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purpose of this study was to evaluate contractile properties of the
tibialis anterior of paralyzed and non-paralyzed subjects. The contractile
properties and the fatigability of the tibialis anterior muscle (TA)
were tested in 8 spinal cord injured (SCI) and 8 control individuals.
The TA was stimulated at frequencies from 10 to 100 Hz to determine
a force-frequency curve. A fatigue bout was also performed by stimulating
the muscle at 40 Hz every two seconds for three minutes. The SCI muscles
produced lower forces overall, but higher forces relative to maximal
force at lower frequencies, shifting the force-frequency curve of
the SCI group to the left. The half-relaxation time and rate of relaxation
at 40 Hz was slower in the SCI muscles than in the control muscles
(127 ± 18.4 ms vs. 78 ± 8.7 ms, 6 ± 1.5 kg·s-1 20 ± 4.1
kg·s-1 respectively). In addition, force loss and slowing
of relaxation during the fatigue protocol were not significantly different
between the two groups due to high variability in the SCI group. The
TA of the SCI group had slower contractile properties than the control
group and fatigability was not significantly different between the
SCI and control group. The protocol may be useful to assess training
effects during rehabilitation of paralyzed muscle.
KEY
WORDS: Muscle, contractility, fatigue, paralysis, paraplegia.
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