Evaluation of muscle mechanical characteristics of legs and arms under different levels of effort

Procena mehaničkih karakteristika mišića kao što su sila (F), brzina (V) i snaga (P) su od velikog značaja za razumevanje funkcije i građe lokomotornog aparata. Opšte je poznato da laboratorijski i terenski testovi koji se koriste za procenu mehaničkih karakteristika mišića (MKM) najčešće zahtevaju maksimalno voljno naprezanje (MVN) kako bi rezultati bili validni i pouzdani. Međutim, postavlja se pitanje kako se menjaju rezultati različitih motoričkih testova ukoliko ispitanik iz voljnih ili nevoljnih razloga ne može ili ne sme da ispolji MVN? Uticaj umanjenog napora na ispoljavanje MVN je neminovan, međutim njegovi efekti na procenjivane MKM, kao i mogućnost upotrebe dobijenih rezultata iz različitih motoričkih zadataka, još uvek nisu dovoljno poznati. Predmet ove disertacije je uticaj umanjenog napora na mehaničke karakteristike mišića. Cilj disertacije je bio da se istraže efekti umanjenog napora na mehaničke karakteristike mišića nogu i ruku pri različitim nivoima opterećenja. U skladu sa predmetom istraživanja, planirana su i sprovedena dva eksperimenta. Eksperiment 1 – Procena mehaničkih karakteristika mišića nogu pri različitim nivoima napora Test vertikalni skok u sportu i sportskoj medicini je opšte prihvaćen i veoma rasprostranjen. Međutim, i dalje nije poznato kako voljno umanjen napor utiče na rezultate testa skoka iz polu-čučnja (SJ). Cilj ove studije je bio da istraži uticaj umanjenog napora na MKM nogu dobijene iz SJ testa pri različitim opterećenjima. Dvanaest ispitanika muškog pola, studenata Fakulteta sporta i fizičkog vaspitanja (21.1 ± 1.1 godina) je izvodilo SJ test po 2 pokušaja pri 3 nivoa napora (100%, 75% i 50% od maksimalnog napora) i 4 nivoa opterećenja (0, 20, 40 i 60 % 1-RM čučnja). Podaci brzine (VN), sile (FN) i snage (PN) mišića nogu dobijeni su obradom podataka sa platformi sile. Rezultati pokazuju da se sve tri apsolutno izvedene MKM značajno smanjuju pod uticajem umanjenog napora (p < .01) na svakom nivou opterećenja, sa najvišom razlikom između 100% i 50% napora (p < .001). Međutim, značajne i velike razlike između opterećenja su pronađeni u VN i FN (p .1). Takođe, značajne i velike razlike su pronađene i u relativnom padu napora između PN sa VN (p < .01) i FN (p < .01). Relativni pad u PN pri naporu od 75% usrednjen kroz sva opterećenja je bio u proseku 34,1 ± 6.2 (p < .01), i pri naporu od 50% je bio 38.1 ± 4% (p < .01). Dobijeni rezultati ukazuju da ispoljena snaga najbolje opisuje efekte voljno umanjenog napora u SJ testu. Takođe, s obzirom da nema interakcija između napora i opterećenja u relativnom padu snage rezultati se uklapaju u teoriju da motorne komande upravljaju osećajem napora nezavisno od osećaja težine i mišićne tenzije. Ovi rezultati su od značaja za upotrebu SJ testa u kliničke svrhe, sugerišući da se snaga nogu može koristiti za opis neuromišićnih kapaciteta u uslovima kada ispitanik ne sme ili ne može da ispolji maksimalno voljno naprezanje...Assessing of muscle mechanical characteristics such as force (F), velocity (V) and power (P) are of essential importance for understanding the function and structure of human locomotor system. It is generally known that laboratory and field tests used to assess the muscle mechanical characteristics (MMC) most often require maximum voluntary exertion to produce valid and reliable results. However, the question that arises is how a results of various motor tests change if the subject due to some voluntary or unvoluntary reasons cannot or must not generate maximum exertion? However, the effects of submaximal effort on the manifestation of maximum voluntary exertion are inevitable, but it is still unknown what MMC are the most sensible under voluntary reduced effort in various motor tasks. The subject of this dissertation is the influence of reduced effort on the mechanical characteristics of muscles. The aim of this dissertation was to investigate the effects of voluntary reduced effort on the mechanical characteristics of the leg and arm muscles at different levels of external load. In accordance with the subject of the dissertation, two experiments were planned and conducted. Experiment 1 - Evaluation of mechanical characteristics of leg muscles at different levels of effort The vertical jump test is generally accepted and very widespread in sports and clinical testing. However, it is still not known how the voluntarily reduced effort affects the results of the squat jump test (SJ). The aim of this study was to investigate the effect of reduced effort on the MMC of legs obtained from the SJ test under different load conditions. Twelve male students of the Faculty of Sports and Physical Education (21.1 ± 1.1 years) have performed SJ test 2 times at 3 levels of effort (100%, 75% and 50% of maximum effort) and 4 levels of load (0, 20, 40 and 60% 1-RM). Velocity (V), force (F) and power (P) of leg muscles were recorded with force platform. The results show that all three absolute leg MMC variables decreased significantly under the influence of reduced effort (p < .01) at each load level, with the highest important difference found between 100% and 50% of voluntary effort (p < .001). Differences between loads were found for V and F (p .1). Also, differences were found within relative fall of effort between P with V (p < .01) and F (p < .01). The relative fall of P at 75% of effort was in average 34.1 ± 6.2% (p < .01), and at 50% of effort was 38.1 ± 4% (p < .01). These results show that power could describe the best effects of voluntary reduce effort in SJ test. Also, since there was no interaction between effort and load within relative fall of P, the results are supporting the theory that motor commands control the perception of effort independently of the perception of weight and muscle tension..