We all know that muscular weakness and wasting will eventually
catch up with us because a decline in physical vigor is an inevitable part of the
aging process. After all, we have
seen our parents and grandparents slowly deteriorate, and many studies show a
correlation between aging, muscular weakness, and loss of lean muscle mass. Might as well just accept it . . .
right?
But what if the frailty that we see in senior citizens is mainly
due to a sedentary lifestyle, and the loss of muscular strength and endurance is
the result of disuse? What if the progression
from vitality to frailty is just a self-fulfilling prophecy?
Surprisingly, it has been shown that sitting on our fannies
is a significant factor in the aging syndrome—perhaps the major factor. Some pretty remarkable studies indicate
that lean muscle mass and strength, as well as muscular and cardiovascular
endurance, may be maintained well into advanced age.
But before we get into the juicy details, first some
vocabulary and basic concepts.
Physical fitness can be assessed different ways, but the two
we are most familiar with are cardiovascular function and musculature.
Cardiovascular Function.
The most widely used measure of cardiovascular fitness is “V02
max,” the maximum amount of oxygen that is available for the performance of a task. V02 max is generally measured by having the
subject run on a treadmill while wearing a mask that delivers oxygen and tracks
consumption. For those of you who
don’t have a treadmill and an oxygen mask readily available, you can estimate
your V02 max as follows: divide your maximum heart rate by your resting heart rate and
multiply by 15. The result is an
estimate of your V02 max.
The average
untrained male has a V02 max of 35-40 ml/kg/min, meaning that he
consumes 35 to 40 milliliters of oxygen per kilogram of weight each minute. Elite male runners can consume 85
ml/kg/min. Remarkably, thoroughbred horses have a
V02 max of around 180 ml/kg/min, and sled dogs that run the Iditarod
have a V02 max of 240 ml/kg/min. At the other end of the spectrum, a human must have a V02
of 15-20 ml/kg/min to live independently, and a decline of 0.4-0.5
ml/kg/min per year, or 5-10% per decade, is normal after age 50.
Musculature.
Muscular fitness is measured not
only by muscle size and fat concentrations, but also by strength, power, and
endurance. Strength is an easy
concept—how much you can lift or push—and it is measured in pounds or the
equivalent. Power is more complicated
though; expressed in watts, it tells you how much weight you can move in a
given amount of time. And
endurance, of course, refers to how long you can make a particular muscle
perform.
So now, what is the effect of exercise on aging adults? One of the best ways to answer this
question is by studying “masters athletes,” defined as individuals who are over
40 and train for fitness and sports competitions.
A 2011 study* looked at 20 men and 20 women who were (a) over
40 years old, (b) trained for competitions MORE than 4-5 times per week, and (c)
did not have an injury that limited their ability to compete. They were divided into four age groups
with 5 men and 5 women in each group: 40-49 years, 50-59 years, 60-69 years,
and over 70 years. Using the
cross-sectional images of each subject’s upper leg provided by MRI (magnetic
resonance imaging) scans, researchers calculated the amount of fat and muscle in
the thigh as well as the extent to which the fat had penetrated the muscle.
And what did they find? Here are the shockers:
Total mid-thigh mass (muscle
and fat): no difference between age groups.
Lean mass (muscle without
fat): no difference between age groups.
Size of quadriceps (the big
muscle on the top of your thigh):
no difference between age groups except in those over 70, who had a 20%
decrease compared to the other groups.
Physical torque (the amount
of force that can be generated by pushing your leg against resistance): no difference between the 40-49 and the
50-59 age groups and no difference between the 60-69 and the over-70 age
groups, but the 40-59 group exerted more force than the over-60 group.
In summary, no muscular decline was observed until age 60,
and after 60 it did not deteriorate further except for a 20% decrease in
quadriceps size in those over 70.
A 2008 paper that looked at previous studies comparing elite
male athletes with untrained “normal” men concluded that elite athletes can
achieve remarkable performance into their 90’s. For example, knee strength in 90-year-old weightlifters was
higher than that of 40-year-old normal males. The VO2 max of 70-year-old elite runners was
equal to that of untrained 25-year-olds.
The power generated by 75-year-old weightlifters was equal to that of ordinary
25-year-olds.
Now, my purpose in going through these statistics is NOT to suggest
that we can all look like Arnold Schwarzenegger as we slide into our golden
years. Unfortunately, there are
very real events that occur as we age—and the list is depressingly long!
What is known, again by looking at the performance of elite
athletes, is that all of the above measures—strength, power, V02
max—decrease with age. A weight-trained
90-year-old is never going to be able to compete with a weight-trained 20-year-old.
In fact, in all these studies the
trained youngsters outperformed the trained oldsters by great margins in all
age categories. Peak endurance
running, for example, is maintained until approximately 35 years old, with
modest decreases thereafter until 50-60 and larger drop-offs after that. This decline in athletic performance is
well known in all sports.
