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Prediction and Prevention of Physiological Risk Factors During
Intensive Exercise in a Hot Environment
Irena Yermakova1, Alla Bogatenkova1, Nastia Nikolaienko1, Tanya Zilberter2
1International Research Training Centre for Information Technologies and Systems, National Academy of Sciences, Kiev, Ukraine
2Mediterranean Institute of Neurobiology, Marseille, France
E-mail: [email protected]
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.
Materials and MethodMulticompartmental 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
Computer Simulator
Human exercise
Activity velocity
300 W 1 m/s
450 W 1,4 m/s
600 W 1,8 m/s
750 W 2,2 m/s
900 W 2,6 m/s
Multicompartmental thermal models were implemented in an object-oriented approach and were realized as computer simulator for prediction of human thermal state.
Physical activity in dry hot environment
Air temperature 40C, humidity 20%
Cardiovascular system
hours
L/h
0.25 0.5 0.75 1
150
300
450
600
750
900
0
Muscles blood flow
450 W
600 W
750 W
900 W
300 W
hours
L/h
0.25 0.5 0.75 1
30
60
90
120
150
180
210
0
Skin blood flow
450 W
600 W
750 W
900 W
300 W
Adequate muscle blood flow for different physical activity.
hours
Beats/min
0 0.25 0.5 0.75 160
90
120
150
180
210
Heart rate
450 W
600 W
750 W
900 W
300 W
Cardiovascular systemAir temperature 40C, humidity 20%
hours
L/h
0 0.25 0.5 0.75 1200
400
600
800
1000
1200
1400
Cardiac output
450 W
600 W
750 W
900 W
300 W
Heart strain increases on exercise intensity.
W
*C
300 450 600 750 90037.25
37.5
37.75
38
38.25
38.5
38.75
Blood temperature
W
g
300 450 600 750 900500
750
1000
1250
1500
Water losses
Thermoregulatory system Air temperature 40C, humidity 20%
Intensive sweat evaporation prevents from high hyperthermia. All sweat is evaporated. No Dripping.
hours
g/h
300 450 600 750 900400
600
800
1000
1200
1400
1600
Sweat rate
Physical activity in humid hot environment
hours
g/h
0.1 0.2 0.3 0.4
400
800
1200
1600
0
Dripping sweat rate
Caution! Here is the problem!
Air temperature 40C, humidity 80%
Comparison of model and human calculations
Model Human
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.270
80
90
100
110
120
130
140
150
bpm Heart rate 700 W
hours t
0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.270
80
90
100
110
120
130
140
150
Heart rate bpm 700 W
hours t
semi-nude
cotton
PVC
heart rate
Air temperature 30°C Air humidity 35%
Intensity700W
Results
• the muscle demand is being prioritized and always met;
• skin blood flow, having a lowerpriority, is limited due to the heart pumping function constraint;
• hyperthermia and dehydration develop in proportion with exercise intensity and environment.
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.
THANK YOU FOR YOUR
ATTENTION!
