Do muscles really have the power of memory?

Going back to the gym after a break is hard. It doesn’t matter if you’ve been training every day for five years: the first day back after a holiday or a long weekend, you’re going to suffer as if you were going for the first time. That’s when you’ll hear the motivational magic phrase: “Come one, muscles have memory!” A monitor will say it with conviction and assure you the next time will be easier because you have “heart” and your muscles will reward you for your dedication and discipline in the gym.

Aaron Santos is a personal trainer and he has often delivered those words of consolation. “I’m referring to the brain’s ability to remember movement patterns and send the correct command to the muscle. The longer you’ve trained, the more internalized those movements will be in the brain. If you stop training for a month, the first few exercises will take it out of you a bit, but after 10 minutes you’ll be back in the groove.”

Does muscle memory actually exist or is it a white lie used by trainers? Apparently, there is some truth to the idea that certain patterns of movement can be ingrained, much as the old saying goes that you never forget how to ride a bike. However, recent investigations into the literal meaning of the term suggest that there is in fact a capacity for memory in muscle fibers.

These studies demonstrate that the nucleus of a muscle cell does seem to have its own memory, beyond the memory of motor neurons, which are instead more a merit of the brain. In 2010, a study using mice demonstrated that the nuclei of muscle cells that multiplied in response to a period of heavy exercise did not disappear during periods of inactivity, but were retained in the muscle fibers waiting to be reactivated by another session.

Experts believe that this mechanism is replicated in humans and that, even if we cease to do exercise, the muscle cell nuclei are preserved and muscle growth will begin again when exercise does. This conceptual change has allowed some muscles atrophied through injury or disease to be retrained despite being considered lost.

Muscle memory linked to gene adaptability

Diego Jerez, a personal trainer, explains: “Muscle fibers are cylindrical and elongated and their nuclei multiply with training. With bodybuilding work, the fibers thicken and create new nuclei that are retained even if you stop training and the muscle goes back to its previous dimensions. When you get back into the gym - and this is why muscle is said to have memory - you gain muscle mass three times faster because those cores are already built from previous workouts.”

Another theory suggests that the origin of muscle memory lies in the way that genes adapt to their environment. Physical activity appears to produce certain proteins in muscle cells that facilitate their growth. In the long term, these changes could enhance muscle memory.

In either case, the amount of physical activity is what determines the power of muscle memory. In the absence of exercise, it goes without saying, there is little to remember.

A recent investigation into the impact of resistance training in men between the ages of 50 and 70 even goes so far as to suggest that muscle memory can be long-term. The study analyzed the effects of a resistance routine (exercises that are designed to increase strength and endurance) followed by a rest period and then another session. Each phase lasted for 12 weeks. The results showed that the training increased strength and power by between 10% and 36%. During the rest period, there was a loss of strength and power of between 5% and 15%. However, and this was the great revelation of the investigation, the maximum physical levels of the first session were recovered after just weeks of the second.

Put another way, only two months were required to recover the initial strength levels of the first period of training following three months of inactivity. The authors of the study concluded that the speed with which physical fitness is recovered depends on the previous fitness state of the person in question, the length of the rest period, age and the length of the retraining period. The better someone’s physical fitness and the longer the second period of training, the greater muscle memory is.

Muscle memory is like having a healthy savings account, with the uniqueness of never knowing how much you’ve got in the bank until you start training again.