The impact of the organism acclimation to hyperthermia on the muscular activity

Firstly, it is important to emphasize that the research of different scientific articles and other sources of information has proved that the increment of temperature in the man’s body as well as the inner muscle causes many physiologic reflexes in human’s organism. However not many research projects analyzing the impact of the acclimation (In vitro(in laboratory) related long term acclimatization) to hyperthermic environment, created in imitative way, neither on the fluctuation of man’s vital functions nor on the maximum voluntary muscle strength, could be found. Secondly, it should be noted, that none of the above mentioned sources provided the information on the change of muscle electric activity at the moment of its maximum voluntary strength. Therefore, the main purpose of this research was to establish and measure the influence of the imitative acclimation of hyperthermia on the man’s body. The main tasks of the project were to observe and evaluate the change of man’s physiological functions (rectal, skin and body temperature, physiologic stress, weight loss, heart rate and thermic stress) during the acclimation to hyperthermia process: before passive heating, during the heating time and after it; to establish the impact of acclimation to hyperthermia on the maximum voluntary force as well as on the maximum activation rate; to establish and measure the impact of the acclimation to hyperthermia on the muscle electrical activity. In order to achieve the desired results and to make useful conclusions eight tests were carried out: one control test and other seven – experimental. As distinct from the control test, the experimental ones included the passive heating of legs (the subjects’ legs were immersed in a warm water-bath for 45 minutes; the water temperature was — 44 ± 1o C). The maximum load of voluntary contraction force (MVC – 2 min) lasted for 120 seconds, when stretching one of their legs by a knee joint at a 60o fixed angle (isokinetic dynamometer, Biodex), every 15 seconds the muscle was stimulated by electric impulses — the duration of the stimulation was 250 ms, the frequency was 100 Hz, and the voltage was 85—105 V. The moment of MVC (N*m), the degree of central activation ratio of muscles (CAR %) and electric activity of muscles were registered (RMS). Conclusions: 1. Seven times on alternate days the passive heating of subjects’ legs which were immersed in a warm-bath for 45 minutes (the water temperature was 44 ± 1oC), applying MVC―2 of intensity, method was used. It revealed that the man’s body acclimation to hyperthermia significantly decreases man’s rectal and body temperature, the physiological index of stress, heart rate and the index of heat stress, while the weight loss if to compared to the body weight, increases 2. The man’s body acclimation to hyperthermia didn’t raise the muscle resistance to fatigue, while applying the MVC―2 load. 3. The man’s body acclimation to hyperthermia didn’t decrease the central activation ratio of muscle, while applying the MVC―2 load. 4. The man’s body acclimation to hyperthermia decreased the electric activity of the haunch muscle, while applying the MVC―2 load