Play enhances optimal movement variability. Optimal variability is necessary for an organism that wants to move in a complex environment. It is required for an animal that needs to be adaptive to survive and thrive in unpredictable situations. It is vital for pain-free functioning in an ever-changing world.
Music: Grant Green: Sookie Sookie
But what is movement variability? What is optimal and why is it important? How does play influence variability? Read on…
I’ll try to be as concise as I can. I’ll surely write some more on variability! For those intrigued by the topic, there’s quite a lot to find on movement variability, but I suggest to start with the articles cited at the end, all very worth of your attention. Quotes in my blog are from these articles.
A. What is movement variability?
“Movement variability is defined as the normal variations that occur in motor performance across multiple repetitions of a task.” If a person tries to do the same movement twice, it will never be exactly the same. Even if you try, no two steps will be identical. Bernstein is often quoted: “repetition without repetition”. In the past variability was considered to be noise and/or error, to be random and independent, and thus detrimental to task performance. It was thought that the person having more skill would show less variability and more consistency in behaviour.
We know that this is wrong, and that even the most skillful people have variability in their movement. Jordan, Messi, Ali, Federer, … all have variability in their motor patterns. Even highly controlled repetitive tasks, like dart throwing or occupational tasks, have considerable motor variability. Outcome consistency does not require movement consistency. This variability is not random, but patterned in a non-linear way.
B. Why is movement variability important?
“Humans are designed not only with variability but for variability” (Linda Fetters, 2010).
Variability is functional. Its proposed functions are:
adaptability to the complex environment
reducing injuries through spreading of loads on the tissues
augmenting neurological information through constant change
facilitates changes in the coordination patterns
Variability reflects multiple options for movement, providing for flexible, adaptive strategies that are not reliant on rigid programs for each task or for each changing condition encountered.
Reduced variability is a consistent sign of problems, is associated with disease, overuse injuries and pain:
On the level of the tissues: “Coordination with low variability causes forces to be distributed across small surface areas, possibly resulting in overuse injuries. In contrast, the variations present during relative coordination allow joint or tissue forces to be distributed, thereby minimizing the chance for overuse injuries.”
On the level of sensory information: “The lack of variability in movement leads to abnormal mapping of the sensory cortex, which subsequently disturbs motor function. These neural maps (both sensory and motor) are more complex when movement variability is present and less complex when variability is reduced. Movements with an optimal amount of variability avoid this abnormal mapping and essentially contribute to the neuroplasticity needed for maintaining or achieving functional skill.”
On the level of adaptability: “By reducing the number of available movement patterns, a less flexible system results that may not respond appropriately to an external perturbation. This prevents the biological systems to be adaptable and flexible in an unpredictable and ever-changing environment.”
Reduced motor variability may be characterized by a narrow range of behaviours, some of which may be rigid, inflexible and highly predictable. On the other hand, increased variability causes random, unfocused and unpredictable motor patterns. Increased variability makes the system unstable and sensitive to perturbations.
In other words, the development of healthy and highly adaptable systems relies on the achievement of the optimal state of variability.
“The lack of variability of action is a hindrance to the development of skilled, functional action, and excessive variability interferes with the production of automatic, dependable, and typical functional action.”
C. Optimal variability and good motor skill acquisition
So, if you learn movement, you would want to make sure that the result of your learning not only is an adequate movement pattern, but also has an optimal amount of motor variability within that pattern. But there’s more: variability facilitates changes in coordination patterns and thus enhances skill acquisition. Isn’t this nice? Good skill acquisition practice enhances variability, and variability enhances new skill acquisition! A kind of positive feedback loop! With restricted variability, the acquisition of skilled action also will be restricted.
“The suggestion is that individuals involved in skill acquisition should be more or less tolerant of variable movement patterns depending on the task at hand (…) Observations of variability in system behaviour may reflect the readiness of the system to change and may be exploited by the coach. Therefore, variability in movement patterns resulting from free exploration should be viewed as a very natural and necessary consequence of movement control and learning in some skills.”
“For skill acquisition, exploration – whether successful or not (in terms of performance outcome) – is always useful in restructuring task solutions. Experience of what is incorrect is important to the discovery of what is correct and is a vital component in the learner’s exploration of the workspace. Equally, a lack of any observable improvement in performance outcome is not necessarily considered indicative of an absence of learning. The aim of skill acquisition programmes should be to facilitate exploratory behaviour, not eliminate it.”
“The relationship between motor variability and performance is closely connected to motor learning. I has been proposed that an optimal strategy when facing an unknown movement is to allow for a generally ‘large’ motor variability in the beginning, and then preferentially correct those deviations that interfere with task goals, while allowing more variability in redundant or task-irrelevant directions.”
Exploration is key to good motor learning. Experimentation is essential for skill acquisition, skills that are adaptable and thus transferable to situations that are not exercised as so.
Learning of motor skills requires learning of rules, rather than memorizing specific motor patterns. When you are offered the same input all the time, you will learn, but the learned skill will not be flexible and will have no transfer to other movements than the one that is learned.
Compare it with learning the solution of a problem by heart versus learning the rules to solving the puzzle. If you know the rules, you can solve every other problem with similar demands.
“When each movement produces identical information, the system is not able to distill knowledge (rules) from these movements, which can be transferred to other movements or to movements made in a novel context.”
An analogy I use often with my patients: If a child has learned to ride her bike, to a sufficient degree, she will probably have difficulties riding on a bike she has never tried before. However, if that child has experimented with different bicycles, she will have distilled the essence of riding (pedaling, steering, balancing), the rules, and will probably have few problems trying another type of bike.
D. How does play influence variability?
Now that we’re this far into the story of variability and motor learning, you will probably now how play enhances optimal variability. Play, almost by definition, requires exploration and experimentation within a varied, complex environment (living and non-living). Play fosters creativemovement, maybe inspired by other movers, but surely self-initiated and self-motivated. Play is trial and error. Play is never exactly the same.
All of these play attributes make sure that play, the natural learning mode, enhances an optimal amount of movement variability. I’m sure Goldilock likes to play…
Thanks for reading and cheers,
Pieter
References:
Hamill et al (2012) Coordinative variability and overuse injury. Sports Med Arthrosc Rehabil Ther Technol
Stergiou & Decker (2011) Human movement variability, nonlinear dynamics, and pathology: is there a connection? Hum Mov Sci
Harbourne & Stergiou (2009) Movement variability and the use of nonlinear tools: principles to guide physical therapist practice. Phys Ther
Handford et al (1997) Skill Acquisition in sport: Some applications of an evolving practice ecology. J Sport Sciences
Mulder & Hochstenbach (2001) Adaptability and flexibility of the human motor system: implications for neurological rehabilitation. Neural Plasticity
Bartlett et al (2007) Is movement variability importand for sports biomechanics? Sports Biomechanics
Stergiou et al (2006) Optimal movement variability: a new theoretical perspective for neurological physical therapy. J Neurol Phys Ther
Fetters (2010) Perspective on variability in the development of human action. Phys Ther
Srinivasan & Mathiassen (2012) Motor variability in occupation health and performance. Clinical Biomechanics