Date: December 5, 2011
URL: http://www.healthcanal.com/bones-muscles/24127-How-muscle-fatigue-originates-the-head.html
How muscle fatigue originates in the head
-----------------------------------------
Researchers from the University of Zurich have now studied in detail
what sportsmen and women know from experience: The head plays a key
role in tiring endurance performances.
They have discovered a mechanism in the brain that triggers a
reduction in muscle performance during tiring activities and ensures
that one's own physiological limits are not exceeded. For the first
time, the study demonstrates empirically that muscle fatigue and
changes in the interaction between neuronal structures are linked.
The extent to which we are able to activate our muscles voluntarily
depends on motivation and will power or the physical condition and
level of fatigue of the muscles, for instance. The latter particularly
leads to noticeable and measurable performance impairments. For a long
time, the research on muscle fatigue was largely confined to changes
in the muscle itself. Now, a joint research project between the
University of Zurich and ETH Zurich has shifted the focus to brain
research. Headed by neuro-psychologist Kai Lutz from the University of
Zurich in collaboration with Urs Boutellier from the Institute of
Human Movement Sciences and Sport at ETH Zurich, the researchers
discovered neuronal processes for the first time that are responsible
for reducing muscle activity during muscle-fatiguing exercise. The
third and final part of this series of experiments, which was
conducted by Lea Hilty as part of her doctoral thesis, has now been
published in the 'European Journal of Neuroscience'.
Muscle's nerve impulses inhibit motoric area in the brain
In the initial study, the researchers showed that nerve impulses from
the muscle - much like pain information - inhibit the primary motoric
area during a tiring, energy-demanding exercise. They were able to
prove this using measurements in which study participants repeated
thigh contractions until they could no longer attain the force
required. If the same exercise was conducted under narcotization of
the spinal chord (spinal anesthesia), thus interrupting the response
from the muscle to the primary motoric area, the corresponding
fatigue-related inhibition processes became significantly weaker than
when the muscle information was intact.
In a second step, using functional magnetic resonance imaging, the
researchers were able to localize the brain regions that exhibit an
increase in activity shortly before the interruption of a tiring,
energy-demanding activity and are thus involved in signalizing the
interruption: the thalamus and the insular cortex - both areas which
analyze information that indicates a threat to the organism, such as
pain or hunger.
Neuronal system has regulating effect on muscle performance
The third study has now shown that the inhibitory influences on
motoric activity are actually mediated via the insular cortex: In
tests using a bicycle ergometer, the researchers determined that the
communication between the insular cortex and the primary motoric area
became more intensive as the fatigue progressed. 'This can be regarded
as evidence that the neuronal system found not only informs the brain,
but also actually has a regulating effect on motoric activity,' says
Lea Hilty, summing up the current result. And Kai Lutz points to the
new research field that now opens up with these results: 'The findings
are an important step in discovering the role the brain plays in
muscle fatigue. Based on these studies, it won't just be possible to
develop strategies to optimize muscular performance, but also
specifically investigate reasons for reduced muscular performance in
various diseases.' Prolonged reduced physical performance is a symptom
that is frequently observed in daily clinical practice. It can also
appear as a side effect of certain medication. However, so-called
chronic fatigue syndrome is often diagnosed without any apparent cause.
Literature:
Lea Hilty, Lutz Jancke, Roger Luechinger, Urs Boutellier, and Kai
Lutz. Limitation of Physical Performance in a Muscle Fatiguing
Handgrip Exercise Is Mediated by Thalamo-Insular Activity. Human Brain
Mapping. December 10, 2010. doi: 10.1002/hbm.21177
Lea Hilty, Kai Lutz, Konrad Maurer, Tobias Rodenkirch, Christina M.
Spengler, Urs Boutellier, Lutz Jancke, and Markus Amann. Spinal opioid
receptor-sensitive muscle afferents contribute to the fatigue-induced
increase in intracortical inhibition in healthy humans. Experimental
Physiology. February 11, 2011. doi: 10.1113/expphysiol.2010.056226
Lea Hilty, Nicolas Langer, Roberto Pascual-Marqui, Urs Boutellier, and
Kai Lutz. Fatigue-induced increase in intracortical communication
between mid ?anterior insular and motor cortex during cycling
exercise. European Journal of Neuroscience. November 21, 2011. doi:
10.1111/j.1460-9568.2011.07909.x
--------
(c) 2011 HealthCanal
---------------------------------------------
Send posts to CO-CURE@listserv.nodak.edu
Unsubscribe at http://www.co-cure.org/unsub.htm
---------------------------------------------
Co-Cure's purpose is to provide information from across the spectrum of
opinion concerning medical, research and political aspects of ME/CFS and/or
FMS. We take no position on the validity of any specific scientific or
political opinion expressed in Co-Cure posts, and we urge readers to
research the various opinions available before assuming any one
interpretation is definitive. The Co-Cure website <www.co-cure.org> has a
link to our complete archive of posts as well as articles of central
importance to the issues of our community.
---------------------------------------------