My intent is to make the point that recent studies reveal
that people of all ages show remarkable improvement with training, and
therefore some aspects of the aging stereotype are simply WRONG. What is going on at the biochemical
level is not yet fully known, but it appears that the capacity for protein
synthesis may remain essentially unchanged as we age. Think about THAT!
So what is the evidence? Looking at masters athletes is useful in many ways—but maybe
there is something different about them other than their capacity for
continuous training. What we
really need to know is how “normal” people respond to training.
But first, a little vocabulary that is used in the exercise
world. “Resistance training”
essentially means lifting weights by any mechanism—a mechanical apparatus (think
Nautilus machines) or free weights (barbells, for example) or “body weight” (such
as pull-ups or push-ups).
Resistance training with free weights or machines is often structured around
percentages of the “one rep
maximum” (1RM), which is the maximum weight that can be lifted or pushed one
time for a given exercise. A “low”
workout could incorporate groups of repetitions (reps) at 60% 1RM, so your
exercise on a given day might consist of three sets of 10 reps at your 60%
1RM. Obviously the possible
variations on this theme are endless.
A 2010 meta-analysis of 47 studies covered 1079 subjects
ranging in age from 50-92 (average age 67) who were subjected to resistance
training. Depending on the parameters of each
individual study, the subjects worked out 1-3 times per week (average 2.7) at 40%-85%
of their 1RM. The number of
exercises ranged from 5 to 16 (average 8.3). The number of sets per exercise ranged
from 1 to 6, (average 2.5) and the number of repetitions per set ranged from 2 to
20 (average 10). The length of the
rest periods between sets varied from 60 seconds to 360 seconds. The
types of exercises performed were leg presses, chest presses, knee extensions,
and “lat” (latissimus dorsi) pull-downs. The studies varied in length from 6 to 52 weeks.
It is clear that some of these studies involved workouts
that were pretty intense by any standard.
And remember, these were folks who were, on average, 67 years old!
So what were the results?
Statistically significant improvements were found across the
board. Strength increased by 29%
for the leg press, 24% for the chest press, 33% for the knee extension, and 25%
for the lat pull-down. And
get this: as the intensity of the
training increased, so did the rate of improvement (an average 5.3% increase in
strength from one level of intensity to the next).
These are huge improvements, especially when you consider
that the test subjects were assumed to be declining in strength because of
“aging.” The good news is that
when their muscles were strained and their tissues torn (which always happens
with resistance training), their bodies recovered and were even better
afterwards. It means protein
synthesis was going on. And
surprisingly, the level of improvement was the same for both men and women in
all age groups (although some studies have found that youngsters gain strength
more rapidly than oldsters).
Clearly these results suggest whole new types of exercise
programs for the elderly, not only modifying exercise intensity but also varying
the exercise program over time—what’s called “periodization.” An exercise program that incorporates “periodization”
would involve, for example, two weeks of high-intensity training followed by a
week at low intensity, followed by high intensity, etc. Periodization has been well-studied in
young athletes, but among the aged not at all. Why? Because, I
guess, they weren’t expected to respond.
Because they are OLD, you know?
The general importance of exercise, even very moderate
exercise, is well known—case closed on that. What these studies show is that for all ages, the more you
exercise the better. And the
harder it is, the more you gain.
The old saying “no pain no gain” apparently applies no matter what your
age (up to a certain point that is, which I’ll discuss in another blog).
Finally, I’d like to share another study supporting the
benefits of exercise—not only cardiovascular fitness but muscular fitness as
well. The two are different, but
certainly related.
From 1980 to 1989, 10,265 men entered the study and were categorized
by age, weight, minimal ability to work out on a treadmill (as a measure of
cardiovascular fitness), and ability to perform leg and chest presses (as a
measure of muscular fitness). By
the end of the study in 2003, 8,762 subjects remained, ranging in age from 20
to 80. Some of them had died
or suffered heart attacks, strokes, cancer, or diabetes, but the average man
was followed for 19 years.
The researchers divided the men into three groups (low,
middle, and high) according to their muscular strength at the time they entered
the study. Basically they found
that the stronger the group, the less mortality there was from any cause,
including cancer and cardiovascular disease. This was true even after controlling for varying initial levels
of cardiovascular health (although greater cardiovascular health was correlated
with higher muscular strength).
This study’s focus on muscular strength makes it different
from many others because the majority have focused on the
health benefits of cardiovascular exercise (running, walking, etc.). It is not known how muscular
strength protects against disease, but some researchers believe that it may be
due to the type of muscle fibers one has.
Given the fact that aging baby boomers constitute 26%
percent of the United States population, these kinds of studies are very
important. The results are
changing the paradigms of aging as well as the vocabulary, as evidenced by the
fact that terms like “successful aging,” “active aging,” “positive aging,” and
“active living” are increasingly in use.
And those of us who are no longer young need to actively
counter stereotypes of aging and the cultural expectations about “what we can
do.”
The Pepsi Generation may be getting old, but we are still a
force to be reckoned with!
Useful References:
https://physsportsmed.org/sites/default/files/rpsm.2011.09.1933_secure.pdf
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