Exercise Adaptations Based on Environment Flashcards
Define thermoregulation
- normal body temperature fluctuates several degrees during the day in response to physical activity
What happens to the body when stimulated by cold
- heat loss decreases through vasoconstriction & curling up
- heat production increases through shivering & increased voluntary activity
What happens to the body when stimulated by heat
- heat loss increases through sweating
- heat production decreases through decreased muscle tone & decreased thyroxine & epinephrine secretion
Where is the central coordinating center for temperature regulation
- in the hypothalamus
What is the normal body temperature range
37 degrees C +/- 1 degree C
How are temperature regulating mechanisms activated
- thermal receptors in the skin provide peripheral input to the hypothalamic central control center
- temperature changes in blood that perfuses the hypothalamus directly stimulate the hypothalamic control center
What factors regulate body temperature during cold exposure
- vascular adjustments
- muscular activity
- hormonal output
What are the 4 potential avenues for heat exchange when exercising
- radiation: magnetic waves being transmitted
- conduction: transmission through contact
- convection: transmission through circulation
- evaporation: provides the major physiologic defense against overheating
What 3 factors does sweat evaporation from the skin depend on
- surface exposed to the environment
- temperature & relative humidity of ambient air
- convective air currents around the body
Why does maximal cardiac output & aerobic capacity decrease during exercise in the heat
- because the compensatory increase in heart rate does not offset the decrease in stroke volume
Circulatory adjustments when exercising in the heat
- oxygen delivery to active muscles increases
- peripheral blood flow to the skin increases
Vascular constriction & dilation when exercising in the heat
- adequate skin & muscle blood flow during heat stress occurs at the expense of other tissues that temporarily compromise their blood supply`
Maintaining blood pressure when exercising in the heat
- arterial blood pressure remains stable during exercise in heat because visceral vasoconstriction increases total vascular resistance
What takes procedure over temperature control during exercise in the heat
- circulatory regulation & maintenance of muscle blood flow
What are the 3 heat dissipating mechanisms
- circulation: serves as workhorse for thermal balance
- evaporation: sweating begins sec after initiation of vigorous exercise
- hormonal adjustments: heat stress initiates hormonal adjustments to conserve electrolytes & fluid lost in sweat
What is the sweat loss peak for an acclimatized person
- peak is about 3 L per hour during intense exercise in the heat and averages nearly 12 L on a daily basis
What are the consequences of dehydration
- reduced plasma volume, increases HR, perception of effort, & core temperature
- when plasma volume decreases, peripheral blood flow & sweating rate decrease making thermoregulation more difficult
- after load also increases
What factors affect sweat-loss dehydration
- exercise intensity
- exercise duration
- environmental temperature
- solar load
- wind speed
- relative humidity
- clothing
What factors affect heat tolerance
- acclimatization: repeated exposure to hot environments
- exercise training: increases sweat response sensitivity & capacity
- age: older adults have a reduced thirst drive & children have a lower sweating rate & higher core temp.
- gender: women have more sweat glands, use circulatory cooling more than evaporative cooling, have a larger ratio of body surface to mass, & menstruating women will heat up more until they can release
- excess body fat: insulates the body’s shell to slow heat conduction to the periphery
How much faster does the body loss heat in cool water when compared with air at the same temperature
- 2 to 4 times faster in cool water