Human body behavior by thermovision analysies in standing and gait processes.

Baritz, Mihaela ; Cristea, Luciana ; Cotoros, Diana 等

1. INTRODUCTION

Human body is a good example of thermal adaptation to different environmental conditions and represents a way of keeping its temperature constant even the daily activities are develop in different working or living fields.

The heat of human body is kept inside, conserved even it is in low temperature environments.

If the adaptation process mentioned is insufficient, contracting the muscles additionally, they produce shivering and the human body produces additional heat.

In warm conditions of environments, an organism needs to lose extra heat from inside; for that the blood vessels expand and blood flow toward the skin is increased, increasing also the skin surface temperature.

In different human body actions like gait, running, jumping or other dynamical activities there are an important heat quantity develop and need to eliminate it because the thermoregulation is a continues necessary process for thermal adaptation. (http://hyperphysics.phyastr.gsu.edu)

Normal walking process causes many changes to neuromuscular system of a human body restricting his stability capabilities and increasing his body temperature.

It is very important to study the changes in the working or living activities of subjects especially when these activities are daily movements and develop a substantial quantity of heat.

Because these changes sometimes result in an increase the number of back pain and neuromuscular disorders or falls during daily walking it is very necessary to analyze the influence of the thermal "points" on the hall human body stability and gait (static and dynamic).

Many researchers studied stability of human gait and it was quoted that human walking gait stability, for example, decreases with the increase of working time and with the age increasing the risk of falls in worker people category.

Many studies have been reported about the change in the kinematics parameters with age but they require complex systems and experiments can only be performed in the laboratory environments. (Baritz, 2002)

2. THEORETICAL ASPECTS

2.1 Force plate

The ground reaction force is an important external force, which constantly affects the human motions, like stability in standing positions, walking or running. Force-plates are commonly used in measuring the ground reaction force when human foot is in contact with it. One of the most important issues in ground reaction analysis is the coordinate system.

Most manufacturers of the force plates use the action system for stability analysis while the reaction system is used in the motion analysis. The reaction force supplied by the ground is the ground reaction force and this force, along with the weight, is an important external force. The ground reaction force has three components: [F.sub.x], [F.sub.z] and [F.sub.z]. These forces are, [F.sub.y]--along the direction of the motion which reflects the propulsive or braking force, Fz--always thrusts the body upward and--a force for establish the stability into a perpendicular plan to the moving direction.

2.2 Equivalent, standard and subjective temperature Equivalent temperature is calculated and defined like temperature in uniform thermic environment, at which, a heat loss equivalent to the heat loss in the real environment is caused. The uniform thermal environment represents the uniform space where the air temperature is equal to the mean radiant temperature, the air current is steady, and there is no vertical gradient in temperature. The relation proposed by Bedford (1936) to calculate equivalent temperature is following: (Kazuhiko & Tohru, 2004),

[T.sub.eq] = [0,522T.sub.a] + [0,478T.sub.r] - 0,21[square root of V](37,8 - [T.sub.a]) (1)

Standard operative temperature proposed by Gagge (1940)

is defined like a complex equation. This equation is the first trying to evaluate the effects of environments in purpose of evaluating physical thermal radiation from a human body.

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (2)

The subjective temperature is a kind of equivalent temperature proposed by McIntyre (1976) and this subjective temperature is an index near to a real thermal sensation when the equation is used depending on air velocity.

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (3)

3. EXPERIMENTAL SETUP

To use the human body in stability by thermovision dynamic studies it is necessary to analyze, in the first step of these researches, the anthropometrical dimensions of the locomotor system and make measurements on the body segments.

[FIGURE 1 OMITTED]

The experimental setup used in these investigations was establishing according with each sort of investigations and it can be adapted in function with different patient. In this paper it is present the case of a patient with gait disabilities. These gait disabilities are given by the musculature stress, because she is after a period when she was wearing, at the left leg, a gypsum bandage. After the measurements about de body segments it is also important to establish the main thermal points on the surface human skin to survey these points in gait process. The procedure of investigations was establishing in concordance with her metabolism, her entire health and with environmental conditions in the way to obtain the best results of investigations. We were used a force plate system with 4 piezoelectric sensors, amplifier, a thermovision video-cam and electrophysiological apparatus. These measurements on human body and environment establish the methodology to investigate the thermal behavior of the human body and they are repeated for ten times in the same day to obtain the average values. In the same time was necessary to keep under control the environmental temperature, without any airflow, or changes in the sunlight influences. There are a good correlation between mean skin temperature and the thermal sensation and thermal comfort of a human body. When local skin temperatures are not uniform, in the case of evaluating heat exchange between the human body and the environment or thermal sensation of the whole body, could be used some methods to average local skin temperatures. Some researchers have proposed various formulas for calculating the mean skin temperature using arithmetical averages and using a weighting factor for the ratio of skin area. (Yuka et al., 2006)

4. RESULTS AND CONCLUSIONS

When calculating heat exchange between the human body and the surrounding environment is used mean skin temperature, which represents the average skin temperature of the entire body surface. In general, skin temperature is not uniform across the entire body surface, and as a result, means measuring the skin temperature of a certain area of the body and then calculating the ratio of that area to the total body surface area determine skin temperature. In other words, mean skin temperature has traditionally been calculated assuming that skin temperature is fairly uniform over the entire body. While the number and location of temperature measurements vary, it is necessary to measure skin temperature on areas of the body exposed to the surrounding environment and to consider skin temperature distribution. It is body obvious that as far as skin temperature distribution is concerned, the greater the number of skin temperature measurements, the greater the accuracy of the calculation.

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But, sometimes, it is not always practical to measure skin temperature at multiple points because in this time the human body can equilibrate the skin temperature with the environment temperature. (http://hyperphysics.phyastr.gsu.edu)

Because this patient has gait disabilities is obvious that the force developed on Ox and Oy axis have different values when it is used left or right leg and the moments on the Ox direction is biger when it was using the left leg, fig.4a, 4b. This value establish a disequilibrium on the left side and the temperature into the joint of the left leg increase during the gait process most quickly like in right leg and this process allow to modify the configuration and the effort consumption. Also the increasing of temperature into the leg's joint during the walking effort, induce some pain for patient and instinctively she wants to protect the left leg inducing other forces into right leg and increasing the possibility to fall down. For that she was doing other adaptive movements to establish the equilibrium and stability for human body. The force graphs on Oy direction developed by the right leg shows big variations from begin to end and the temperature values measured by thermovision were following these variations closely. (Kistler force plate, 2006)

After good rehabilitation program for these disabilities on the left leg, this patient can walk in better conditions and the temperature gradients measured on the human body show that, there are not any differences between her two legs, means she has a good stability in gait and standing activities.

5. ACKNOWLEDGMENT

Researches are part of Grant A1058/2008 with CNCSIS Romania, IDEI 722/2009 and IDEI 744/2009.

6. REFERENCES

Baritz, M. (2002), Study of the complex shape by complementary methods, Infomarket Publisher, Romania, ISBN 973-8204-26-7

Kazuhiko, M.; Tohru, M (2004), An analysis and examination of equivalent temperature, Journal of the Human-Environmental System, Vol.7, No.2, 2004

Yuka, H., Takeki, I., Hiroshi, M. and Ken A., Fundamental Study of Weighting Factors for Calculating Mean Skin Temperature, Journal of the Human-Environmental System, Vol.9, No.1-2, 2006

*** http://hyperphysics.phyastr.gsu.edu, Accessed: 2008-06-16;

*** Kistler force plate (2006), Operating Manual and software.