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| Hormonal responses to whole-body
vibration in men. |
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Bosco C, Iacovelli M, Tsarpela O,
Cardinale M, Bonifazi M, Tihanyi J,
Viru M, De Lorenzo A,
Viru A. |
| 2000 |
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| NCBI |
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Societa Stampa Sportiva, Rome, Italy
The aim of this study was to evaluate the acute responses of blood
hormone concentrations and neuromuscular performance following whole-body
vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25
(4.6) years] were exposed to vertical sinusoidal WBV, 10 times for
60 s, with 60 s rest between the vibration sets (a rest period lasting
6 min was allowed after 5 vibration sets). Neuromuscular performance
tests consisting of counter-movement jumps and maximal dynamic leg
presses on a slide machine, performed with an extra load of 160% of
the subjects body mass, and with both legs were administered before
and immediately after the WBV treatment. The average velocity, acceleration,
average force, and power were calculated and the root mean square
electromyogram (EMGrms) were recorded from the vastus lateralis and
rectus femoris muscles simultaneously during the leg-press measurement.
Blood samples were also collected, and plasma concentrations of testosterone
(T), growth hormone (GH) and cortisol (C) were measured. The results
showed a significant increase in the plasma concentration of T and
GH, whereas C levels decreased. An increase in the mechanical power
output of the leg extensor muscles was observed together with a reduction
in EMGrms activity. Neuromuscular efficiency improved, as indicated
by the decrease in the ratio between EMGrms and power. Jumping performance,
which was measured using the counter-movement jump test, was also
enhanced. Thus, it can be argued that the biological mechanism produced
by vibration is similar to the effect produced by explosive power
training (jumping and bouncing). The enhancement of explosive power
could have been induced by an increase in the synchronisation activity
of the motor units, and/or improved co-ordination of the synergistic
muscles and increased inhibition of the antagonists. These results
suggest that WBV treatment leads to acute responses of hormonal profile
and neuromuscular performance. It is therefore likely that the effect
of WBV treatment elicited a biological adaptation that is connected
to a neural potentiation effect, similar to those reported to occur
following resistance and explosive power training. In conclusion,
it is suggested that WBV influences proprioceptive feedback mechanisms
and specific neural components, leading to an improvement of neuromuscular
performance. Moreover, since the hormonal responses, characterised
by an increase in T and GH concentration and a decrease in C concentration,
and the increase in neuromuscular effectiveness were simultaneous
but independent, it is speculated that the two phenomena might have
common underlying mechanisms. |
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