Muscle Memory (or Muscle Science) is a phenomenon whereby it is much easier to regain lost muscle mass than it is to put on new (initial) muscle mass.
Shrinking muscle or losing gains is a fear that many gym goers and lifters fear.
- Back when I was in college I broke my ankle pretty severely. I spent 12 weeks on crutches and lost most of the muscle in my calf. In fact, the muscle had diminished so much that I would play with it and watch it fling back and forth like a pendulum. Once I was “back on my feet again” (literally), I was surprised at how quickly I regained the muscle in my leg.
- When guys walk back into my gym after taking months off from their training, I watch as their gains increase quite rapidly and their muscles grow so quickly, it’s like they never even stopped.
The reason: The arc of building muscle size and strength lies in your nuclei. Nuclei control protein synthesis. The more nuclei you have, the more protein you are able to turn into muscle. The first effect training has on your muscles is not actually growth; it’s to create more nuclei, which eventually facilitate the development of more tissue.
Further, our muscle fibers have satellite cells which donate myonuclei. The myonuclei allows the cells to grow larger. Once your muscle fibers get bigger, more myonuclei are required because they can’t regulate that size fiber any longer. They have reached their maximum limit or myonuclei domain. Resistance training induces permanent physiological changes to your muscle fibers. The first time you begin strength training, your muscles adapt and become bigger and stronger, which is facilitated by increasing the muscle nuclei (aka myonuclei).
Myonuclei are permanent. Although it was widely believed that once muscles started to atrophy, the cell death, or apoptosis, occurred and the myonuclei were removed. However, current studies have shown that the myonuclei still exist even after period of not training or inactivity. Previously untrained muscles acquire newly formed nuclei by fusion of satellite cells preceding the hypertrophy. Detraining or inactivity leads to atrophy, but not loss of myonuclei, The elevated number of nuclei in muscle fibers in a hypertrophic episode would provide for muscle memory and long-lasting effects of training. Because they are still present, these cells skip the process of creating new myonuclei, allowing atrophy and gains to occur at a faster rate than the initial gains. By skipping the first step of satellite fusion and nuclear donation, new nuclei increases new muscle protein synthesis.
Just like riding a bike…
When muscles shrink due to inactivity (i.e. when training is stopped for a significant amount of time), it is much easier to rebuild that lost or shrunken muscle. And it takes less time to rebuild that mass, than it took to build it initially.
New myonuclei in muscle fibers are added before any major increase in size during overload. Old and new nuclei are retrained during severe atrophy. The myonuclei are protected from the high apoptotic activity in inactive muscle tissue. So, even as muscle shrinks, the nuclei remain present.
If you are someone who has never trained before, then you do not have the accumulation of myonuclei, but it is easy to get, since basically everything we do is a stress. Unlike someone who is already training, who will find that it becomes harder and harder to stress the muscle out.
And although you may lose the muscle, you don’t lose the myonuclei. Any myonuclei accrued from previous training remains in the muscle fiber. So, even though your muscles have gotten smaller because you haven’t used them, you still have the results of your previous hard work – this being the myonuclei – so you can bounce back fairly easily.
When training is resumed, muscles are able to grow rapidly because the initial stage of adding nuclei is skipped and, once the nuclei are roused, they can set about synthesizing protein pretty quickly.
Muscle memory is also why physiologists recommend filling your muscles with as many nuclei as you can while you’re young. Building muscle gets harder as you age, whereas maintenance is easy. The type 1 fibers dominate when you get older, and the type 2 fibers (the fast-twitch fibers) tend to wane, but they’re still there.
So, get to the gym and take advantage of building myonuclei while you can. And just as importantly, if you’ve been pumping away for a while, afraid to take a break because of fear of loss of gains, go ahead and rest. It takes a very long time to lose the gains you’ve worked so hard to accrue. And, as per my recent post, Rest Days are just as important in attaining your goals.