Here is another great question that I get asked a lot as a personal trainer. Do muscles have a memory? When people ask this, they usually refer to either of the following: 1) motor learning or 2) gain and loss of muscle size. These are two different things, so let me explain both before I answer the question.
According to the Merriam-Webster dictionary, motor learning is “the ability to repeat a specific muscular movement with improved efficiency and accuracy that is acquired through practice and repetition.” Your nerves have learned in which order to activate your muscles in order to perform a certain movement. A movement involves a complex sequence of tensing and relaxing many different muscles. Over time, with continual practice, actions as complicated as riding a bike, knitting, or even playing a tune on a musical instrument, can be performed almost automatically and without thought. So the processes that are important for learning, and the memory of new skills, occurs in the brain, not in the muscles. Motor learning is a relatively permanent change in the ability to execute a motor skill as a result of practice and experience.
If you want to know more about which areas of the brain are involved and grow in the process of learning a new motor skill, you can check out this article from Oxford University.
Muscle cells contract and relax together to move the body. Muscle cells contain filaments of protein that slide over each other to cause a muscle contraction. They are arranged in such a way that makes them look like bands. They contain a lot of mitochondria (the power house of a cell) which provide the energy for the muscle contraction. Cells also have a “control centre” which are called nuclei. In muscle cells, these are called myonuclei. Muscle cells are quite large and one of the few that actually can contain more than one nucleus.
When you train a muscle to grow bigger, after you workout, your body repairs or replaces damaged muscle fibers. Not only that – your body increases the number of new muscle protein strands and their thickness. This creates muscle hypertrophy (growth).
Studies show that new myonuclei are added before an increase in muscle size during overload (training).
That is because the area that one myonucleus can “oversee” is limited. So if the area within a muscle fibre is growing, the cell needs to produce more myonuclei. The number of nuclei within the muscle fibers is one of the most important factors that determine muscle size.
Although muscle “memory” is more suitable to describe motor learning as explained above, the term is also often used in the context of regaining muscle after a period of atrophy (muscle loss). When we stop training for an extended period of time, we know by looking in the mirror that our muscles shrink, and we eventually look like we never lifted a weight. When we detrain (do not train), the muscles become smaller and weaker. But the myonuclei that we acquired when we trained and caused muscle hypertrophy the first time, are being retained in the muscle cells (there is some evidence that we actually never lose them).
This basically means that strength training is longterm. These myonuclei are retained even when the muscles are inactive for a while, so retraining is easier and requires less time as the step of adding new nuclei is skipped – the nuclei are already in place and ready to synthesize muscle proteins, which results in a quick increase in muscle size.
So, to answer the question: Yes, muscle memory does exist. And it’s so awesome! Because it means that all the hard work we put into staying fit and strong stays with us for the rest of our lives. The younger we start doing this the better, as muscle building is easier at a younger age. Muscle loss is a major health risk when we get older. And, as we all know, life happens and sometimes we are forced to take a break from training, but knowing that the “gains” will come back easier the second time around is certainly less discouraging!