There is perhaps no better way to see the absolute pinnacle of human athletic abilities than by watching the Olympics.

But at the Winter Games this year – and at almost all professional sporting events – you rarely see a competitor over 40 years old and almost never see a single athlete over 50.

This is because with every additional year spent on Earth, bodies age and muscles don’t respond to exercise the same as they used to.

We investigate how older people respond to exercise and try to understand the underlying biological mechanisms that cause muscles to increase in size and strength after resistance or strength training.

Old and young people build muscle in the same way. But as you age, many of the biological processes that turn exercise into muscle become less effective.

The exercise I study is the type that makes you stronger. Strength training includes exercises like pushups and sit-ups, but also weightlifting and resistance training using bands or workout machines.

When you do strength training, over time, exercises that at first felt difficult become easier as your muscles increase in strength and size – a process called hypertrophy.

Bigger muscles simply have larger muscle fibers and cells, and this allows you to lift heavier weights.

It is easy to see that working out makes muscles bigger, but what is actually happening to the cells as muscles increase in strength and size in response to resistance training?

Any time you move your body, you are doing so by shortening and pulling with your muscles – a process called contraction.

This is how muscles spend energy to generate force and produce movement.

In addition to the chemical changes, there are also specialized receptors on the surface of muscle cells that detect when you move a muscle, generate force or otherwise alter the biochemical machinery in your muscles

These pathways in turn trigger the production of more proteins that get incorporated into the muscle fibers and cause the muscle to increase in size.

The overall effect of these many exercise-induced changes is to cause your muscles to get bigger.

While the basic biology of all people, young or old, is more or less the same, something is behind the lack of senior citizens 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 muscle, a little bit of exercise produces a strong signal for the many processes that trigger muscles growth.

These changes begin to occur when a person reaches around 50 years old and become more pronounced as time goes on.

In a recent study, we wanted to see if the changes in signaling were accompanied by any 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 partly, the more visible variation between how young and old people respond to strength training.

When you put together all of the various molecular differences in how older adults respond to strength training, the result is that older people do not gain muscle mass as well as young people.

We also found a similar 20 percent reduction in risk of becoming disabled among people who are already physically frail, if they did the same workout program.

While younger people may get stronger and build bigger muscles much faster than their older counterparts, older people still get incredibly valuable health benefits from exercise, including improved strength, physical function and reduced disability.

So the next time you are sweating during a workout session, remember that you are building muscle strength that is vital to maintaining mobility and good health throughout a long life.

(This is an opinion piece and the views expressed above are the author’s own. FIT neither endorses, nor is responsible for them. This article was originally published on The Conversation. Read the original article here.)