RTP Interview #2 Rich Clarke

At RTP, we are delighted to have Rich Clarke (@RICH_AgilityLab) with us for this interview. Rich is a Senior Lecturer in Strength and Conditioning at Birmingham City University. He is also completing his PhD investigating deceleration during change of direction tasks and works with athletes of various performance levels.

RTP: In our first website article we talk about change of direction (COD), detailing the factors that determine it, the importance of accurate measurement and the fundamental role of deceleration as a key moment.

In the context of team sports, could you give us an overview on how you view COD, the performance and injury trade off and the role of deceleration?

Rich: Firstly, a big thank you to Jorge for asking me to share some thoughts, I spend the majority of my day thinking about the area of COD and Agility so it’s great to share in more detail!

One of the things which helps coaches think about different types of movements is Ian Jeffreys Gamespeed model. He categorises movements into Actualisation movements (Sprinting or accelerating), Initiation movements (starting a movement and changing direction) and Transitional movements (waiting to react). Typically, Initiation movements are the action of changing direction, and this is where the challenging technical information is.

I tend to break down COD performance into a few different key principles, as to be quite honest, I like simplicity. To be clear, these are in the context of a COD which is followed by a maximal acceleration. These are neither perfect, or finished but it is currently how I think.

Key Principles:

  1. Get to the sagittal plane, if you are going to accelerate, this is always your goal
  2. Effectively adjust your feet and your centre of mass so you can push in the right direction
  3. Maximise your application of force and ensure that your trunk is working with you, not against you

There are some additional things to add here, which are more suited to when the scenario becomes a little more complex. These are:

  1. If you are moving at speed – match your movement speed to optimise the time available for the COD. Moving too fast means less ground contact time and more centre of mass momentum to control.
  2. If you are changing direction, but not going into an acceleration – then you likely need to return to face the original direction promptly, so don’t commit your torso and commit your hips as little as possible.

Touching on deceleration and point 4: Speed gives you less time, makes you less manoeuvrable and increases your injury risk if a COD scenario comes along. If the COD task which emerges requires you to be running at a slower speed (because of needed GCT or the time you need to decide etc) then deceleration needs to occur. If deceleration is needed but it doesn’t occur, you are more likely to be unsuccessful or get injured. So that puts it very high on our importance list! So far, this has been forgotten by many. We haven’t looked at it in the research effectively or got any clear practical resources on it. There is therefore, lots to be done and this is something that I am hoping to achieve through my PhD and share through Athlete Agility Lab.

Moving on to the complicated situation of injury risk…. This is a complete minefield due to it generally being accepted that there is a performance and injury trade off in COD movements. But again, doing what I usually do and making things simple, here are a few ways I look at it.

Firstly an important starting point: In order for an injury to occur there needs to be 2 risk factors.

  1. An ‘at risk’ position. More formally for ACL, a knee abduction moment (KAM).  
  2. Enough load to rupture the tissues.

These in my opinion are strongly linked by speed.

Increased speed means:

  1. Less time to prepare your body position.  
  2. More GRF at the plant step
  3. More COM momentum

If deceleration is required, it also results in a braking step that needs to be further in front of the body with more heel contact.

My opinion is we have lots of information on the mechanics and we now need to move on to different questions. In fact, a lot of the ‘at-risk’ mechanics we have concluded in the past, we can’t do a huge amount about in my opinion. This is not me saying they don’t matter, or we cant change them at all, but there are lots or things that point towards some of them being difficult to change, or even, incorrect to change.

For example:

  1. Lateral foot placement –The foot placement helps us produce lateral GRF to complete large angle cuts.
  2. Extended knee positions – If we are moving fast and need to brake, we will generally get more braking GRF if our foot is further in front of us, just like the above. A foot further in front, will usually need a more extended knee.
  3. Lateral trunk flexion – This one for me is key, we don’t need this for performance, but it is a consequence of moving quickly and having high levels of momentum. Improving deceleration and speed control potentially goes a long way to improving this, so this is a big one to look out for.
  4. Knee valgus – Another important one we can manipulate. There are still some questions outstanding, but generally I recommend improved neuro-muscular control and increased strength levels to deal with an minimise these positions.

