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JOURNAL
OF
SPORTS SCIENCE &
MEDICINE
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Research
article
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EFFECTS OF PROLONGED TENDON VIBRATION STIMULATION ON ECCENTRIC AND CONCENTRIC MAXIMAL TORQUE AND EMGS OF THE KNEE EXTENSORS |
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Yu Konishi1  ,
Junjiro Kubo2 and Akinori Fukudome1 |
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1Department of Physical Education, National Defence Academy, Kanagawa, Japan, 2Faculty of low, Heisei International University, Saitama, Japan. |
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© Journal of Sports Science and Medicine (2009) 8, 548 - 552 |
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| ABSTRACT | |||
| The purpose of present study was to compare the effect of Ia afferent
attenuation on the activity of alpha motor neuron (MN) during concentric
and eccentric action. Eight male subjects were enrolled in the present study.
The experiments consisted of two sessions of MVC measurements, since all
subjects performed both maximal concentric and eccentric action. EMG signals
were simultaneously measured. To establish the baseline of strength, subjects
were asked to perform MVC of knee extension in each session. After finishing
the measurements, 20 min of vibration stimulation was applied. Immediately
after finishing vibration stimulation, the MVC and AEMG were again measured.
The means of MVC for concentric knee extension at pre and post- vibration
stimulation were 192.2 ± 49.3 Nm and 162.3 ± 47.9 Nm, respectively. The
means of MVC for eccentric knee extension at pre and post-vibration stimulation
were 299.7 ± 77.0 Nm and 247.3 ± 88. 6 Nm, respectively. Two-factor repeated
ANOVA detected significant differences in the MVC. Both main effects for
pre-post condition (F(1,7)=, p = 0.0033) and action (F(1,7)=26.35, p = 0.0013)
were noted. No interaction effect (action x condition) was noted. The means
of AEMG (vastus lateralis (VL), vastus medialis (VM), rectus femoris (RF))
at pre and post -vibration stimulation were decreased. Two-factor repeated
ANOVA detected significant differences in AEMG (VM and VL). Both main effects
for pre-post condition (VL;F(1,7)=7.27, p = 0.0308, VM; F(1,7)=9.55, p =
0.0175) and action (F(1,7)=12.40, p = 0.0097) were noted in the VL and the
VM but not in the RF. Furthermore, significant interaction (action x condition)
effect was noted in the VM (F(1,7)=7.03, p = 0.0328) but not in the VL.
The MVC and the EMG activity of the VL in response to the prolonged vibration
stimulation were significantly reduced in eccentric contraction over concentric
contraction. These results represented that a deactivation effect on the
alpha MN of the VL during eccentric action was greater than that of concentric
action. Key words: Concentric contraction, MVC, Vibration stimulation, QF. |
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