18 Feb Muscle Memory and Repeated Bout Effect

What is Muscle Memory?

When people refer to muscle memory, they typically speak about movement coordination stored in the motor cortex and basal ganglia rather than the muscle—like riding a bike or shooting a basketball. For instance, if I were to play a pick-up game of basketball after years away, I might seem uncoordinated at first because my brain and body need time to re-establish the coordination required for dribbling and shooting. This is wrongfully termed muscle memory. However, another type of ‘muscle memory’ is often overlooked, and it is referred to it as repeated bout effect (RBE).

Why It Matters: 

A recent review article published by Calvo-Rubio (2024) discusses RBE extensively, going through the process that your muscle experiences during eccentric contractions and the damage incurred, followed by recovery. Where ‘muscle memory’ comes into play is how your muscle recovers. When a muscle is exposed to a repeated stimulus, the damage experienced and the inflammatory response become less over time. Whenever someone starts a new training block, they usually report a lot of soreness the first week. Then, in the successive weeks, they will not feel nearly as sore, if at all, because the muscle’s ability to recover improves. You may notice the same effect on your training.

What I find interesting about this paper is that this adaptive response persists even after extended periods without training, meaning your muscles retain a form of ‘memory’ of past stressors. This memory manifests in two key ways:

1. Myonuclei Retention: As we train, muscles accumulate new nuclei (myonuclei) within the muscle fibers, which remain even after long periods of inactivity. These nuclei facilitate quicker adaptation and growth when training is resumed.

2. Epigenetic Modifications: Specific gene expressions are modified during training, enhancing the muscle’s response to future stress and promoting better adaptation during retraining (Calvo-Rubio et al., 2024).

Essentially, ‘muscle memory’ occurs in the muscle’s ability to adapt to training rather than in its coordination. RBE has excellent implications for long-term fitness and aging, highlighting the potential to retain adaptations and regain strength after time off. Understanding this form of muscle memory can help guide more effective and sustainable training approaches.

Reference

Calvo-Rubio, M., Garcia-Domiguez, E., Tamayo-Torres, E., Soto-Rodríguez, S., Olaso-Gonzalez, G., Ferrucci, L., de Cabo, R., & Gómez-Cabrera, M. C. (2024). The repeated bout effect evokes the training-induced skeletal muscle cellular memory. Free Radical Biology and Medicine, 225, 247–254. https://doi.org/10.1016/j.freeradbiomed.2024.09.047