PhD, Associate Professor L.A. Romanova¹
Dr.Biol., Professor Yu.N. Romanov¹
Dr.Hab., Professor A.V. Eganov¹
I.A. Komkova^1
1South Ural State University (National Research University), Chelyabinsk

Keywords: female students, fitness, skin temperature, infrared thermography, fat mass.

Introduction. Human skin is a unique membrane that changes its temperature during heat loss and heat gain driven by the ever-changing internal and external environmental factors. Body temperature is maintained at a relatively constant level, despite temperature changes in the external environment. Temperature changes in the body tissues, organs, and systems are indicative of the energy metabolism rate. Skin temperature measurement provides useful information about the complex thermal control systems and the relationship between temperature profiles and metabolic parameters in athletes [1, 4].

Skin temperature, as noted by A.G. Shusharin et al., is an integral indicator, formed by the vascular tree (arteries and veins, lymphatic system), metabolic rate in the body organs and thermal conductivity of the skin. An increase in the blood flow, or, conversely, its decrease, caused by the vessel constriction or vascular occlusion, leads to an increase or decrease in the tissue temperature [5].

Thermoregulation is a multi-level system working to maintain the constancy of the internal environment of the human body, which is built on the unity and interaction of the peripheral and central links of the hypothalamus with the impact on the hypothalamic "centers" and the central nervous system divisions. The hypothalamus is a thermal detector of this system. Thermoregulation is carried out through the sensory inputs from the central and peripheral nodes [2].

There are two categories of skin thermoreceptors: cold receptors, located superficially - within 0.17 mm, and warm receptors, found deeper - up to 0.3 mm. The thermoreceptors respond to the temperature changes by increasing the frequency of the generated impulses being steady-state at the time of the stimulus exposure [3, 6].

The theoretical analysis revealed that the mechanisms in separate anatomical segments of the body of the female students engaged in fitness with different percentages of the total adipose tissue have been studied insufficiently.

Objective of the study was to characterize the skin surface temperature distribution in separate anatomical segments of the body in female students engaged in fitness with different percentages of the total adipose tissue.

Methods and structure of the study. For the purpose of the study, in 2017, a total of 109 full-time female students from different academic fitness groups (step aerobics, shaping, hip-hop, dance, artistic gymnastics, etc.) with different sports experience (2 to 10 years) were examined. The group was divided into two subgroups: low-fat group (n=20) and high-fat group (n=20). The participants with an average adipose tissue mass (n=69) were ignored. The female students’ mean age was 19.3 years, the differences in the age or body length in either subgroups were statistically insignificant.

Infrared thermography is a non-invasive, safe method to examine patients using a special device - a thermal imaging camera that helps detect infrared radiation and convert it into an image on the screen in the form of a thermogram. It registers the heat distribution on the surface of the body. The thermal imaging camera measures the temperature of the local anatomical segments of the body [7].

The laboratory study was conducted indoors, without air handling, thermal sources, the air temperature being 20-22 °C before noon. At the beginning of the study, the subjects underwent temperature adaptation indoors for 15-20 minutes. The distance between the subject and the thermal source was 2 m; the thermal source was fixed on a 140cm high clamp stand. At the time of the experiment, all subjects wore two-piece bathing suits; they were in a state of muscular rest and were examined in a standing position not earlier than 1.5 hours after meals, being apparently healthy.

The skin temperature was measured by means of the non-invasive method of infrared thermography using the Baltech TR-01500 thermal imaging camera (Germany). This method is based on the use of photodetector array, that makes it possible to read the information on the temperature of particular anatomical segments of the body element-by-element with subsequent electronic processing of the image obtained. The received data is used to make a thermal map of body areas, which is deemed by us as a certain standard for the corresponding age group and type of motor activity.

The body fat percentage was determined using the Tanita BC-418MA bioelectrical impedance analyzer, which determines the parameters of body composition. The body fat percentage was determined accurately within 5%.

The research was conducted at the premises of the Sports Science Research Center of South Ural State University (National Research University), Chelyabinsk, in 2017, under the supervision of Dr.Biol., Professor V.V. Erlikh, Dr.Biol., Professor A.P. Isayev.

Results and discussion. The infrared thermography revealed that the subjects had few or no similar skin temperature values in different anatomical segments of the body. There was an insignificant mosaic distribution of the skin temperatures. It was R.S. Andreyev who discovered the mosaic type of the body surface temperature distribution. He detected individual diversity of this mosaic, as well as a close correlation between the temperature profile and body build [1].

Table 1 presents the results of the statistical comparison of the female students engaged in fitness with different body fat percentages in various anatomical segments of the body.

Table 1. Statistical comparisons of the female students engaged in fitness with different total body fat percentages (±m)

Note. ±m - mean value, ± error of mean; ≤ - differences are statistically significant, boldfaced. It is the values of the right extremities only that are indicated, those of the left extremities have a similar tendency.

