Environmental Exercise Physiology Flashcards
1
Q
How rapid can muscles warm?
A
By 2-3 degrees in endurance and resistance exercise
2
Q
What is the effect of warm/hot muscles on force and power?
A
- Warm muscles can produce more power
- Hot muscles can produce less force and fatigue faster
3
Q
What does muscle temperature depend on?
A
- Time
- Intensity
- Clothing
- Tambient
4
Q
What effect does warm/hot muscles have on strength and single sprints?
A
Strength and single sprints improved, but repeated sprinting impaired with increasing ambient heat stress
5
Q
Does hot environments impair endurance performance?
A
Yes, a cool environment is usually a benefit. The best environment to maximises time to exhaustion is 11 degrees
6
Q
What does the optimal temperature for aerobic exercise depend on?
A
- Medium (water or air)
- Exercise intensity
- Clothing
- Body composition
- Body size
- Exercise mode
7
Q
What are the 3 problems with heat?
A
- Thermoregulation reduces exercise capacity
- Thermoregulatory power is finite and limited by other effects of exercise on the body
- Heat-stroke can be fatal
8
Q
What is the most important determinant of your heat tolerance?
A
Your fitness
9
Q
What happens at 37 degrees?
A
The resting zone for sedentary versus athletes/acclimated
10
Q
What happens at 38 degrees?
A
Peak skin blood flow and sweat rate. Tolerance limit for some
11
Q
What happens at 39 degrees?
A
Tolerance limit for moderately trained (esp. if clothed)
12
Q
What happens at 40 degrees?
A
Tolerance limit for many athletes. Increased cell permeabilities
13
Q
What happens at 42 degrees?
A
Some athletes tolerant to this level
14
Q
What is the main detection and other receptors of body temperature?
A
Hypothalamus is the main detector. Other receptors are in the skin, spinal cord and your stomach
15
Q
What is body temperature in exercise governed by?
A
- Heat production
- Heat loss
- Initial Status
16
Q
What are the factors of heat production for body temperature in exercise?
A
- Duration
- Pattern
- Efficiency
17
Q
What are the factors of heat loss for body temperature in exercise?
A
- Physical (& behavioural) aspects: environment, clothing and movement
- Physiological responses: skin blood flow, sweating
18
Q
What are the factors of initial status for body temperature in exercise?
A
- Body temperature
- Body composition
19
Q
What are the factors that contribute to heat gain?
A
- Metabolism
If Tair > Tsk - Radiation (direct and reflected)
- Convection
- Conduction
20
Q
What are the factors that contribute to heat loss?
A
- Evaporation
If Tair < Tsk - Radiation
- Convection
- Conduction
21
Q
How much energy released in exercise is ‘wasted’ as heat?
A
75-100%; only ~25% yields work
22
Q
What is heat production rate equal to?
A
Heat production rate = Metabolic rate - work rate
23
Q
What does the capacity of the environment to absorb heat depend on?
A
- Water vapour pressure
- Radiant temperature
- Air movement
- Resistance to heat transfer
- Ambient temperature
24
Q
What is the most common way to represent the environmental effect in sport?
A
Wet bulb globe temperature (WBGT)
25
Why are hot or humid environments stressful?
- Harder to offload heat; esp. if low evaporative capacity
- Requires more sweat and skin blood flow
26
What are the physiological demands of exercise?
- Need increased muscle blood flow
- Then need increased skin blood flow and sweating
- But, also need to maintain arterial pressure and adequate blood supply to other tissues
27
What is the physiology of exercise in the heat? (9)
- Warmer periphery
- Increased skin blood flow and sweating
- Bigger decrease in blood volume
- Increased HR and decreased SV to maintain CO and MAP
- Increased stress hormones
- Increased muscle glycogen depletion
- Increased lactate production in muscle and blood
- Increased perceived effort
- Increased thermal discomfort
28
What does offloading heat effectively require?
Requires evaporating water (sweat) off skin
29
What limits performance under heat stress?
- Critical body temperature
- Rate of body warming (potentially)
- Cardiovascular strain
- Psychophysical strain
- Metabolic strain
30
What are the 4 major personal factors governing performance in heat?
1. Aerobic fitness
2. Heat acclimatisation
3. Initial physiological status
4. Hydration
31
What are other personal factors affecting performance in heat?
- (recent) illness
- Medications
- Body size
- Age
- Sex
- Fatigue and sleep deprivation
32
What are heat related illnesses?
- Sun burn
- Heat cramps?
- Heat syncope (fainting)
- Heat exhaustion
- Exertional heat stroke
33
What is the main feature of heat syncope (fainting)?
Especially if 1st day of exercise in the heat?
34
What is the cause of heat syncope (fainting)?
Inadequate vasoconstrictive and HR response to maintain BP
35
What is the main feature of heat exhaustion?
Exhaustion, hot, flushed, sweaty, rapid HR
36
What is the cause of heat exhaustion?
Homeostatic capacity exceeded, esp. of CVS system. Hypo hydration makes more likely. Metabolic and electrolyte depletions can be involved.
37
What is the main feature of exertional heat stroke?
