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. This makes it harder for older
people to build strength but also makes it that much more
important for everyone to continue exercising as they age.
The exercise I study is the type that makes you stronger.
Strength training includes exercises like pushups and situps,
but also weightlifting and resistance training using bands or
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. As you keep working out,
you can continue to increase the difficulty or weight of the
exercises as your muscles get bigger and stronger.
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. Every time you contract a muscle -
especially when you have to work hard to do the contraction,
like when lifting weights - the action causes changes to the levels of
various chemicals in your muscles. 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 within a muscle.
In a healthy young person, when these chemical and mechanical
sensory systems detect muscle movement, they turn on a number
of specialized chemical pathways within the muscle. 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.
These cellular pathways also turn on genes that code for
specific proteins in cells that make up the muscles
contracting machinery. This activation of gene expression is
a longer-term process, with genes being turned on or off for several hours after a
single session of resistance exercise.
The overall effect of these many exercise-induced changes is
to cause your muscles to get bigger.
How older muscles change
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 muscle growth. In
older people's muscles, by comparison, 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 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
Staying fit as you age
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.
But this reality should not discourage older people from
exercising. If anything, it should encourage you to exercise
more as you age.
Exercise still remains one of the most important activities
older adults can do for their health. The work my
colleagues and I have done clearly shows that although the
responses to training lessen with age, they are by no means
reduced to zero.
We showed 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 about 20%. We also found a similar 20%
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 article is republished from The
Conversation, a nonprofit news site dedicated to sharing
ideas from academic experts. It was written by: Roger