PHYS ED 32 Lecture Notes - Lecture 10: Basal Metabolic Rate, Heat Stroke, Cramp
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22 Apr 2019
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Environmental Concerns in Exercise
I. Homeotherms
A. Hypothalamus in brain responds to temperature of blood (too warm, too cool)
1. VasoDilate or VasoConstrict blood vessels
a) VasoDilate: To expand/dilate--to increase blood flow; move more
blood to surface of skin
b) VasoConstrict: To clamp down/constrict blood flow to core of body
(organs of survival, like heart, lungs & brain)
B. Heat Balance -- normal range
1. 96.8 → 98.6 → 100.4 degrees
a) Heat Production
(1) BMR (Basal Metabolic Rate) [resting]
(a) Muscular Activity
(b) Hormones
(c) DIT
b) Heat Loss
(1) Radiation
(2) Convection -- losing heat to air that may be moving across
skin at speed, or losing heat surrounding by water
(3) Conduction -- Transferring heat to some object that you
are sitting on
(4) Evaporation -- Way we turn water into water vapor (cooling
effect)
(a) Primary way = sweating
II. Exercise in Hot Weather
A. Bodies response to heat, humidity
1. Increase in heart rate
2. Increase in sweating
a) Humidity = measure of water content in air
B. Heat Injuries (heat exhaustion, heat stroke)
1. Heat Exhaustion:
a) Faint or dizzy
b) Excessive sweating
c) Cool, pale, clammy skin
d) Nausea, vomiting
e) Rapid, weak pulse
f) Muscle cramps
2. Heat Stroke
a) Throbbing headache
b) No sweating
c) Body temp above 103 degrees
(1) Red, hot, dry skin
d) Nausea, vomiting