Complete exhaustion with CNS disturbance
38
What is the cause of exertional heat stroke?
Major cellular disturbances, mainly due to increased Tbody & immune disturbances caused by exercise and/or illness
39
In which situations do you need to be wary of unusually high heat strain for individuals?
- The highly motivated, recreationally-fit athlete
- Intense practice sessions
- Recent or current illness
40
What are the strategies to decrease heat strain and increase performance?
- Increased aerobic fitness and heat acclimatisation
- Decreased clothing and carried weight
- Decreased exercise volume
- Optimise plasma volume and osmolality
- Artificial cooling
41
What problems can arise from cold stress for exercise?
- Impaired performance
- Discomfort
- Glycogen depletion
- Injury/illness
- Hypocapnia from hyperventilation
42
What determines net level of cold stress?
- Heat gain: Metabolic heat
- Heat loss: Evaporation, radiation, convection and conduction (If Tair < Tskin)
43
What is the effectiveness of behavioural responses to cold?
- Behaviour is the most powerful response eg. clothing
- Exercise very effective, except: in cool/cold water, fatigued
44
What are the 2 major physiological responses to cold?
- Vasoconstriction of skin and muscle (allows both to be insulators)
- Shivering is ok but can affect other processes (movement increases heat loss if in water, dilates blood vessels muscle)
45
What happens when core temperature drops to 33 degrees?
Resting comfort
45
What are the 2 minor physiological responses to cold?
- Counter-current heat exchange in limbs
- Non-shivering thermogenesis
46
What happens when core temperature drops to 15 degrees?
Onset of pain
47
What happens when core temperature drops to 12 degrees?
Decreased dexterity and strength
48
What happens when core temperature drops to 7-8 degrees?
Neural block: numbness, decrease power and strength
49
What happens when core temperature drops to -5 - -8 degrees?
Skin freezes
50
What is the cooling defence zone?
Provides feedforward drive for vasoconstrictive, and also contributes to drive for shivering. Reduced strength, power and dexterity
51
What are the effects of core cooling at 37 degrees?
Resting core temperature zone for sedentary vs athletes/acclimated
52
What are the effects of core cooling at 36 degrees?
Moderate shivering; reducing strength, power, dexterity
53
What are the effects of core cooling at 35 degrees?
= Hypothermia: Maximal shivering and decreased performance
54
What are the effects of core cooling at 33 degrees?
Cardiac arrhythmias; highly variable inter-individual responses
55
What are the effects of core cooling at 29 degrees?
Severe cardiac arrhythmias and unconsciousness common
56
How do cold stress responses affect exercise variables?
- Decrease peripheral temperature (decreases sensory and motor function)
- Increase metabolic rate (increased energy consumption, hastening fatigue)
57
What are hand and foot temperatures governed by?
- If body is in positive heat balance overall
- Clothing coverage
- Local muscle activity
58
Who is most at risk during exercise in cold conditions?
- Small, ectomorphic body shape
- Young
- Elderly
- Sedentary people
- Males or females?
59
What is habituation?
Humans do not adapt cold defence with repeated cold stress, instead, we cool faster while feeling more comfortable (habituation)
60
What are the specific hazards with cold?
- Immersion into water
- Prior exercise/heat stress
- Hypothermia
61
What is the hazard with immersion into water?
- People cool faster in water
- Cold shock response
- Incapacitation
- Autonomic conflict
62
Is exercise good or bad in 28 degree water?
Beneficial
63
Is exercise good or bad in 20 degree water?
Beneficial for some (especially fat and fit) but cools others
64
Is exercise good or bad in 10 degree water?
Detrimental
65
What happens to the body during exercise in cool and cold water?
- Body's insulation is degraded
- Increased blood flow through muscle and fat
- Boundary layer broken
- Also increased exposed surface area
66
What is the hazard with prior exercise/heat stress?
- Cool faster during cold stress
- Can decrease energy capacity
- Due to decreased insulative capacity
67
How long does it take hypothermia to develop?
- Doesn't usually develop as quickly as you would expect
- Might take 30mins to reach hypothermic state
- But for competitive swimmers, it could take 20 mins due to swimming faster which increases convection
68
What are the symptoms of hypothermia?
- Cold and shivering
- Disorientation
- Obvious alteration in mood, lethargy
- Muscle weakness
- Symptoms are variable
69
How can you prevent hypothermia?
- Planning
- Proper behaviour/clothing
- Monitor environmental conditions
- Fitness
- Awareness of individual differences in tolerance
70
What is the treatment for hypothermia?
- Prevent further cooling, initiate re-warming: remove wet clothing, dry skin, then insulate person
- Focus if possible first on warming: core and torso
- Be aware of ongoing core drop
- Take care when removing people from cold water if long immersion
71
What are the potential benefits from repeated cold stress?
- Recovery from overly-strenuous exercise
- Repeated cold shock (very powerful stress activation)
- Anti-depressant
- Brain-modulating/growth proteins
- Browning of white fat
72
What are the environmental stressors at high altitude?