Moving away from a technical perspective, the physical predictors or surrogate measures again come down to some simple things. The first; strength is a performance enhancer. Who knew right? To be COD specific, have a general focus on eccentric and isometric strength, which can convert to stiffness and reactive strength. But it varies a little with the type of COD, for example high speed cutting vs a 180 turn. After that, linear speed is your biggest predictor depending how we are measuring ‘COD performance’. While I am a huge COD and agility geek, there is no getting away from linear speed is king in most sports.

My current bias is that the speed control and deceleration ability are our next big steps. This reduces load, gives more time to manipulate BOS, allows improved control of COM (less momentum) and also gives more movement options.

RTP: Within sporting contexts, there are actions which suggest a high risk for our athlete. How can we evaluate the pattern of movement of these types of actions within specific environment? Should we prepare our athlete for this type of demand?  

Rich: As I am sure everyone has worked out, this is really difficult to do as the situation that an athlete is placed in is constantly changing, and arguably no two are the same. This makes evaluation difficult, or at least objective evaluation difficult.

The main thing I think we need to do here is embrace that it isn’t and likely never will be an exact science. Between all the interacting constraints and the added complexity of perception and cognition, we just can’t accurately evaluate what is going on and why.

The best I think we can do is look for trends. Don’t over analyse one particular case. It’s easy for people to do that when there has been an injury. Anyone can look back at a video and decide that ‘we should have changed this’ ‘this is why it happened’ but that is a fool’s-errand if you are only reviewing one video. Where you need to focus is what their habits are. When you watch people play, how to they tend to complete tasks? Do they like to maintain their speed and avoid deceleration? Do they link to limit their approach speed and make a very sudden and sharp cut to either direction? Do they like to rely on deceiving defenders? Do they use a wide foot plant in all scenarios? Do they seem to lose control of their trunk and have lots of lateral sway?

There are lots of things to think about and consider, but if you watch people compete, or analyse what they do holistically through some agility games where you manipulate the constraints, you’ll start to understand how the athlete approaches things and what they are and are not able to do. Once you think you have an idea of how they athlete completes things, you then have the decision of what do you change (if anything)? Do you do this through regular explicit coaching or through exposing them to tasks which are best completed in a different way? Regardless of what you decide, you need to concurrently prepare them to deal with the demands of how they complete it through good quality strength development.

RTP: When measuring CoD,in the literaturewe find many papers on evaluating the CoD Deficit which enables us to find out the player’s capacity for changing direction in relation to their linear speed. But you go beyond that and talk about Deceleration deficit. What is it, what information does it provide and how can we use it?

Rich: Deceleration deficit is, as the name suggests, essentially the concept of the COD deficit applied to deceleration. In both the COD deficit and the Deceleration deficit, you take two tasks over the same distance, one with a COD (for COD deficit) and one with a deceleration (for the Deceleration deficit).

Most commonly: COD deficit = 505 time minus Linear 10m sprint

My current work with the Deceleration deficit uses the equation: Time to get to the turn line in a 505 test minus a linear 15m sprint.

The reason this isolates the deceleration ability is in a traditional 505 test, you sprint for 10m, then have a 5m deceleration phase before stopping to re-accelerate into the new direction. So you essentially cover 15m as fast as possible when you stop on the 15m line. Minus the time it would have taken an athlete to do this without the stopping component (15m linear sprint) and you have the time that athlete needs to come to a stop. I consider the Deceleration defict relatively time efficient and user friendly, but there are a few different logistical things to consider, so feel free to reach out with questions or ask for help.

This principle can be applied over any distance and for the COD deficit, any angle. But there are less options for deceleration deficit as you need to use a task which requires a full stop. Hence why the 505 test is perfect. The 505 test also allows you to investigate each side independently. This in my opinion is important as you do see athletes with asymmetries that really struggle during the braking phase.

I have a paper on this under review at the moment, but I also recorded a video explaining it on the UKSCA website. If you aren’t a member, you can get 14 days access for free to watch it (I think), but I’d really encourage you to become a member. It’s great value for money and lots happening to generally support the S&C profession.

