When It Comes To
Stretching, Pain Isn’t A Measure Of Gain
SAN FRANCISCO (April 3, 2006) – If you’re a mouse,
then stretching before you exercise is a good thing – even as long as two
weeks before your next cheese hunt or cat run. But if you’re reading this
for yourself, it’s a bit more complicated.
When most of us think of stretching, we’re imagining at
a minimum jogging, and probably something more like downhill skiing or
sprints. But when University of Michigan researchers Nicole Lockhart and
Susan Brooks talk stretching, their real interest is how to condition older
folks’ muscles so they’ll eventually be willing to do even a little exercise
to garner all the benefits that will follow.
“The elderly are far more susceptible to
contraction-induced injury,” notes Lockhart, lead author in two related
papers being presented in American Physiological Society sessions at
Experimental Biology in San Francisco. “Sometimes just by normal activity or
a sudden movement a leg will jut out too far and they’ll suffer a minor
injury, but they’ll be wary of further damage,” she said.
Protect those muscles, as minor injuries may be
cumulative
Brooks, her adviser, added: “We think that cumulative
muscle injury may contribute to the loss of muscle mass as we grow old. So
protecting muscles at all times is a good thing. And understanding how
stretching increases resistance to injury will really help to do this.”
The team had previously shown that stretching decreased
muscle injury in mice when stretches were performed anywhere from one hour
to 14 days (yes days) prior to exercise. But they didn’t know why. What is
known is that while stretching muscles produce nitric oxide (NO), a common
signaling molecule. NO increases blood flow and decreases force during
submaximal contractions, and also can modulate inflammation.
NO protects without stretching; but without NO,
stretching doesn’t seem to protect
So they tested whether the anti-inflammatory effects of
NO were involved in the protection provided by stretching. And the results
were: mixed. Mice were given substances that either increased or inhibited
NO production. They found that increasing NO reduced inflammation and other
measures of injury following exercise by half – even without prior
stretching. On the other hand, when NO production was restricted, stretching
an hour before exercise didn’t reduce injury at all.
They also tested whether low level inflammation seen
after stretching somehow primes muscles to decrease inflammation following
subsequent damaging exercise. They found that when an antibody was
administered that reduced the inflammation induced by stretching, no
protection following subsequent exercise was observed.
Insights, but not yet answers on mechanisms of
protection
“The results are somewhat contradictory,” Brooks
offers, “because first nitric oxide appeared to be important by inhibiting
inflammation, but our second experiment showed that if you prevent
inflammation you don’t get the protection afforded by stretching.
Nevertheless, while translating animal studies to human athletes, or elderly
humans for that matter, is difficult, these studies do provide important
insights into how different modes of training reduce muscle injury.”
*Paper presentations: “NO is necessary and
sufficient for the protection from contraction-induced injury provided by
passive-stretch-conditioning,” 12:30 p.m.- 3 p.m. Sunday April 2, APS
Physiology Exercise Responses and Training Section 237.19/board #C773.
Research was by Nicole C. Lockhart and Susan V. Brooks,
Department of Physiology and Institute of Gerontology, University of
Michigan, Ann Arbor.
And, “The infiltration of neutrophils following
passive-stretch-conditioning is required for protection from
contraction-induced injury”: 237.20/board #C774.
Funding: National Institute on Aging/NIH.
* * *
Editor’s Note: For
further information or to schedule an interview with a member of
the research team, please contact Donna Krupa at the APS newsroom @
415.905.1024 (March 31-April 5); or (703) 967-2751 (cell) or (301) 634-7209
(office),
dkrupa@the-aps.org; or Christine Guilfoy at 978.290.2400 (cell) or
301.634.7253 (office).
* * *
The
American Physiological Society was founded in 1887 to foster basic and
applied bioscience. The Bethesda, Maryland-based society has more than
10,500 members and publishes 14 peer-reviewed journals containing almost
4,000 articles annually.
APS
provides a wide range of research, educational and career support and
programming to further the contributions of physiology to understanding the
mechanisms of diseased and healthy states. In May 2004, APS received
the Presidential Award for Excellence in Science,
Mathematics and Engineering Mentoring (PAESMEM).
# # #
A searchable
online program for EB is at
http://www.faseb.org/meetings/eb2006/call/default.htm
Experimental Biology is an annual
scientific meeting convened by the Federation of American Societies of
Experimental Biology, including the American Physiological Society (APS)
and other biomedical societies. The meeting features “nominated” lectures,
symposia, research presentations, awards, a job placement center, and an
exhibit of scientific equipment, supplies, and publications. This year’s
participating Societies are APS, American Association of
Anatomists, American Society for Biochemistry and Molecular Biology,
American Society for Investigative Pathology, American Society for
Nutritional Sciences, and the American Society for Pharmacology and
Experimental Therapeutics.
