletes, max force doesn’t tend to differ a great deal, however what does significantly differ is the speed at which the sprinter can generate force. This is called Rate of force development or RFD. If we look at the image below by Ken Clark what you will see is a competitive sprinter and a field/court sport athlete. The sprinter was able to demonstrate more force in the first half of the ground contact compared to the athlete. The sprinter has a much higher rate of force development. The limiting factor is time. 

What about mechanics?

 It’s hard to analyse speed without taking some consideration into the role of mechanics. It’s all well and good to be able to be strong, however, if you are applying force in the wrong direction you are leaking energy. Let me give you an example. Below is an image from a Cam Josse presentation he did recently. On the top, we have 60m world record holder, Christian Coleman. On the bottom, we have an Indiana running back. What you will notice is the running back significantly overstriding compared to Coleman and applying a braking force on the body. This is essentially slowing him down. Now you can have all the strength in the world and have a top rig however this is going to significantly limit the amount of horizontal propulsion he is going to be able to exhibit.

So that's going to wrap up this blog. As you can tell acceleration and speed in particular is quite complex. It’s not as easy as simply getting stronger and acceleration will skyrocket. Although I highly recommend increasing your relative strength if you want to accelerate faster, you also need to factor in the other variables such as technique, body composition, rate of force development, stiffness and angular velocity if you want to sprint as fast as possible. 

I will likely break down how to improve all of these factors in future blogs, however, if you liked this blog make sure you give it a share and tag anyone who you feel will benefit from the read. 

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