A growing body of research suggests that the effects of physical activity, particularly from a young age, could have more beneficial effects on maintaining or regaining muscle mass later in life than previously believed.
And that means the old “use it or lose it” dogma isn’t quite right.
In a review published last week in Frontiers In Physiology, Lawrence Schwartz, PhD, a professor of biology at the University of Massachusetts, Amherst, describes the evidence for this actual “muscle memory” as it is demonstrated in animal and insect models.
He notes, however, that while promising, these results are not directly comparable to humans yet.
Muscles are special cells in that they are incredibly plastic. They can grow or shrink at will depending on living conditions. Physical exercise is an obvious example that can cause hypertrophy (muscle growth), resulting in muscle fibers that can be 100,000 times larger than an average cell in the body. On the other hand, malnutrition or a sedentary lifestyle can cause muscles to shrink (atrophy).
Single cells only contain one nucleus, but during hypertrophy, cell growth cannot be sustained by a single nucleus, so muscle cells actively recruit nuclei from surrounding cells.
Just as these nuclei come together during muscle growth, they are also believed to die off if the muscle shrinks, a theory known as the “myonuclear domain hypothesis.”
In a new study by Schwartz, he argues that nuclei must maintain a certain ratio with the volume of the cell: Hypertrophy requires more nuclei while atrophy requires less.
According to the research reviewed by Schwartz, the evidence suggests that these additional nuclei actually persist through atrophy, allowing individuals to “bank” these additional nuclei in their muscle cells to be drawn on later in life.
“If this is generalizable and it looks like it is, then once you acquire a nucleus you get to keep it,” Schwartz told Healthline. “Well it’s a whole lot easier to acquire those nuclei when you’re young and fit.”
At that time “you have a very rich what’s called satellite pool or stem cell pool of cells, that can contribute their nuclei to the muscle,” he added. “So it’s easier to bulk up when you’re young rather than old, and we’ve all seen that.”
According to Schwartz a more accurate dogma should be “use it or lose it… until you use it again.”
While this research is still in the early phases, it joins other studies that have found evidence of muscle “memory.” Last year, a study that involved eight human subjects, found that muscles may develop certain genetic markers during exercise that may help muscle growth later in life.
The early evidence from this research is that those who have spent time working out will have an easier time getting back any lost muscle.
These study findings mean that even though muscle atrophy can happen within a couple of weeks, a person who worked out in the past will likely have an easier time rebuilding muscle than a person who never worked out.
“Once an athlete always an athlete,” said Dr. Nadya Swedan, physical medicine and rehabilitation specialist at Lenox Hill Hospital in New York. “I think it’s definitely harder for someone who never exercised to get into exercise later in life, than someone who exercised, took a break, and then comes back to it.”
Swedan is not affiliated with the research.
Understanding how to improve muscle growth could help improve the health of countless patients.
Muscle atrophy related to aging, known as sarcopenia, as well as other reasons including stroke, amyotrophic lateral sclerosis (ALS — also known as Lou Gehrig’s disease), or just sedentary behavior are all associated with various health problems.
Sarcopenia, particularly in older individuals, can reduce independence by affecting mobility. It’s also associated with greater all-cause mortality risk and rheumatoid arthritis.
It's Never Too Late
Healthline’s guide on fighting back against sarcopenia offers insights as well as practical steps you can take to help get back into shape, including exercise and diet recommendations.
Whether you’re middle age or an astronaut, muscle loss is a serious but modifiable condition that can be affected by day-to-day activity.
Swedan says this study should be encouraging.
“You can indeed at any age improve your muscle function. To have this study as proof is pretty cool for people to know that,” she said.
The study should also serve as a call to action for parents and children alike: Getting out and being physical at a young age could prove more important now than it’s ever been, especially if it means being healthier in old age.
“If you’re very active and fit when you’re young, even if you get out of the habit of exercising, you banked potentially those extra nuclei, and when you come back to it, you can get a level of fitness that would be hard to achieve if you were doing it for the first time,” said Schwartz.
Written by Gigen Mammoser on February 1, 2019