We know the brain's role as the mission control centre for the building blocks of athletic skill training: strength, explosiveness, and short-term muscular endurance from previous Athlete's Guide to the Brain posts (i.e. executing at 100 per cent for a certain length of time). On the other hand, gymnastics requires gymnasts to master all of these factors simultaneously, as each routine requires combining a series of complex athletic movements to produce one seamless performance.
The brain learns sequences in three steps: encoding, consolidation, and retention. Thus, for example, a gymnast must practise a sequence over and over again until it becomes automatic for it to become a part of his or her "muscle memory." This generally translates to activation in the motor cortex while learning the sequence and activation in the cerebellum once the movement is mastered and no conscious effort is required.
Which begs the question: how do gymnasts begin to create complex movements like switch-leaps and back handsprings in the first place before mastering an intricate routine? Nothing in human DNA gives gymnasts the natural ability to do back handsprings in the same way that humans innately know how to crawl as babies. Unique, complex movements, such as those seen in gymnastics, necessitate a highly orchestrated tornado of thousands or millions of muscle fibres, making the brain's task of controlling movement extremely difficult.
According to a 2002 study by Bizzi and colleagues, the nervous system generates synergic muscle groupings that correspond to specific, complex movements to simplify control. In other words, a muscle "synergy" is made up of all of the simultaneous muscle activations that happen during a move. Consider all of the muscle patterns required in your fingers to tie your shoes, type on a keyboard, or play a musical instrument as an example.
According to a Classen and Gentner study published in 2006, each muscle synergy is encoded as one "module" in the motor cortex. So, let's say a back handspring necessitates the activation of 12 distinct muscle patterns (e.g. leg muscles for jump force, back muscles to bend, core for stability, arms to push off the ground, etc.). Instead of activating 12 different neuronal firing patterns, the modular system combines these patterns into a single master pattern or neural control module. Because only one neural module needs to be activated instead of 12, the handspring execution becomes faster and more efficient.
Consider motor neurons learning these groupings in the same way we learn to use collective nouns to refer to complex lists as children. So, for example, instead of listing every member of our family ("My mom, dad, brother, sister, dog, and I went to the park yesterday..."), we can increase efficiency by grouping each individual into a single group ("My family and I went to the park yesterday..."). Linguistically, this grouping reduces unnecessary jargon to make communication more timely and efficient — a process similar to the brain's process of compressing and simplifying complex movement.
The motor cortex encodes all of the muscle patterns required for a back handspring as a single module.
Let us expand on the concept of neural modules. If a single neural module represents a single movement, connecting a series of modules will result in a sequence of movements, similar to frames in a movie. Consider Aly Raisman's opening pass in the 2016 Summer Olympics as an example. When we dissect the past, we can see that her "modules" are as follows: a round-off, a one-and-a-half twist step out, another round-off, another back handspring, and an Arabian double front to punch layout to land. Thus, we can create a movie that connects Raisman's movements or sequences by stringing these modules together and fast-forwarding them.