I am hoping this really gives us a step forward to measure how effective someone is at decelerating. Being able to measure it will also allow the understanding of this performance quality to develop more at time goes on, as there is a HUGE gap in our understanding at present.

RTP: There is lots of discussion of pre-planned and reactive drills and assessments, do we know how the environment in which actions take place influence these risk factors? What variables help us to understand the context in which the athlete performs?

Rich: Huge can of worms here! If anyone hasn’t, I recommend a read of ‘The Dynamics of Skill Acquisition by Keith Davids and the Constraints-Led Approach by Ian Renshaw et al. Both useful resources for understanding the interaction of constraints and how we need to view COD and agility performance. In short, we have a range of constraints that interact and lead to our movement outcome. Those that the individual bring themselves (strength, skill anthropometrics etc), then those in the environment (e.g defenders, space etc) and the task (the athletes goal/intention).

One of the first steps as a practitioner is to analyse how the athlete is challenged in competition. What is their task? How does the environment constrain their methods of completion? I think we need to understand these in much more detail. For example, Are they asked to cut to large angles at high speed? Or are they challenged to deceive defenders frequently? Is their scenario most commonly defensive or offensive? These answers are then evaluated in conjunction to the earlier question about movement trends and habits. My general recommendation is look at what speeds people commonly move at, how much time and space they are afforded, whether they are defensive or offensive and if there is a deception requirement. These are certainly a good start. Then we can identify what the key performance outcomes are and when the highest risk scenarios occur. All pieces of a puzzle to gradually put together.

RTP: In the case of change of direction, how can we apply constraints in our training process and incorporate them into agility?

Rich: As mentioned earlier, constraints are very important to understand. I gave some examples earlier of different types of constraints and the fact there is an interaction between the organism, the task and the environment. Generally, a constraint is something that sets a boundary or a limitation to how we are able to solve problems. So the pitch size is a constraint, as it shows where we can’t run, the surface is a constraint as playing a game on ice results in different movements to grass and strength levels of the athlete are a constraint as we don’t tend to use positions and movements we don’t have the capacity to support.

The main area where we can influence things and use constraints in training is by manipulating the environment the athlete is in. For example, if we give an athlete an agility task, we can adapt the environment to constrain the athlete options and encourage a different movement. Typically this is a better way to go about things as you aren’t explicitly instructing the athlete what to do or how to do it, you are just changing the information which is available and letting them make their own decisions suited to what their capabilities are. The individual constraints are hard to change acutely, we need long term interventions for that. But some acute things such as fatigue could be used. Finally, I don’t recommend changing the task too much. The task is one of the most important things for specificity. The task tends to dictate an athletes attention, which will obviously change what information they pick up and how they eventually solve the problem.

A quick example:

If an athlete always likes to maintain their speed and avoid deceleration when trying to complete a task. We can construct an environment which allows them to get up to speed but then take their space away. Forcing then to need to decelerate and solve the problem differently. We might do this by changes in pitch size/shape or location of defenders etc. This provides a physical stimulus, a technical challenge but also a perceptual challenge helping the athlete link their movement to the environment demands.

There are hundreds of examples with this and they all need to be adapted to be sport and if possible, individual specific.

RTP: In summary, what is the final message we should take to apply to daily S&C Coach with athletes, both from an evaluation and a training point of view?  

Rich: Pulling everything together, my recommendations this kind of process:

  1. Do an in depth task analysis of what your sport demands from a COD and Agility perspective.
  2. Understand they key technical aspects of COD performance and the performance and Injury conflict
  3. Understand the athletes constraints via the use of linear speed, COD deficit and Deceleration deficit testing. Add some movement analysis within these tests and a more subjective assessments of how they complete tasks during competition.
  4. Decide what you think the best plan is to move forwards, where are their weakness, their strengths, and what does and doesn’t need to change?
  5. Physically prepare the athlete to deal with the movement demands via strength training and pre-planned COD challenges
  6. Challenge the athlete to problem solve against defenders by setting up agility games where you adapt constraints. Focus of putting them into scenarios which challenge their natural style of problem solving.

This is obviously a quick overview. There are lots more things to it and lots of nuances. I’ll be writing more about these things are creating some resources, so if you are interested get in touch and sign up for some updates.