Modulacija refleksa H po hoji na gredi različnih širin : magistrsko delo

Misotič, Nina (author), Tomažin, Katja (mentor)

Cilj magistrske naloge je bil preveriti razlike med tremi zahtevnostmi enake ravnotežne naloge (RN), njihov vpliv na amplitudo refleksa H in ali je modulacija refleksa H povezana z učinkovitostjo izvedbe RN. V eksperimentu je prostovoljno sodelovalo 10 preizkušancev. Vsak je izvedel hojo po gredeh treh različnih širin po naključnem vrstnem redu. Preizkušanci so prehodili eno gred na dan. Odmor med posameznimi prehodi čez različne širine gredi je bil najmanj dva dni. Preizkušanci so izvedli šest prehodov posamezne gredi s prekrižanimi rokami na prsih. Modulacijo spinalnih mehanizmov smo spremljali z merjenjem vala H mišice soleus. Ustrezno osnovno aktivnost m. soleus (bEMG) smo pridobili pred in po (deset sekund, pet minut in deset minut) šestih poskusih na posamezni gredi. Vsi odkloni od normalne hoje so bili smatrani kot neuspešni (sestop, premik rok iz določenega položaja itd.). Pri opaženem neuspehu, se je poskus in merjenje prehojene razdalje ustavilo in začel se je nov poskus. Ugotovili smo, da je prehojena razdalja statistično različna med tremi širinami gredi (p<0,001). Povezanost med osnovno aktivnostjo mišice soleus (bEMG) in modulacijo refleksa H kaže, da posamezniki, pri katerih je normalizirana aktivacija m. soleus v stoji večja, manj modulirajo refleks H pri prehodu iz leže v stojo in obratno (p=0,01, p=0,438, p=0,624), povezanosti med bEMG m. soleus in modulacijo refleksa H po prehodu vseh širin gredi pa nismo ugotovili. Čeprav modulacija refleksa H mišice soleus ni bila ugotovljena po prehodih vseh širin gredi, je bila amplituda refleksa H značilno nižja po prehodih ozke gredi v primerjavi s široko (Po; p<0,001; Po 5; p<0,01; Po 10; p<0,05). Analiza povezanosti je pokazala, da so preizkušanci, ki so bolj znižali amplitudo refleksa H pri prehodu iz leže v stojo, prehodili daljšo razdaljo po ozki gredi (p=0,038). Prav tako se nakazuje, da posamezniki, ki prehodijo daljšo razdaljo po ozki gredi, bolj znižajo amplitudo refleksa H po prehodih le-te (p=0,080). Zato ugotavljamo, da je modulacija refleksa H pomemben pokazatelj dinamičnih ravnotežnih sposobnosti. Rezultati naše študije kažejo, da je sposobnost znižanja spinalne vzdražnosti en izmen glavnih mehanizmov, ki vplivajo na naloge statičnega in dinamičnega ravnotežja, najverjetneje zaradi povečane predsinaptične inhibicije Ia aferentnih vlaken.

• Language: Slovenian
• Keywords: ravnotežje, refleks H, hoja, zahtevnost, vzdražnost
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FŠ - Faculty of Sport
• Year: 2017
• PID: 20.500.12556/RUL-92279
• COBISS.SI-ID: 5126833
• Publication date in RUL: 13.05.2017

Secondary language

• Language: English
• Title: Modulation of H-reflex in beam walking of varying widths

Abstract

The purpose of this study was to determine differences between three different difficulties of the same balance task, their influence on H-reflex amplitude and to find out if there is a conection in modulation of H-reflex amplitude and proficiency of balance task. The research included 10 voluntary participants. Each of them performed walking over of three different beam widths in random order. Participants walked across one beam per day. The rest period between walking over different beam width was at least two days. Participants performed six walking trials across the same width with their arms crossed over their chest. Modulation of spinal mechanisms was evaluated with soleus H-reflex. Corresponding background EMG of soleus muscle was obtained before and after (ten seconds, five minutes and ten minutes) six trials of each beam. Anything else except normal walking was considered a balance failure (stepping off, moving arms from a fixed position, etc.). Once a balance failure was observed during a trial, that trial and the collection of walking distance were stopped and the next trial started. Walking distance was statistically different between three different beam width (p<0,001). Correlation between background EMG of soleus muscle (bEMG) and H-reflex modulation shows that individuals with bigger normalized activation when standing, modulated H-reflex less from prone to standing and vice versa (p=0,01, p=0,438, p=0,624). But there was no correlation between bEMG m. soleus and H-reflex modulation following walking across all beam widths. Although modulation of H-reflex from soleus muscle was not observed following walking ascross all beam widths, H-reflex amplitude was significantly lower following narrow beam compared to wide beam (Po; p<0,001; Po 5; p<0,01; Po 10; p<0,05). Analysis of correlation showed that participants, whose H-reflex modulation decreased from prone to closed-legged standing, walked greater distance on narrow beam (p=0,038). There is also a tendency that participants that walked a greater distance across narrow beam, showed a greater decrease in H-reflex amplitude after walking on narrow beam (p=0,080). Therefore, we suggest that regulation of H-reflex could be a reliable measure of dynamic balance abilities. Thus, the results of our study imply that the ability to down regulate the spinal excitability is one of the main mechanisms, which influence the static and dynamic balance tasks probably due to increased presynaptic inhibition of Ia afferents.

• Keywords: balance, reflex H, walk, intensity, exitability