Abstract

The aim of the research was to determine knee extensors force output dependence an oscillation stability fluctuation at different body temperatures. Methods of the study: The object of the study were healthy men who are active physically (n = 10) (age – 21.6 ± 2.6 years old, weight – 81.1 ± 9.9 kg, height – 183.2 ± 7.7 cm). Three tests were carried out. One was control, the other two were experimental. The experimental test differed from the control one in a passive warming (the subjects legs were immersed in a warm water-bath for 45 minutes; the temperature of the water was -44 ± 1°C) and cooling (the subjects’ legs were immersed in a water-bath at the temperature of 15 ± 1°C (this was done twice for 15 min with an interval of 10 min)). The load of maximum voluntary contraction (MVC – 2 min) lasted for 120 seconds, when stretching one of their legs by a knee joint at a 60° fixed angle (isokinetic dynamometer, Biodex), every 15 seconds the muscle was stimulated by electrical impulses the duration of the stimulation was 250 ms, the frequency was 100 Hz, and the voltage was 85-105 V. We registered the moment of MVC (N, m) and the degree of voluntary activation of muscles (VA%). In order to evaluate the muscle isometric force output oscillation stability fluctuation sample entropy were measured. Results and discussion: After passive warming rectal temperature increased from 37.35 ± 0.32 to 39.31 0.31 °C (p < 0.001) and cooling – 37.25 ± 0.38 to 37.15 ± 0.5 °C (p > 0.05). At the end of the load at all test MVC and sample entropy value decreased significantly (p < 0.05). whenever voluntary activation level decreased only in control and passive warming test, comparing to initial. A significant difference of MVC and VA % between the control and passive warming, passive cooling and warming test (p < 0.05), at sample entropy case – between passive cooling and warming test (p < 0.05). During the recovery time, 5 min after the application of the load MVC and VA % recovered to initial in all tests (p > 0.05). Main conclusion: The results showed that the passive warming increased the fatigue of MVC level of VA % and index of sample entropy, whenever passive cooling conversely, reduced the fatigue of MVC, level of VA% and index of sample entropy. Verf.-Referat