Prediction and Prevention of Physiological Risk Factors During Intensive Exercise in a Hot...

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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: irena.yermakova@gmail.com

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.

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