Learning
from the horses...Exercise helps
protect muscles in elderly from
soreness, injury
Newswise
Researchers now have the physical evidence to show why it's
important for older people to exercise. And it comes with the
discovery that, in aging racehorses, regular aerobic workouts
decreased the prevalence of muscle damage that can be caused by
exertion.
Mammalian skeletal muscle tissue
is the same regardless of which species of mammal it is in, said
Steven Devor, the study's lead author and an assistant professor of
exercise science education at Ohio State University.
He and his colleagues studied the
effects of aerobic exercise in this case, galloping on a treadmill
on small sections of skeletal muscle tissue taken from the limbs
of retired racehorses. The findings support a use-it-or-lose-it
philosophy: After 10 weeks of regular workouts, the horses' muscles
showed fewer signs of damage caused by exertion, even after the
horses worked out at their maximum capacity.
The results apply to humans and
are especially important for older adults, Devor said.
"We have to work at keeping muscle
mass as we age, otherwise that mass wastes away," he said. "This
weakness leaves a muscle more prone to injury even when it's the
least bit exerted. Also, joints are less likely to break if the
musculature surrounding them is strong."
"According to these results,
aerobic exercise training improves the ability of aging skeletal
tissue to resist injury," Devor said.
He and his colleagues report their
findings in a recent issue of the Journal of Applied Physiology.
Some minor muscle damage is normal
after a new or a particularly difficult workout. The pain that often
appears a day or two after such exertion is called delayed onset
muscle soreness, or DOMS.
"The way to get rid of this kind
of pain is to stay physically active," Devor said. "It's ironic, but
muscles are most often injured during exercise. But muscles get
stronger by repairing this damage."
The current study builds on
experiments Devor previously conducted in rats about 10 years ago,
he helped identify the mechanism that causes DOMS.
He was part of a team that found
that this damage happens when tiny skeletal muscle segments called
sarcomeres the smallest units of contractile muscle pull apart
as a muscle lengthens.
Contractions that lengthen muscles
are particularly damaging to sarcomeres. And lengthening
contractions are some of the most common type of contractions humans
do leg muscles contract and lengthen as we sit down or walk and
run, and arm muscles contract and lengthen when we lower heavy
objects.
The six quarter horses in the
current study ranged in age from 23 to 30 years, which made the
animals elderly by horse standards. A horse usually lives for about
28 to 32 years. The animals used a treadmill a long conveyor belt
built into the floor of a barn three times a week for 10 weeks.
Each workout lasted about 20 minutes. The horses got little to no
exercise during the three months leading up to the study that way,
the animals would have nearly the same fitness level once the study
began.
The researchers increased the
speed and resistance of the treadmill during each session, and the
animals spent about 15 minutes of each workout exercising at a
relatively high intensity. Training protocols were updated every two
weeks, based on the animal's performance and its response to the
given workload.
The researchers examined muscle
tissue taken from each horse's forelimb (triceps brachii) and
hindlimb (semimembranosus a large muscle of the thigh, and also
the largest muscle the researchers looked at.) Both muscles are used
during walking and galloping. The researchers also removed a small
piece of the masseter, a muscle that helps the jaw close during
chewing. The masseter served as the control.
The researchers removed small
portions of tissue from each muscle before and immediately after the
first and last treadmill sessions, and also before and after a
session during the eighth week of training.
The treadmill was set at the same
speed and resistance during that eighth-week workout as it was
during the very first workout, in spite of increases in speed and
resistance in the weeks between the two sessions. The researchers
wanted to see if nearly two months of exercising would better
protect the muscles from damage. During the very last workout, the
horses ran at their maximum capacity until they reached exhaustion.
Eight weeks of exercise had a
considerable effect on the hindlimb muscle, as the degree of muscle
damage had decreased three-fold by then. After the first workout,
the researchers noted a five-fold increase in damaged sarcomeres
compared to the muscle tissue they examined prior to the workout.
"It wasn't serious damage, but the
horses probably felt a little sore afterward," Devor said. "A human
would definitely notice some soreness if they hadn't been regularly
exercising."
After the workout during week
eight, researchers measured only a two-fold increase in the
prevalence of sarcomere damage in the hindlimb muscle. They saw the
same results two weeks later, after the very last treadmill session.
"The muscle had become more
resistant to injury by week eight," Devor said. "And it was
stronger, too, since the horses worked as hard as they could during
the very last treadmill session."
The triceps, however, showed about
the same amount of sarcomere damage about two-and-a-half times
more damage before and after each of the workouts.
"The bigger muscle responded in a
positive way to several weeks' worth of conditioning," Devor said.
"It suggests that the protective effect of aerobic training may
benefit larger muscles more than smaller ones.
"It also suggests that there was
less post-exercise pain after the later workouts," he said, adding
that the horses could run up to 24 percent longer by the end of the
study.
As expected, the masseter, or jaw
muscle, was unaffected by the workouts.
"The bottom line is that since the
horses had kept up with their training program, there were dramatic
reductions in the amount of muscle tissue injuries the animals had
by the end of the study," Devor said.
"This suggests that, in older
adults, regular exercise may help prevent injuries associated with
age-related impairments such as reduced muscle strength, impaired
mobility and a tendency to fall."
Devor conducted the study with
Ohio State colleagues Kenneth Hinchcliff, Mamoru Yamaguchi and
Laurie Beard, all with the college of veterinary medicine, and Chad
Markert, formerly with Ohio State's sport and exercise science
program. The work was a portion of the doctoral dissertation of
Jeong-su Kim, who is presently at the University of Alabama,
Birmingham.
The study was supported by the
Equine Research Fund from the College of Veterinary Medicine's
Council for Research at Ohio State.
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