- Decreased PO2 (due to less air)
- Lower temperature
- Lower humidity
- Less liquid water
- Increased wind
- Higher UV radiation
73
What are the physiological effects at higher altitude?
- Increased ventilation
- Less fluid and energy in
- Increased glycolysis and energy use
- Decreased gut absorption
- Increase catabolism
74
What are the potential results of higher altitude environment?
- Hypoxia
- Hypothermia
- Hypohydration
- Hypoglycaemia
75
What are the practical and performance effects of high altitude?
- Lower VO2max and anaerobic threshold so lower training intensity
- Higher CHO needs but lower appetite (nausea)
- Psych stress, boredom, less sleep, less cognitive and perceptual functions
76
What is the physiological stress at higher altitude environments mainly due to?
Limited PO2 diffusion gradient
77
What is the effect on aerobic power with altitude 0-1500m?`
No effect. But is affected by ~1% each 100m thereafter
78
Who are most affected by higher altitude?
Aerobically fit people are most affected, but they still have higher capacities to survive and move (the lack of oxygen affects them more than less fit)
79
What are the acute and adaptive responses to altitude?
- Acute responses are cardiorespiratory
- Increase HR and minute ventilation at rest and submax exercise
- Then begin to increase haematocrit as fluid is lost
- Adaptive responses also include peripheral changes
80
What are the overview of responses to altitude?
- Generally, the level of response is proportional to level of altitude
- Large inter-individual variability in acute and adaptive responses
- Successful adaptation must be graded
- Necessarily involves reducing exercise intensities
81
What is the 1st response to higher altitude?
Hyperventilation - because there is lower oxygen pressure so you need to stimulate your breathing
82
What is the effect of hyperventilation on the acute responses to higher altitude?
- Arterial pressure of oxygen is higher
- Respiratory alkalosis (losing CO2)
- Renal compensation to reduce the excess bicarbonate to restore acid
- Kidneys also reduce volume, so less blood with more oxygen in it
- SV is down so HR needs to be up in order to get more oxygen into the blood
83
What is the effect on the cardiovascular system in the longer term response to high altitude?
- PV still down
- So SV still impaired because less blood coming back to the heart and your HRmax is lower as well
- Means decreased Qc in max exercise
- This all leads to increased red cell mass production (erythropoietin) which means you can restore aerobic power
84
What is the effect on the muscle in the longer term response to high altitude?
- Higher mitochondrial density
- Higher capillarisation
- Higher aerobic enzymes
- This all leads to increased red cell mass production (erythropoietin) which means you can restore aerobic power
85
When is acute mountain sickness common?
- Common during first several hours to days >3000m
- Directly related to speed of ascent and final altitude
- Partly genetic
- Aerobic fitness isn't protective
- Less common in females
86
What are the symptoms for acute mountain sickness?
- Severe headache
- Dizziness and dim vision
- Nausea, vomiting and constipation
- Insomnia and weakness
87
What are the causes of acute mountain sickness?
- Sub-clinical cerebral oedema due to high cerebral flow
- Cytotoxic injury to brain cells causing oedema
88
What is the prevention for acute mountain sickness?
- Gradual ascent
- High CHO diet and well hydrated
- Drugs (acetazolamide)
89
What is the treatment for acute mountain sickness?
- Time
- Drugs
- Oxygen or descent if severe
90
When is high altitude cerebral oedema common?
Not common (1%) but readily fatal if untreated
91
What are the symptoms for high altitude cerebral oedema?
- As for acute mountain sickness (AMS) (partly more severe though)
- Also, loss of motor control, poor reflexes, confusion
92
What are the causes, prevention and treatment for high altitude cerebral oedema?
The same as acute mountain sickness
93
When is high altitude pulmonary oedema common?
Not common (2%; males), but also potentially fatal
94
What are the symptoms for high altitude pulmonary oedema?
- Fatigue, dyspneoa, low SaO2, chest pain and tightness
- Persistent dry, irritating cough without phlegm
- Later: blood stained, frothy sputum and cyanosis
95
What are the causes for high altitude pulmonary oedema?
- Pulmonary hypertension
- Oxidative stress in lung (esp. from brain)
96
What is the prevetion for high altitude pulmonary oedema?
Unclear
97
What is the treatment for high altitude pulmonary oedema?
Assisted/stretchered descent
98
How should you prepare for high altitude climbing at >6000m?
- Cyclic exposure; repeatedly higher altitude
- Mostly, work high but sleep low
- Maladapt if continuously >6000m
99
How should you prepare for trekking at 2500-5000m?
- If arrive by plane, don't overdo PA/exercise
- Ascent and PA ideally gradual and cyclic
100
How should you prepare for competition at high altitude?
- 2100-2500m for >2 weeks
- Must drop training intensity
101
Does altitude training help performance at sea level?
Slight improvement, 1-4% but there is clearly much inter-individual difference
102
What is the threshold for erythropoietic response (EPO)?
2150-2450 for most people (wouldn't happen in NZ)
103
What might be the optimal method for altitude training and sea level performance?
- Live high (2100-2500m for >12h/day)
- Train high (2000-3000m for lower intensity)
- Train low (<1500m for high intensity sessions)
