"Muscle memory" is a frequently used term to describe the learning of motor skills, be they sport, music, or everyday activity. But interestingly, despite the widespread usage of the term, controversy exists as to its accuracy.
Muscle memory commonly describes the situation whereby people seem to quickly regain a previously under-utilised or "forgotten" skill. If I hear another person return from the snow resorts saying:
you wouldn't believe it, I haven't skied in 15 years and yet skied as if I had never left the mountain!
It's impossible to cover all the questions relating to muscle memory so I will limit this article to two key topics:
1. Do muscles really have a memory?
2. Why is it that skills such as skiing and bike-riding seem relatively easy to retain, while others such as golf or playing music are not?
Flexing the definition
Scientists approach muscle memory from a variety of perspectives based on the measurement and analytic tools they use.
- Cognitive psychologists cite the centrality of the brain in any muscle memory (learning) that takes place.
- System theorists (the multi-disciplinary consideration of physics, biology, chemistry and maths) discuss the self-organising nature of the human movement system and the importance of the environment in which we act.
- Neuroscientists discuss neural plasticity and the strengthening of synaptic connectivity as a function of repetitive firing through practice. Consolidation of such processes is a related issue with the role of sleep in motor learning a current hot topic.
- Neurophysiologists attack the question from first principles: "Can muscles really drive behaviour independent of the nervous system?"
In all cases, these scientific disciplines would generally reject the idea of muscle memory in the literal sense that the term is generally used.
As a scientist interested in sports skill acquisition, my definition of muscle memory is that it's a colloquial term used by practitioners to describe the complex process of learning and retaining a motor skill.
First, a skill needs to be learned. Then, once learned, the question becomes: how well is the skill retained over time?
Retention of a motor skill, which is an index of the quality of the original learning, can manifest itself as changes in:
- limb-segment coordination (preferred coordination patterns)
- the neuromuscular system used to perform the skill and how the various component processes are activated, the amount of conscious attention used to control the skill (noting that skills can be learned without conscious attention)
- the knowledge structures used to guide their performance (such as tactical awareness).
Any or all of the above qualities may become degraded or retained over the life-cycle of a motor skill. So the term "muscle memory" simplifies the complexity of the processes involved in the learning and subsequent retention of a motor skill.
A moving target
The retention of all motor skills is not equal. As already mentioned, skills such as skiing and riding a bike seem remarkably robust to forgetting, whereas others – a golf swing or a series of discrete movements, such as when playing the piano – tend to dissipate more quickly.
While the number of theories and strategies that can be employed to improve the permanency of a motor skill and protect it from forgetting is a significant field in its own right, some general points can be made.
The most obvious difference is the sheer volume of practice one can achieve completing a continuous-type skill, such as cycling, relative to a more discrete skill, such as hitting a golf ball.
Even if you hit a bucket of golf balls at the range you may only complete 100 or so practice repetitions. By contrast, going for a bike ride for an equivalent period of time would produce significantly more repetitions.
This repetition value is a key reason why professional golfers hit as many as 600 balls in a practice session, or why musicians "over-practice" each piece they are trying to consolidate.
The context-specificity of the practice of such skills also varies. Practising at the golf range doesn't provide the same environmental conditions faced on the course. In contrast, cycling practice is more likely to provide a closer coupling between the skill and the performance setting more of the time (so stay off the fixed exercise bikes!).
Furthermore, the spacing of repetitions of different but similar skills becomes critical. In the case of a pianist, learning one complex finger sequence and then immediately switching to another may cause interference and result in loss of the first sequence practised.
It is even suggested pianists avoid leaving practice and immediately tapping away on the computer for similar reasons.
Motor learning is considerably more than just muscle memory. It relies on the establishment of complex neural networks throughout the human movement system fostered through considered practice repetition in appropriate environments.
Much is still to be learnt about these processes and importantly how educators can improve the quality of motor skill learning and retention from childhood through to sports expertise.