There is perhaps no better way to see the absolute pinnacle of human athletic ability than by watching the Olympics. But at the Winter Games this year – and at almost every professional sporting event – you rarely see a competitor over 40 and almost never a single athlete over 50. Indeed, with each additional year spent on Earth, bodies age and muscles do not respond to exercise in the same way as before.
I lead a team of scientists studying the health benefits of exercise, strength training and diet in the elderly. We study how older people respond to exercise and try to understand the underlying biological mechanisms that increase muscle size and strength after resistance or strength training.
Old people and young people develop their muscles in the same way. But as you get older, many of the biological processes that turn exercise into muscle become less efficient. This makes it harder for older people to build strength, but it’s also that much more important for everyone to continue exercising as they get older.
How the body builds muscle
The exercise I’m studying is the type that makes you stronger. Strength training includes exercises like push-ups and sit-ups, but also weight lifting and resistance training using bands or exercise machines.
When you do strength training, over time, exercises that seemed difficult at first become easier as your muscles increase in strength and size – a process called hypertrophy. Bigger muscles simply have bigger fibers and muscle cells, allowing you to lift heavier weights. As you train, you can keep increasing the difficulty or weight of exercises as your muscles get bigger and stronger.
It’s easy to see that training makes muscles bigger, but what actually happens to cells when muscles increase in strength and size in response to resistance training?
Every time you move your body, you do so by shortening and pulling with your muscles – a process called contraction. 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 lifting 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 are moving a muscle, generating force or otherwise. alter the biochemical machinery in a muscle.
In a healthy young person, when these chemical and mechanical sensory systems detect muscle movement, they activate a number of specialized chemical pathways in the muscle. These pathways in turn trigger the production of more protein which is incorporated into muscle fibers and increases muscle size.
These cellular pathways also activate genes that code for specific proteins in the cells that make up the muscle contraction machinery. This activation of gene expression is a longer-term process, with genes being on or off for several hours after a single session of resistance exercise.
The overall effect of these many exercise-induced changes is to make your muscles bigger.
How older muscles change
While the basic biology of all people, young or old, is more or less the same, something lurks behind the lack of seniors in professional sports. So what changes in a person’s muscles as they age?
What my colleagues and I have found in our research is that in young muscles, a little exercise produces a strong signal for many processes that trigger muscle growth. In the muscles of the elderly, by comparison, the the signal telling muscles to grow is much weaker for a given amount of exercise. These changes begin to occur when a person reaches around 50 and become more pronounced over time.
In a recent study, we wanted to see if changes in signaling were accompanied by changes in which 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 resistance exercise, we found that when younger 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 strength training.
Stay fit as you age
When you put together all the different molecular differences in how older people respond to strength training, the result is that older people do not gain muscle mass as well as younger people.
But this reality should not discourage older people from exercising. On the contrary, it should encourage you to exercise more as you get older.
Exercise remains one of the most important activities seniors can do for their health. The work that my colleagues and I have done clearly shows that while responses to training decline with age, they are by no means reduced to zero.
We have shown that older adults with mobility issues 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 the risk of becoming disabled in people who are already physically fragile if they followed the same training program.
While young people can get stronger and build bigger muscles much faster than their older counterparts, older people still reap incredibly valuable benefits from exercise, including improved strength, physical function, and reduced disability. So the next time you sweat during a workout, remember that you’re building muscle strength that’s essential to maintaining mobility and good health throughout your life.
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