A 180-degree turn can be broken down into three different components:
1. An approach phase where the athlete accelerates up to an effective speed 2. An entry phase which is a maximal deceleration while the body begins rotation 3. An exit phase which is a maximal re-acceleration into the new direction
The approach is simply acceleration, the important skill here is the athlete’s ability to moderate their speed to match their deceleration abilities. This is the concept of affordances. The athlete must know “how fast can I move within the space I have but still be able to decelerate and complete the task”. “How long can I afford to accelerate for?”. The more an athlete is exposed to similar tasks and their vairations, the more attuned they will become to what velocities and strategies are optimal for the task. I refer to this in my key skills model as 'affordance based control'.
The Entry Phase
The entry phase is where most of the important technical features exist and is where you want to focus your coaching time. Interestingly, it is the component which we know the least about as deceleration remains poorly understood. In the entry phase, if you are slow, performance suffers. If you are fast, but end up in a rubbish position, performance suffers.
This isn’t saying that the re-acceleration isn’t important, just that the effectiveness in the re-acceleration is difficult without a good competent entry phase. Unless you just go slowly, which of course isn’t useful for anything!
“The deceleration component should begin as late as possible, but as early as required to suit each athlete’s deceleration capabilities”
If someone is an effective decelerator, they will start the deceleration late, brake over a short distance and end up in an effective position at the plant step. This means they can accelerate for longer, getting up to a faster speed on the approach and save time.
If they are a poor decelerator or they have approached from a long distance away (running at high velocities), they will begin the deceleration component early to spread the required impulse over more steps. This might be decelerating over 7 steps instead of 5. Remember, as late as possible, but as early as required to end up in an effective plant step position.
When the deceleration phase begins, the early steps should provide some braking force and facilitate early changes in the centre of mass (COM) and base of support (BOS) relationship. The COM should lower, and the BOS should move in-front, allowing the production of a shin angle which points behind you. The early phase of deceleration is where you will expect to see the highest GRF and braking impulse, but it is also kinematically key as the athlete needs to slam the breaks on, but also lower their COM effectively to optimise how effective each step can be. This is a challenging balance and means huge high speed eccentric strength demands.
One of the very first movements you’ll see as someone approaches these turns is a subtle drop or hang back of the inside shoulder. This is the start of the rotation, drop-in COM height and the BOS moving forwards. There are then steps between the first braking step and the last (the plant step) where these positions continue to be exaggerated. Once you start to identify this in athletes, you realise just how much impact having a pre-planned task has on early kinematics. It might be 6 or 7 steps away from the turn line the body starts to organise itself to optimise the movement. Hence why the time constraints in reactive movements are so impactful.
The COM and the BOS manipulation cannot be separated in our analysis. The main reasons we lower our COM is so our legs are able to reach different points on the ground and create greater direction-specific shin angles. The rotation component is important to help the later exit phase. Remember a key principle of the re-acceleration phase is to get to the sagittal plane fas early as possible. And the more rotation needed in the transverse plane at this stage, the harder that is to do. Once this entry phase has taken place where the COM has lowered, the BOS moved forwards and the body began to rotate towards the new direction, the athlete has a final ground contact before moving back into the original direction. This final ground contact is referred to as the plant step.
Remember that the role of each step in a change of direction such as this is to optimise the ability of the step following it to do its job. If the penultimate step (the final step prior to the plant step) doesn’t sufficiently reduce momentum (or the steps preceding it haven’t performed their role either), this will influence the position and loading of the plant step, increase injury risk and not do performance any favour either.
This overall phase is all about distributing work over a number of strides. Each stride used different skills and needs to produce force in slightly different planes, muscle lengths and speeds. The easiest step for the athlete to use if the plant. It is extended, stiff and easy to coordinate. So keep a close eye on if athletes look less competent during those approach steps and just rely on that final step to do too much work.
Four priorities to look for as the athlete enters the plant step:
Approximately 90 degrees or rotation (half of what’s required)
Lower COM height
Both legs with a shin angle facing the new direction
Work effectively distributed across strides up to the plant step
Once the penultimate step has maximised its braking force it may remain in contact with the ground and provide some vertical support to maintain COM height. This part of the movement is the only point within a 180 degree turn when the body will have support from both feet at the same time. This is because to optimise the shin angle of the plant step, the location of it must be outside the BOS where it can't effectively support the body mass. It is also logical for the penultimate step to remain in contact with the ground because the position which it requires to apply braking force, is similar to the position which it requires to optimise it's role in propulsion. Therefore, this same leg, at times without leaving the ground acts at the final braking step (penultimate step) and the first re-acceleration step (propulsion step). It's a good idea to look for how much shin roll there is here too. When the penultimate step makes initial contact and applied braking force, the most competent athletes won't then display a movement where that penultimate step shin angle continues to creep more and more vertically.
However, It is common for the penultimate step to lift slightly while the plant step is in contact with the ground. This is commonly seen in athletes whose COM has not been sufficiently lowered, insufficient rotation has taken place or the penultimate step location also isn’t optimised for re-acceleration potential.
If this leg executes its role effectively, the plant step can then occur with minimal stress and the transition between entry and exit is fast and effective. If this leg doesn’t effectively perform its role, the plant step is overloaded reducing the safety and the effectiveness of force application.
An effective plant step should be stiff, have a fast ground contact time and be the final step prior to the exit/re-acceleration phase. Anything that has been ineffective before that point will likely slow the ground contact time and reduce the effectivenes of force application.
Simplifying the role and muscular demand of each step looks like this:
Penultimate Step (Entry) = deceleration and an eccentric muscle action Plant Step = final deceleration and initial re-acceleration with a more ‘isometric’ muscle action Propulsion Step (Exit) = re-acceleration and concentric muscle action
The Exit Phase
The exit phase is simple. It is mainly going to be a product of your acceleration capabilities, the position you put yourself in during the deceleration phase and your ability to apply force effectively. The key here is that because its acceleration, it needs to occur in the sagittal plane. This is all the way from the foot, to the femur and pelvis and the upper body. In order to do this effectively, we want to see the upper body lead the movement by rotating to the new direction and alignment between the foot and femur pointing towards the target.
We don't want a reliance on frontal plane force production here or for the trailing plant step to have to go around the propulsion/inside leg because we haven't rotted enough. Simply, make it look as much like acceleration as possible.
In coaching it feels like there is loads to look at. But the simplest framework is to look at the exit and initiation of re-acceleration as it is a function of everything that has happened before it. Then simply work your way backwards until you find an error, then identify the earliest cause of that error by looking more closely at the entry phase and thinking about how it all interlinks.
Some simple priorities to take forward which make up part of my key skills model. You need to develop and want to see:
Work distribution across strides
Afforance based control
A sagittal plane propulsion step
These are your big rocks, all of the other relative limb positions, joint angles and ground contact times etc are components of the above.
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ABOUT THE AUTHOR
Rich is the founder of Strength Coach Curriculums and an S&C coach who specialised in multi-directional speed. He runs the S&C provision for Bristol Flyers Basketball and consults with clubs across the globe while also leading the MSc programme at the University of South Wales