학술논문
Pozadinski mehanizmi bilateralnoga deficita jakosti i snage pri izvedbi vertikalnoga skoka: živčana inhibicija nasuprot odnosa sile i brzine ekstenzora nogu
Underlying mechanisms of the bilateral strength and power deficit during vertical jumping: neural inhibition versus force-velocity characteristics of the leg extensor muscles
Underlying mechanisms of the bilateral strength and power deficit during vertical jumping: neural inhibition versus force-velocity characteristics of the leg extensor muscles
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TEXT
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Source
Subject
Language
Croatian
Abstract
Bilateralni deficit (BLD) fenomen je koji dovodi do smanjenja motoričkog izlaza ekstremiteta prilikom izvedbe bilateralnog motoričkog zadatka u odnosu na motorički izlaz pri izvedbi zadatka unilateralno. Ne postoji jasno utvrđen mehanizam koji se nalazi u pozadini ovog fenomena, posebice u vertikalnim skokovima (VS). Dva mehanizma koja se spominju u VS-u jesu živčana inhibicija u bilateralnim kontrakcijama i promjena u odnosu sila-brzina ekstenzora nogu. Cilj ovog istraživanja bio je utvrditi je li bilateralni deficit (BLD) jakosti i snage u VS-u primarno posljedica: (1) živčane inhibicije u bilateralnim kontrakcijama ili (2) promjene u odnosu sila-brzina ekstenzora nogu. Rezultati ukazuju na postojanje BLD-a jakosti i snage. Prilikom izvedbe VS-a s vlastitom tjelesnom masom, BLD kod mehaničkog izlaza relativne prosječne sile iznosio je 37 %, dok je veličina BLD-a relativne prosječne snage iznosila 10 %. Kod relativnog obavljenog rada zabilježen je BLD od gotovo 31 %. Glavni nalaz pokazuje značajan utjecaj rasterećenja na veličinu BLD-a kod relativne prosječne sile. Također je utvrđen značajan utjecaj rasterećenja na mehanički izlaz sile i snage, kao i na obavljeni rad. Rezultati EMG aktivnosti mišića ukazuju na simultano opadanje mehaničkog izlaza sile i EMG aktivnosti mišića. Osim utvrđenog bilateralnog EMG deficita, u nekim mišićima utvrđena je i bilateralna EMG facilitacija. Ovo je istraživanje ukazalo na neuromehaničko izvorište fenomena BLD-a jakosti pri izvedbi prirodnih balističkih pokreta kao što je VS te je unaprijedilo razumijevanje živčano-mišićne funkcije čovjeka. S obzirom na dobivene rezultate utvrđen je naglašeni utjecaj karakteristika odnosa sila-brzina na fenomen BLD-a jakosti. Time je potvrđeno kako je u prirodnim VS-ovima važan mehanizam u pozadini BLD-a jakosti promjena odnosa sila-brzina u unilateralnim naspram bilateralnih skokova. To međutim ne znači da živčana inhibicija nije mehanizam u pozadini BLD-a jakosti. Bilateralni EMG deficit, a negdje i bilateralna EMG facilitacija zabilježena kod VS-a ukazuje da živčani čimbenici zasigurno utječu na BLD kod mehaničkog izlaza sile u VS-u. Sveukupno gledajući, dobiveni rezultati ukazuju na utjecaj biomehaničkih i živčanih faktora na nastanak fenomena BLD-a jakosti i snage u vertikalnim skokovima.
Bilateral deficit (BLD) is a phenomenon that leads to decrease of motor output from one limb in motor task that is performed bilaterally when compared with motor output from the same limb in motor task that is performed unilaterally. There is no clearly defined mechanism that lies behind this phenomenon. Previous research suggested two mechanisms in vertical jumping (VJ); neural inhibition in bilateral contractions and change of force-velocity relationship in leg extensor muscles. The purpose of this research was to determine whether the reason of BLD in force during VJ is neural inhibition in bilateral contractions or a change in force-velocity relationship in leg extensor muscles. Results are indicating occurrence of BLD in mechanical output of relative average force and power, but also in the relative work. In the performance od VJ with subject’s own body mass BLD in relative average force was 37%, while the size of BLD in power was 10%. BLD in work was 31%. Main findings show significant impact of unloading on the size of BLD in relative average force. There was also a significant influence of unloading on mechanical output of force, power and work. Results of EMG activity showed simultaneous decreas of muscle activity and mechanical force output. While bilateral EMG deficit was found in the most of muscles, there was also a bilateral EMG facilitation found in some muscles. This research has indicated neuro-mechanical source of bilateral force deficit phenomenon in ballistic motor task like VJ, and it has improved our understanding of human neuromuscular function. Regarding the results of this research, there has been found a significant influence of the force-velocity properties of the muscles on the occurrence of BLD phenomenon in mechanical force output. It has been also confirmed that in the natural tasks like VJ a significant mechanism behind aforementioned phenomenon is change in forcevelocity relationship between unilateral and bilateral performance of VJ. This conclusion does not discard influence of neural factors in the occurrence of investigated phenomenon. Bilateral EMG deficit and in some cases, bilateral EMG facilitation in VJ performance clearly shows the effect of neural factors on BLD in mechanical output of force. Altogether, the given results show two segmental BLD and divided role of biomechanical and neural factors behind the occurrence of bilateral force deficit.
Bilateral deficit (BLD) is a phenomenon that leads to decrease of motor output from one limb in motor task that is performed bilaterally when compared with motor output from the same limb in motor task that is performed unilaterally. There is no clearly defined mechanism that lies behind this phenomenon. Previous research suggested two mechanisms in vertical jumping (VJ); neural inhibition in bilateral contractions and change of force-velocity relationship in leg extensor muscles. The purpose of this research was to determine whether the reason of BLD in force during VJ is neural inhibition in bilateral contractions or a change in force-velocity relationship in leg extensor muscles. Results are indicating occurrence of BLD in mechanical output of relative average force and power, but also in the relative work. In the performance od VJ with subject’s own body mass BLD in relative average force was 37%, while the size of BLD in power was 10%. BLD in work was 31%. Main findings show significant impact of unloading on the size of BLD in relative average force. There was also a significant influence of unloading on mechanical output of force, power and work. Results of EMG activity showed simultaneous decreas of muscle activity and mechanical force output. While bilateral EMG deficit was found in the most of muscles, there was also a bilateral EMG facilitation found in some muscles. This research has indicated neuro-mechanical source of bilateral force deficit phenomenon in ballistic motor task like VJ, and it has improved our understanding of human neuromuscular function. Regarding the results of this research, there has been found a significant influence of the force-velocity properties of the muscles on the occurrence of BLD phenomenon in mechanical force output. It has been also confirmed that in the natural tasks like VJ a significant mechanism behind aforementioned phenomenon is change in forcevelocity relationship between unilateral and bilateral performance of VJ. This conclusion does not discard influence of neural factors in the occurrence of investigated phenomenon. Bilateral EMG deficit and in some cases, bilateral EMG facilitation in VJ performance clearly shows the effect of neural factors on BLD in mechanical output of force. Altogether, the given results show two segmental BLD and divided role of biomechanical and neural factors behind the occurrence of bilateral force deficit.