Understanding Movement Error

What causes movement error?

There are several possible causes, and many more we won’t talk about here – but primarily movement error can be;

1. Errors in the movement pattern being sent down from the brain
2. Proprioception and responses not being well ‘automated’ for this pattern
3. Problems with the hardware (musculoskeletal system) causing a good pattern to be skewed when it is delivered to the muscles
4. Fatigue of the muscles from either a lack of ATP (energy system fatigue) or lack of neural input (neuromuscular fatigue) which can be caused by less neurotransmitter being available

How can an initial movement pattern in the brain be wrong?

Fundamentally initial movement pattern errors are either from

1. A lack of refinement - it could be that the person is still learning the movement
2. The incorrect refinement taking place - it can be that the movement they have learnt is incorrect. 

In the first situation it’s possible the correct pattern hasn’t been practiced often enough to be ingrained.  This means lots of slow and careful execution of the movement may be required; lots of reps, concentrate on good safe technique to bed the right pattern in. 

In the second situation a movement may have been refined when either the brain has had

1. To work around a musculoskeletal problem (pain, stiffness, injury) or
2. Has had the wrong movement aim given to it or
3. Has achieved a movement aim without the movement being of quality 

In the first case, where pain is present for instance, the brain will work the body into a position where it can complete the task, but it may be the wrong position to be in over the longer term.  The danger here is that the body learns the new position and locks it in to the pattern. 

An example is someone with low back pain.  In order to walk they will sometimes shift their spine away from the pain (a lateral shift) which makes them look like they are walking in a western movie slinging one leg around the other with their belt line all tilted.  If they do this for a while, even after the back pain is gone, they may still retain some of this new posture when they are walking. 

In the second case, where the movement result meets the stated aim for the brain, the brain may have been given the wrong aim.  You can see this with resistance exercises. 

If you tell a person to get their legs parallel to the ground in a squat or deadlift they will.  They may not have the strength to do it correctly, with the trunk upright and spine in a neutral position, but they could do it by flexing forward at the waist.  So, because you’ve given them one aim, get your thighs parallel to the floor, their good old brain has set that as the movement aim and has achieved it.  The problem is you have created a very unsafe pattern and in just ten gym sessions (with say 30 squats or deadlifts in a session) this pattern will be influencing their primary squat pattern, particularly when they see a bar and weight plates in front of them. Injury is unfortunately inevitable.

In the third case, where a good result is achieved but the movement quality is poor, the brain is fooled by the outcome.

Think of the weird golf swings you might see that actually result in quite a good shot.  Or the person who shoots a basketball with their elbow out to the side.  The outcome may be favourable (ie the shot goes in) but how reliable or desirable is the pattern in the long term.  What happens when the person has to shoot the basketball on the move, will they be able to control the ball well with the elbow out?

The upshot of all this is that people should only train independently when they are

1. Pain free
2. Properly warmed up (full range, nervous system on, specific movements to the body of the workout as part of warm up etc)
3. Correctly patterned
4. With movement limitations prescribed for

This final point is not to be overlooked.  Some people will be able to maintain a healthy primary pattern only within certain ranges due to musculoskeletal limitations (connective tissue tightness for instance).  Usually a brain will pick up within a few days what is being asked of it, but it will take time to achieve the correct movement if it is faced with hardware that really isn’t in good condition. 

So, when you prescribe exercises keep in mind the need to limit ranges of movement and allow the tissues time to lengthen and strengthen to cope.  Get the person correctly patterned and instead of setting ‘more weight’ as a goal you may instead ask for ‘more range’.  Again, as a trainer you are thinking long term value as well as short term gains.

Why wouldn’t our reactions for a movement be good?

Proprioception and reactions for a movement develop over time and become automated.  The key here is that the ability of a person to complete a movement quickly and efficiently in a broad variety of circumstances is dependent on their practicing that movement in those circumstances.  This gives the body (in this case particularly the sensory nervous system) the chance to experience what is required and tell the brain.

Just as it takes a child time to programme in the spinal reflexes for walking it can take time for a person to develop reflexes for primary movement patterns where you are loading, changing, or manipulating the external environment.  Once the reflexes are up to date, the performance of the pattern improves in that circumstance.

