- Roger Fielding
- The Conversation *
There is perhaps no better way to observe the absolute pinnacle of human athletic ability than by watching the Olympics.
But at this year’s Winter Games, and at just about every professional sporting event, you rarely see a competitor over 40 and almost never see an athlete over 50.
This is because with each additional year spent on Earth, bodies age and the muscles do not respond to exercise as well as before.
I lead a team of scientists studying the health benefits of exercise, strength training, and diet in older people.
We investigate how older people respond to exercise and seek to understand the underlying biological mechanisms that cause muscles to increase in size and strength after resistance or strength training.
The old and the young build muscle the same way. But as you age, many of the biological processes that turn exercise into muscle they become less effective.
This makes it more difficult for older people to build strength, but it also makes it that much more important for everyone to continue to exercise as they age.
how the body builds muscle
The exercise I study is the kind that makes you stronger. Strength training includes exercises like push-ups and sit-ups, but also weight lifting and resistance training with bands or exercise machines.
When you strength train, over time, exercises that seemed difficult at first become easier as your muscles increase in strength and size, in a process called hypertrophy.
The biggest muscles just have larger muscle cells and fibers and this allows you to lift heavier weights.
As you continue to exercise, you can continue to increase the difficulty or weight of the exercises as your muscles get bigger and stronger.
It’s easy to see that exercise makes muscles bigger, but what actually happens to cells as muscles increase in strength and size in response to resistance training?
Every time you move your body, you do so by shortening and lengthening your muscles, a process called shrinkage.
This is how muscles expend energy to generate force and produce movement.
Every time you contract a muscle, especially when you have to work hard to make the contraction, such as when you lift weights, the action causes changes in the levels of various chemicals in your muscles.
In addition to chemical changes, there are also specialized receptors on the surface of muscle cells that detect when you move a muscle, generate force, or alter the biochemical machinery within a muscle.
In a healthy young person, when these chemical and mechanical sensory systems detect muscle movement, they activate a series of specialized chemical pathways within the muscle.
These pathways, in turn, trigger the production of more protein that are incorporated into muscle fibers and cause the muscle to increase in size.
These cellular pathways also activate genes that encode specific proteins in cells that make up the contraction machinery of muscles.
This activation of gene expression is a longer-term process, with genes being turned on or off for several hours after a single bout of resistance exercise.
The overall effect of these many exercise-induced changes is to make your muscles bigger.
how muscles change
While the basic biology of all people, young or old, is more or less the same, there is something behind the lack of older people in professional sports.
So what changes in a person’s muscles as they age?
What my colleagues and I discovered in our research is that in young muscles, a little bit of exercise produces a strong signal for the many processes that trigger muscle growth.
In the muscles of older people, by comparison, the signal that tells the muscles to grow it is much weaker for a given amount of exercise.
These changes begin to occur when a person reaches around 50 years of age and become more pronounced as time goes on.
In a recent study, we wanted to see if changes in signaling were accompanied by any changes in some genes, and how many of them respond to exercise.
Using a technique that allowed us to measure changes in thousands of genes in response to endurance exercise, we found that when young men exercise, there are changes in the expression of more than 150 genes.
When we looked at older men, we found changes in the expression of only 42 genes.
This difference in gene expression seems to explain, at least in part, the more visible variation between how young and old people respond to resistance training.
Stay fit as you age
When you add up all the various molecular differences in how older adults respond to strength training, the result is that older people don’t gain muscle mass like younger people do.
But this reality should not discourage older people from exercising. If anything, you should encourage them to exercise more as they get older.
Exercise remains one of the most important activities older adults can do for their health.
The work that my colleagues and I have done clearly shows that although responses to training decline with age, they are by no means zero.
We show that older adults with mobility problems who participate in a regular program of aerobic and resistance exercise can reduce their risk of becoming disabled by approximately 20%.
We also found a similar 20% reduction in risk of disability among people who are already physically frail if they performed the same exercise program.
While younger people can get stronger and build bigger muscles much faster than their older counterparts, older people still reap incredibly valuable health benefits from exercise, including increased strength, physical function, and reduced disability.
So the next time you’re breaking a sweat during a training session, remember that you’re building the muscular strength that’s vital for maintaining mobility and good health for a long life.
*Roger Fielding is associate director of the Jean Mayer USDA Human Nutrition Research Center on Aging and professor of medicine at Tufts University. This article appeared on The Conversation. You can read the original version in English here.
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