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
Describe acclimatization to cold
- repeated cold exposure of the hands & feet brings about blood flow increases through these areas during cold stress (vasodilation)
- individuals regulate at a lower core temperature in the cold
Do humans adapt more successfully to chronic heat exposure or regular cold exposure
- chronic heat exposure
What relationship does PO2 & barometric pressure have
- PO2 decreases proportionately to the decrease in barometric pressure
Immediate adjustments to altitude
- hyperventilation due to less O2
- body fluid become more alkaline due to reduced CO2 with hyperventilation
- increased submax HR
- increased submax cardiac output
- stroke volume stays same or lowers slightly
- max cardiac output remains the same or lowers slightly
Longer term adjustments to altitude
- hyperventilation
- excretion of base via the kidneys with reduced alkaline reserve
- submax HR remains elevated
- submax cardiac output falls to or below sea level values
- stroke volume lowers
- max cardiac output lowers
- decreased plasma volume
- increased hematocrit
- increased hemoglobin concentration
- increased total number of red blood cells
- possible increased capillarization of skeletal muscle
- increased mitochondria
- increased aerobic enzymes
Describe fluid loss at altitude
- altitude causes a depressed thirst sensation
-the cool, dry air in mountainous regions causes considerable body water to evaporate as air warms & moistens the respiratory passages
Define acute mountain sickness (AMS)
- relative benign condition that becomes exacerbated by exercise in the first few hours of exposure, treatment usually involves rest & gradual acclimatization
Define high altitude pulmonary edema (HAPE)
- involves fluid accumulation in the brain & lungs, requires immediate descent to lower altitude on a stretcher or flown to safety
Define high altitude cerebral edema (HACE)
- possible fatal neurological syndrome that develops within hours or days in people with AMS (acute mountain sickness), requires immediate decent to lower altitude & supplemental oxygen administration
Define high altitude retinal hemorrhage (HARH)
- hemorrhage in the macula of the eye produces irreversible visual defects, immediate decent to a lower altitude with supplemental oxygen or use of a hyperbaric chamber
Define Gamow bag hyperbaric chamber
- a portable chamber to treat altitude sickness by stimulating lower altitudes
When do small declines in VO2 max become noticeable at altitude
- at 589 meters of altitude
At what altitude do you see decrements in events lasting 2-5 minutes
- at 1600 meters altitude
At what altitude to you see decrements in events lasting longer than 20 minutes
- between 600 & 700 meters of altitude
Describe “live high, train low”
- live high meaning live at higher altitudes so the you get the benefits
- train low meaning train at lower altitudes so that you’re able to reach high intensities
Space has similar effects on the body as bed rest does (True/False)
- True
Physiological effects of space flight
- space motion sickness
- neurovestibular dysfunction
- fluid redistribution to upper body & head
- decreased cardiovascular efficiency
- increased negative Ca++ balance
- decreased blood plasma
- increased renal stone risk
- increased radiation doses
- decreased muscle strength
- decreased bone density
How much bone loss is experienced with spaceflight, Type I osteoporosis (post-menopause), & Type II osteoporosis (age related)
- spaceflight loses 0.5-2% per month
- Type I osteoporosis loses 20% total over 5-7 years or 3-4% per year
- Type II osteoporosis loses about 1% per year
Muscle response to spaceflight without resistive exercise for 2-3 months
- leg muscle cross sectional area decreases about 30%
- leg strength decreases about 50%
- shift occurs from slow to fast fiber types
- back muscles become weak, soft tissues at risk of injury
- contraction & relaxation times decrease
- fatiguability increases
Post flight effects/recovery
- fluids shift to lower extremities
- EDV decreases causing increased HR
- control of BP may not be adequate
- syncope potential
- weakened leg muscles results in reduced venous valve blood pumping action
- anemic like conditions after rehydration
Boyles Law
- as pressure increases, gas volume decreases
Describe what happens during the descent into a hyperbaric environment (under water)
- external pressure increases & air already in the body compresses
Describe what happens during the ascent out of a hyperbaric environment (under water)
- air taken in at depth expands
- if breath is held while ascending, lungs may over distend leading to spontaneous pneumothorax (lungs collapse)
Define barotrauma
- tissue injury caused by changing pressure
Define decompression sickness
- N2 bubble formation during ascent
Cardiovascular responses to immersion
- cardiovascular workload decreases due to increased venous return
- plasma volume increases
- HR decreases
- at a given exercise effort, HR is lower
Describe ventilation during diving
- ventilation may be the limiting factor during diving due to the smaller lung volumes & increased density of the air
Individuals with larger TLV: RV (total lung volume:risidual volume) ratios can dive deeper than those with smaller ratios (True/False)
- True
Describe oxygen toxicity (poisoning)
- PO2 values exceed 318 mmHg
- visual distortion, rapid & shallow breathing, & convulsions
- tissues are not able to remove O2 from hemoglobin causing hemoglobin to not remove CO2
- high PO2 causes vasoconstriction of cerebral vessels
Describe decompression sickness
- resulting from ascending too rapidly
- aching in elbows, shoulders, & knees
- N2 bubbles become trapped in body
- treat by placing diver in recompression chamber
Describe saturation diving
- by staying in a pressurized environment for 24 hours, the body tissues become saturated, after which the tissues do not absorb any more inactive gas allowing divers to stay at great depths for longer periods of time
Describe nitrogen narcosis
- nitrogen acts the anesthetic gas (N2O - laughing gas)
- similar to alcohol intoxication
