BEIJING, March 21 (Xinhuanet) -- Before old muscles
can spring into action, your neurons have to shout at them, according to a
new study that also reveals exercise could reverse the aging effect.
Researchers examined neuron activity and
corresponding muscle force for 23 subjects between the ages of 18 and 88. They
discovered a diminished ability of the muscles to respond to the commands of
neurons amongst the older participants.
What the researchers studied was the dorsal
interosseous muscle between the index finger and thumb. This muscle is
activated by 120 individual neurons. Each subject had a small needle-like
electrode inserted into their index finger. The electrode was linked to a
computer that recorded the electrical impulses as they traveled from the neurons
to the muscle fibers.
The participants were asked to use that finger to
follow the outline of a wavy line with peaks and valleys on a computer
screen.
"More force -- which this indicated by a
corresponding higher firing rate of neurons -- is exerted just before you begin
the upturn toward one peak and then it eases off again in the downturn toward a
valley," said Christopher Knight, a researcher from the University of
Delaware.
The tests revealed neuron firing rates and muscle
responsiveness were lower in older participants than the younger subjects.
"The repeated contraction of muscles is essential to
movements such as walking," Knight said. "However, our muscles have a reduced
capacity to contract or 'twitch' as we grow older. We lose fast-twitch muscle
fibers as we age."
Knight said this type of reduced neuron activity
could be improved by exercising.
"After power training with weights, we see an
increase in firing rates," Knight said. "For safety, we're commonly advised to
do things slowly when exercising, but it's important to also do some fast
exercises. You need a fast movement to prevent a fall. Even in the frail
elderly, it is possible to use exercise bands for manual resistance to improve
the speed of movement."
(Agencies)
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