Dr.Biol., Professor Y.N. Romanov¹
Associate Professor, PhD A.A. Pletnev¹
Associate Professor, PhD E.V. Zadorina¹
E.F. Baymukhametova^1
1South Ural State University (National Research University), Chelyabinsk

Keywords: skin temperature, thermotaxis, homeostasis, heat adaptation, female students.

Introduction. According to research, one of the most important types of homeostasis for the human body is maintaining optimal body temperature controlled mainly by the hypothalamus [7]. The significance of thermotaxis is justified by the fact that its efficiency coefficient (EC) in humans is more than 13 times higher than that of the baroreceptor regulation of blood pressure [1]. However, physical exercises and repeated stress can become an obstacle to thermal homeostasis [8].

Under various environmental conditions, the main mechanisms of heat adaptation are aimed to both enhance body heat dissipation and maintain its heat balance during cooling [2-5]. In sports practice, there are situations when the time of completion of warm-up and start of a competitive exercise does not add up for various reasons (announcer call, preparation of sporting equipment, recording equipment failure, etc.)., The body of athletes can cool down enough in between these pauses to result in decreased physical working capacity and, consequently, poor sports performance. Among the relevant tasks of sports physiology is to forecast the dynamics of changes in man’s functional state when cooling as a reaction to low temperatures.

Objective of the study was to analyze the influence of physical fitness indices on thermotaxis in female students of two comparison groups.

Methods and structure of the study. The study involved the 17-19 year-old female university students divided into 3 groups. Group 1 (n₁=20) was made of the Candidates for Master of Sport in various types of fitness, Group 2 (n₂=126) – of the non-sporting female students, engaged in fitness trainings twice a week. The first stage of the experiment was aimed to determine the percentage fat tissue mass (PFTM) in the body of female students of both groups (n₁=20, n₂=126) using Tanita BC-418 MA analyzer. The mean PFTM value in the female students equaled 21.83±1.91%. Then, by comparing the individual PFTM values ​​in the total sample of non-sporting female students of both groups, we formed a group (n₃=20) with a mean intergroup PFTM value equaling 22.07±0.75%. The mean PFTM values in two comparison groups (n₁ and n₃) did not differ statistically significantly (p≤0.05). The second stage of the experiment consisted in infrared thermography measurement using BALTECH TR-01500 Thermal Imaging System and involved the female students of both groups (n₁ and n₃). The measurement was taken before warming up (single exposure) and during 170s relaxation after 15min warm-up of medium intensity causing ephidrosis (exposure every 10 s). In our previous studies [6], the data obtained indicated an inverse correlation between the skin temperature and PFTM value. Therefore, we formed the study groups with PFTM that did not differ statistically significantly (p≤0.05). For the purpose of statistical processing, from the entire temperature data array, we selected the data on ten muscle groups most actively involved in the execution of sports and fitness activities.

Results and discussion. The girls dressed in sheer swimsuits were subject to a series of exposures with the thermovision camera at a humidity of 40% and air temperature of 20-21°C, which is 10-13°C below the thermoneutral zone temperatures. This caused the activation of the sympathetic division of the autonomic nervous system, which, in turn, led to adiaphoresis, decreased vasoconstriction and, as a result, reduced heat dissipation. Based on the data represented as average temperatures of the above mentioned muscles, we used Microsoft Excel spreadsheet application to build the average temperature curves for two groups of female students for the time marks as follows: 0, 20, 40, 60, 80, 100, 120, 140, 160 s - for the front view, and 10, 30, 50, 70, 90, 110, 130, 150, 170 s - for the posterior view (a total of 18 exposures). The behavior of the temperature curves of all muscle groups under study, except for the trapezoid, was identical for two groups of subjects. The figure illustrates the changes in the average skin temperatures of the front surface of the thigh, uniting the following muscle group (m.): rectus m. of thigh, medial vastus m., lateral vastus m., tailor's m. Fine differentiation of the chemical thermogenesis displays in the female students of Group 1 throughout the entire rest pause enabled to keep the skin temperature at the same level. In the female students of Group 3, starting from the first exposure of the thermovision camera, the average temperature decreased to the 10s time mark, which differed significantly from the temperature curve in Group 1, after which thermogenesis was activated to maintain the heat balance.

Changes in the mean skin temperature on the front surface of the left thigh during relaxation after warming up in two comparison groups (n₁=20, n₃=20).

Conclusions:

• The high level of physical fitness contributed to the improvement of the ability to quickly activate thermoregulatory mechanisms in response to moderate cooling, which indicates a more balanced thermal homeostasis in the female students of Group 1.
• The heat balance control system in the female students of Group 1 was better adapted to moderate cooling, which is essential to the effective muscle activity
• The female students of Group 3 demonstrated insufficient work of their adaptive thermoregulatory systems due to excessive ergo-thermal load, which does not correspond to the female athletes’ adaptive capabilities.

The article was supported by the government of the Russian Federation (Act No. 211 of 03/16/2013), Agreement No. 02.A03.21.0011.

References

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Corresponding author: romanovyn@susu.ru

Abstract

According to research, one of the most important types of homeostasis for the human body is maintaining optimal body temperature controlled mainly by the hypothalamus. The study analyzes the influence of physical fitness indices on thermotaxis at modestly low temperatures in female students. Thermograms were generated by BALTECH TR-01500 Thermal Imaging System, with infrared images of the Group 1/ 3 students’ skin temperature. The highly physically fit Candidate Masters of Sport (n₁=20) were tested with much better thermal regulation rates versus the non-sporting female students (n₃=20) under physical loads. The student Group 1 body temperature regulation strategy following a 170s warm-up and relaxation was found quite efficient, in contrast to the student Group 3 that was tested with the significant fall in the skin temperature.