In a gym scenario you can see this when someone is learning to do the bench press for the first time after previously using the chest press machine.  They tend to shake and be unsteady with the bar.  They can take the load, they can probably do a few push ups, but what they haven’t yet got programmed in is all the little reflexes involved in keeping that bar straight, over their chest and moving evenly at the right pace.  It usually takes just a few sessions for the brain to learn and programme in these responses.

Another example is one where the reactions are there but you need new levels of control to execute the same movement at higher speeds or loads.  If the programming of the ‘reactions’ that allow the movement to be executed at higher loads or speeds hasn’t occurred, then when you speed the movement up you see errors.  This means practice is required, gradually speeding up or loading the person, and opening up the skill (making the skill less predictable). 

An example might be taking a jump shot in basketball which is well patterned and then making the athlete do it more and more quickly helping their body build up the reactions required to control the shot coming at pace from the right or left hand side of the court.  This is a common approach to skill acquisition in intermediate level sports.

Why can a good pattern go bad – a musculoskeletal system under-prepared?

A very good initial movement pattern can be sent from the brain, with all the required reflexes programmed and ready to go but it can all come unstuck if the hardware (muscles, tendons, ligaments and joints) isn’t in good condition or ready.

When a set of messages are sent down from the CNS to execute this well known primary pattern the exact movement that occurs depends on the state of the system trying to carry out the orders. 

If a particular muscle is tight it will be more active than it should be during that movement because, as we learnt in the nervous system, the nerves can already be excited (already slightly depolarized) and fire off sooner or more frequently than desired.  In this situation we call those muscles ‘facilitated’ because they are already a little wound up.  When this happens there is bias created and the movement might not look as it should. 

You could also have muscles that are too relaxed, meaning they don’t fire early enough or frequently enough again affecting the movement. 

In order to prevent some of this biasing of the pattern a good warm up that includes movements at speeds/loads specific to the performance will allow the nervous system to adjust.

The other challenge for the musculoskeletal system is injury or pain.  Remember that any injured muscle, joint with pain or inflammation, or even tight connective tissue can all have an inhibitory or excitatory affect on the muscle. 

These protective mechanisms are built into the musculoskeletal system to prevent further injury.  After all an already torn muscle, inflamed joint or tight tendon won’t respond well to force.  So, the sensory nervous system could be ‘inhibiting’ activation of the muscles involved or be causing ‘over-activity’ in some muscles.  The result is usually a modification of the movement as it reaches the muscles. 

Given the number of possible ‘errors’ and their sources you would wonder how a movement ever occurs that looks ‘normal’.  The reason that movement resembling ‘normal’ can occur over and over again is that the brain is very task focused (wants to get the job done) and is very quick to respond.

Taking the pain example again, the person with back pain, who wants to walk to the dairy to get food, will be able to do so as long as the body moves its posture into a position where the pain isn’t too great and one leg can move past the other.  So, movement occurs in many instances despite pain, tightness, patterning errors and so on. 

Here’s the rub though.  As you increase the demands on the body and its movements you gradually see these errors show through and then you either need to back off, correct them, or continually risk injury.

Why our brains can hurt us – fatigue and focus?

The final reason that movement gets ‘sloppy’ is that the muscles being asked to complete the movement fatigue or the person completing the exercise loses focus/concentration. 

Muscular fatigue is actually the goal of some training so sloppy movement will eventuate if you train someone to ‘failure’ and don’t support them properly. 

This fatigue can occur from either energy system fatigue (ie there isn’t enough ATP present in the muscle to maintain the contraction) or neuromuscular fatigue / intervention (the nervous system can not maintain the contraction due to neurotransmitter shortage.

The key is that a good trainer will watch very closely the changes happening when the client is lifting and will spot and continue to extend the client only when it is safe to do so.  Note, that training clients to failure is not necessary to make progress.  Research has shown that you don’t need to train someone to failure to stimulate change.  You simply need to introduce enough overload to cause some change.  Then keep progressing that overload over time.

Remember, the brain is very ‘task’ focused so if you tell it to raise something above your head it will do that and use whatever technique it needs to accomplish the task.  It will change a lift to make it easier as soon as it gets feedback that the loading is a problem and/or that the muscle is starting to fail.  Fundamentally, your brain is a very obedient instigator interested only in a final result that matches your initial instructions / aims.  As a person nears failure within a primary movement the brain does several things – it does this to achieve the aims you have given it, it does not know inherently what ‘good’ or ‘bad’ technique is it is solely focused on the original aim.