As Table 1 shows, in terms of the temperature in particular anatomical segments of the body, the female students with a relatively low body fat percentage differ statistically significantly in a number of indicators from the group of high-fat students (t=2.11-13.6, p≤0.04-0.001).

In the low-fat group, we found the statistically significant differences in the skin temperature values toward larger numbers in the following body segments: back side of the right forearm, right shoulder blade, right shoulder triceps, right arm biceps, right intercostals, right thigh quadriceps, right thigh biceps.

This is due to a higher rate of metabolism in the group of low-fat female students.

Other body segments: abdomen, right outer thigh, right gluteal fold, right anterior shin, side deltoid of the right shoulder in the low-fat group - have a similar tendency to increase in terms of the numerical temperature values; however, the differences are insignificant (t=0.75-1.91, at р≥0.06-≥0.46).

Similar data were obtained by A.C. Salamunes, A.M-W. Stadnik, and E.B. Neves. The authors studied the effect of body fat percentage on the skin of 26.11 year-old females using the infrared thermography technique. It was found that fat mass percentage in each body segment determines the body-segment-specific skin temperature distribution profiles [8].

Conclusions. In the academic fitness group female students, the skin temperature increases in the zones of hyperreaction to physical stress, first and foremost, in those muscle groups where the body fat percentage that can shield the radiation of heat from the body decreases, and second, in those muscle groups that are actively involved in the fitness training process.

Remote infrared thermography makes it possible to indirectly estimate the metabolic reaction rates in various anatomical segments of the body of students, which can serve as an objective sports monitoring technique.References

1. Andreev R.S. Vzaimosvyaz kharakteristik infrakrasnogo temperaturnogo portreta s metabolicheskimi pokazatelyami u sport­smenov. Avtoref. dis. kand. biol. nauk [Correlation of characteristics of infrared temperature profile with metabolic parameters in athletes. PhD diss. abstract]. Moscow, 2012, 20 p.
2. Bacherikov A.N., Kuzminov V.N., Tkachenko T.V. et al. Sovremennye predstavleniya o sisteme termoregulyatsii [Modern concepts of thermoregulation system]. Visnik psikhIatriii ta psikhofarmakoterapiii, 2006, no. 1, pp. 178-182.
3. Ivanov K.P. Bioenergeticheskie mekhanizmy gomoyotermii [Bioenergetic mechanisms of homeothermy]. Obshchaya biologiya, 1990, vol. 51, no. 1, pp. 11-20.
4. Semenov M.M. Dinamika temperatury kozhnogo pokrova futbolistov v protsesse trenirovochnoy i sorevnovatelnoy deyatelnosti [Skin temperature dynamics in football players in training and competitive processes]. Teoriya i praktika fiz. kultury, 2010, no. 12, P. 42.
5. Shusharin A.G., Morozov V.V., Polovinka M.P. Meditsinskoe teplovidenie – sovremennye vozmozhnosti metoda [Medical thermal imaging - modern capabilities of the method]. Sovremennye problemy nauki i obrazovaniya, 2011, no. 4. [Electronic resource] (date of access: 03.01.2018).
6. Yaichnikov I.K. Fiziologicheskie indikatory gomeostaticheskoy nadezhnosti organizma sportsmena – ‘temperatura’ [Physiological indicators of homeostatic reliability of athlete's body – ‘temperature’]. Uchenye zapiski un-ta im. P.F. Lesgafta, 2009, no. 6 (52), pp. 102-106.
7. Bichinho, G.L., Gariba M.A., Sanches I.J. et al. A computer tool for the fusion and visualization of thermal and magnetic resonance images. J. Digit. Imaging, 2009, vol. 22, no. 5, pp. 527–534. 36.
8. Salamunes A.C.C, Stadnik A.M-W, Neves E.B. The effect of body fat percentage and body fat distribution on skin surface temperature with infrared thermography. Journal of Thermal Biology, 2017, vol. 66, pp. 1-9.

Corresponding author: eganov@bk.ru

Abstract

The authors believe that individual skin temperature, being relatively constant, may be indicative of energy metabolism and, hence, skin temperature variations provide useful data on the complicated heat control systems; and on the correlations of individual temperature profiles with metabolic rates on the whole and physical activity in particular. The study obtained and analyzed the body-segment-specific skin temperature distribution profiles. Subject to the tests were the full-time female students (n=109) from the academic fitness groups classified by the body fat percentage. The study found the low- and high-fat groups being different in their body-segment-specific skin temperature distribution profiles. The low-fat group was tested with the significantly higher average temperatures versus the high-fat group in the following body zones: on the back sides of both forearms; both shoulder blades; both shoulder triceps; both arm biceps; right and left intercostals; both thigh quadriceps; and both thigh biceps.