Introduction: Force-Velocity Profiling

The saying ‘you can’t train speed’ is a common cliché bandied about by sports commentators when describing the athleticism of the likes of a Killian Mbappé, Jack McCaffrey or a Shelly Ann Fraser Pryce. While there is a significant genetic contribution to the development of elite level speed, there are also numerous modifiable physical qualities that can greatly enhance an athlete’s acceleration and top end velocity. But what separates the athlete who spends hours upon hours under the barbell trying to develop their maximal strength and power with the flyer who is nowhere to be seen near the top of the early season strength testing leaderboards.

We recently had JB Morin over from France to enhance our rehabilitation protocols, to reduce injury and improve sprinting performance. We will be using these protocols in our physiotherapy clinics in Rathfarnham - Knocklyon, Sandyford and Greystones to improve our return to play protocols.

In this article, we’ll explain how those qualities which are currently limiting an athlete’s sprint speed performance and potentially contributing to an increased injury risk can be assessed. More importantly, we’ll address how this assessment informs an athlete’s individualized rehab programming and return to high performance.

Fundamentals of Speed:

When running, we exert a force opposite the direction of motion. By Newtons 3rd Law, the ground then exerts a force on us equal and opposite to our force on the ground, allowing forward motion.

In simple terms to achieve high sprint speeds we need to be able to produce high amounts of force in very short spaces of time in the right directions.

Horizontal v Vertical Force:

For the purposes of the Force-Velocity Profile, the application of force when sprinting is broken down into horizontal force (pushing backwards with a more forward trunk orientation) and vertical force (pushing downwards with a more upright trunk orientation). When we are accelerating, having a higher ratio of our total force production in the horizontal direction tends to be favourable towards generating forward momentum. As we begin to pick up speed, our body will gradually rise as we spend more time in the air, our ratio of vertical force will increase. This is why when we accelerate, you may hear your coach use cues such as push the ground back or attack back, where’s the cues may be more vertically focused when sprinting upright, such as attack down and back or imagine you’re squashing an orange under your body.

Cues and constraints can be helpful in coaching athletes to produce this horizontal force. A sled is a useful tool as it provided a horizontal resistance from behind. For us to move the sled, we are forced to produce an increased degree of horizontal force. When pulling a sled or pushing a prowler, we also tend to have a more forward oriented posture which is more conducive towards being able to push the ground back and behind us. A natural tendency of athletes who tend to have a poor ratio of horizontal force and an excessive degree of vertical force when accelerating is to produce a high degree of vertical force to avoid falling over. Especially taller athletes tend to struggle with this ability. Our individual limb lengths and body shape influences our ability to produce horizontal forceas taller athletes are naturally more prone to being upright. These athletes especially require good ankle mobility and eccentric quadriceps strength to be able to achieve the necessary forward orientated starting position needed to launch themselves explosively out of the blocks.

Testing Protocol:

In the clinic, we use a 30m sprint test to form an athletes’ Force-Velocity Profile. This is undertaken using the MySprint App which has been scientifically proven to have an accuracy comparable to lab testing. The 30m sprint is broken up into 5m segments, with slight deviations of this distance taking the camera angle into account. Once the sprint has been completed, a profile is generated with key pieces of information used to inform programming.

How this informs training:

Your Physiotherapist can then compare the various metrics versus standards set by reference standards for team sport athletes. Examples of these metrics include Ratio of Force (RF): The ratio of force produced in a horizontal direction. An excessive ratio of vertical force as compared to horizontal force for example tends to result in an athlete rising into an upright posture too quickly without gaining significant forward displacement.

Other important metrics include Theoretical maximum force production (F0) which is related to max horizontal strength and Theoretical maximum velocity (V0) which is the theoretical maximum speed an athlete can achieve given the current level of training. If an athlete appears to be getting closer to reference standards of maximal force production while they lag in maximum velocity, they may benefit from training with lighter sled loads and making sure to hit >95% of their top speed on a regular basis. Athletes who have a higher V0 score and a lower F0 tend to benefit more from heavier sled loads and may also benefit from strength work focusing on muscle groups which contribute to horizontal projection such as the glutes, hamstrings, and calves.

Conclusion:

In summary, once the force-velocity profile has been completed we will have a good idea of where our main training priorities lie. How many potential speed gains are you leaving on the table and how fast could you move with a more targeted training or rehab programme? As the esteemed sprint science researcher and coach JB Morin described at a recent workshop in SPARC, training is like squeezing a tube of toothpaste. This relates to training as when we begin strength-based work as part of our athletic development programme as a youth athlete, any form of strength training may lead to gains in speed, like when we first squeeze the toothpaste tube. However, the more training we undertake, the more specific and individualised our training programme needs to become to continue to make speed gains, like how it becomes increasingly difficult to squeeze toothpaste from the tube the longer we’ve been working our way through it!

If you are interested in learning more on how force velocity profiling could help you or your athletes, drop us a message via whatsapp using the gold button in the bottom corner of your screen!