Women are more prone to knee injuries than
men, and the findings of a new study suggest this may involve more than just
differences in muscular and skeletal structure – it shows that males and
females also differ in the way they transmit the nerve impulses that control
muscle force.
Scientists
at Oregon State University found that men control nerve impulses similar
to individuals trained for explosive muscle usage – like those of a sprinter –
while the nerve impulses of women are
more similar to those of an endurance-trained athlete, like a distance runner.
In
particular, the research may help to explain why women tend to suffer ruptures
more often than men in the anterior cruciate ligament of their knees during
non-contact activities. These ACL injuries are fairly common, can be
debilitating, and even when repaired can lead to osteoarthritis later in life.
More
study of these differences in nervous system processing
may lead to improved types of training that individuals could use to help
address this issue, scientists said.
"It's
clear that women move differently than men, but it's not as obvious why that
is," said Sam Johnson, a clinical assistant professor in the OSU School of
Biological and Population Health Sciences.
"There
are some muscular and skeletal differences between men and women, but that
doesn't explain differences in injury rates as much as you might think,"
Johnson said. "No one has really studied the role of the nervous system
the way we have in explaining these differences, specifically the way sensory
information is processed and integrated with motor function in the spinal
cord."
In this
study, just published in the European Journal of Applied Physiology,
the scientists found that most aspects of spinal motor control and rapid
activation of muscles were similar in 17 men and 17 women that were examined –
with one exception. Men had a higher level of "recurrent inhibition,"
which is a process in the spinal cord that helps select the appropriate muscle
response.
Even a
process as simple as walking is surprisingly complicated, as people process
large amounts of information and use varying forces to move around obstacles,
change direction or simply climb up a step.
And
when you slip on an icy patch, the need for extremely rapid and accurate muscle
response might be all that stands between you and a broken hip.
For
some reason, women tend to have knee motions that make them more susceptible to
injury. Among other things, when landing from a jump their knees tend to
collapse inward more than that of most men.
They
suffer significantly more ACL injuries during physical activity.
"We're
finding differences in nervous system processing that we believe are related to
this," Johnson said. "The causes for those differences are unclear,
but it may be due either to a biological difference, such as hormones, or a
cultural difference such as different exercise and training patterns."
This
research was supported by the National Athletic Trainers' Association Research
and Education Foundation. Researchers at Marquette University collaborated on
the work.
While
researchers continue to study what might help address this, Johnson said it's
already possible for women to be more aware of these common differences and do
exercises that should reduce problems.
Many
ACL injury prevention programs incorporate strength, balance, flexibility, and
jump training. However, based on these and other findings, women – especially athletes
– should consider training with motions more similar to those of their sport,
such as squatting, lunging, jumping or cutting side-to-side.
Use of
heavy weights may not really be necessary, Johnson said, so much as mimicking
the motions that often cause this injury.
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