1. Prediction and Prevention of Physiological Risk Factors During Intensive Exercise in a Hot Environment Irena Yermakova 1, Alla Bogatenkova 1, Nastia Nikolaienko 1, Tanya Zilberter 2 1 International Research Training Centre for Information Technologies and Systems, National Academy of Sciences, Kiev, Ukraine 2 Mediterranean Institute of Neurobiology, Marseille, France E-mail: irena.yermakova@gmail.com

2. Background and Aim Physical exercise in hot environments is highly challenging for the cardiovascular system because of the concomitant physiological demands: 1) a necessity of increasing blood flow to the exercising muscles on one hand, 2) a simultaneous demand for the skin blood flow to draw the excess heat off the body on the other hand. An additional challenge is imposed by considerable dehydration and hyperthermia. This work aims to developing a predictive multicompartmental model for evaluation of cardiovascular and thermoregulatory risk factors during human physical work in the heat.

3. Materials and Method Multicompartmental computer model Modeling: - dynamic changes in the body's temperature, - skin and muscle blood flow, - heart rate, - cardiac output, - the rate of heat removal by evaporation, - the accompanying fluid loss and some of other cardiovascular and thermoregulatory parameters necessary. Exercise: intensity and duration, recruitment of the major muscle groups,activity velocity Ambient environment: air temperature, humidity, air velocity

4. Computer Simulator Human exercise Activity velocity 300 W1 m/s 450 W1,4 m/s 600 W1,8 m/s 750 W2,2 m/s 900 W2,6 m/s Multicompartmental thermal models were implemented in an object-oriented approach and were realized as computer simulator for prediction of human thermal state.

5. Physical activity in dry hot environment Air temperature 40C, humidity 20% Cardiovascular system 450 W 600 W 750 W 900 W 300 W 450 W 600 W 750 W 900 W 300 W Adequate muscle blood flow for different physical activity.

6. 450 W 600 W 750 W 900 W 300 W Cardiovascular system Air temperature 40C, humidity 20% 450 W 600 W 750 W 900 W 300 W Heart strain increases on exercise intensity.

7. Thermoregulatory system Air temperature 40C, humidity 20% Intensive sweat evaporation prevents from high hyperthermia. All sweat is evaporated. No Dripping. hours g/h 300450600750900 400 600 800 1000 1200 1400 1600 Sweat rate

8. Physical activity in humid hot environment Caution! Here is the problem! Air temperature 40C, humidity 80%

9. Comparison of model and human calculations Model Human heart rate Air temperature 30°C Air humidity 35% Intensity700W

10. Results the muscle demand is being prioritized and always met; skin blood flow, having a lower priority, is limited due to the heart pumping function constraint; hyperthermia and dehydration develop in proportion with exercise intensity and environment.

11. CONCLUSIONS A modelling of human physiological responses to specific parameters of exercise in challenging environments can be a useful tool for the prevention of health risk factors in potentially hazardous environments.

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