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PDEP > W7 - Hot/Humid Environments > Flashcards

W7 - Hot/Humid Environments Flashcards

1
Q

How important might ambient temperature be to endurance performance?

A

Very.

Many studies show athletes in a hot env can do less exercise compared to in a cooler env.

If exercise is occurring at a higher temp then athletes will tire quicker + it will -ively impact performance.

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2
Q

Temperature for normothermia

A

36.5-37.5 degrees celcius

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3
Q

What is hyperthermia

A

1 degree Celsius increase in our normal core temp.

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4
Q

What is the most important mechanism of heat loss during exercise?

A

Evaporation

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5
Q

When does sweating only cool you down?

A

When it evaporates off the skin.

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6
Q

What must be homeostatic ally controlled?

A

Core temp

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7
Q

When is core temp its highest?

A

Afternoon

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8
Q

Literature link to oeseophageal temp

A

Despite different oesophageal temperatures at the start, all participants reached exhaustion at oesophageal temperatures 40.1-40.2 celsius

(Gonazles-Alonzo et al, 1999)

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9
Q

What has been revealed to be the optimum temp for endurance performance until exhaustion and by who?

A

11 degrees celcius

Galloway & Maughan 1997

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10
Q

What has been revealed to be the optimum temp for endurance performance for those who are the top 25% in their fields until exhaustion and by who?

A

women - 10.

men - 7.

Helou et al, 2012

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11
Q

Data for the finishers of the Olympic marathon from 1896-2000

A

<25 celsius = 79% of runners finished

> 25 celsius = 54% of runners finished

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12
Q

Are sweat losses usually a limiting factor during exercise?

A

NO

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13
Q

Sweat losses of ~2 and ~3 %

A

~2% bodyweight can impair prolonged endurance performance.

~3% may elicit impairments in cognitive function.

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14
Q

What does passive raising of core temp reduce?

A

Voluntary activation

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15
Q

What is associated to drowsiness?

A

Increase in alpha and beta brainwaves.

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16
Q

When is global cerebral oxygenation likely to be impaired?

A

When CBF is reduced beyond 50%

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17
Q

What has a dependent effect of. muscle temp on peak power output?

A

Velocity

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18
Q

Improving performance in the heat…

Effective interventions can be carried out in the days before (chronic) or on the day of + during (acute) heat exposure + 1 will achieve 1 or + of the following…

A

Increased or maintained heat dissipation

Reduced initial body heat

Altered thermal perception.

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19
Q

Acclimation vs acclimatisation

A

Acclimation - Laboratory

Acclimatisation - Natural env.

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20
Q

What has reduced initial deep-body temp + increased heat dissipation rates?

A

Acclimation and/or acclimatisation to heat

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21
Q

What is the benefit to acclimation or acclimatisation to the heat?

A

Reduces thermal-strain for a given external work-rate during exercise in a thermally stressful env.

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22
Q

How is heat acclimatisation/acclimation achieved?

A

By repeatedly elevating deep-body and skin temp to a high level that elicits pronounced sweating.

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23
Q

Active approaches of acclimatisation/acclimation

A

Exercise in a hot+/or humid env

Exercise in clothing restricting heat loss.

24
Q

Passive approaches of acclimatisation/acclimation

A

Hot baths can be effective

25
Q

Which are more effective for acclimatisaiton/acclimation?

Longer or shorter exposures?

A

Longer i.e ~10 daily exposures rather than ~5

26
Q

Sex differences for the rates of acclimatisation/acclimation?

A

Adaptation may be slower in females

27
Q

Acclimation/Acclimatisation

What is a common target temperature for the deep-body to reach?

A

~38.5

Higher temps could increase heat-illness risk.

28
Q

How long is heat acclimation/acclimatisation retained for?

A

At least 7 days

Any benefits that are lost within a month are re-acquired with 2-4 further exposures.

29
Q

What comes under acute interventions

A

Hydration

Pre + per cooling

Perceptual manipulation

30
Q

Strategy for the acute hydration intervention

A

Ensure euhydration prior to exercise

Prevent excessive dehydration thereafter.

31
Q

Strengths to the acute hydration intervention

A

Helps maintain thermoregulatory capability

Cost-effective

32
Q

Weaknesses to the acute hydration intervention

A

Practically/logistically difficult in some situations.

Palatability/tolerance may affect ingestion rate.

33
Q

Strategy for the acute pre/per-cooling intervention

A

External i.e cool water immersion + cooling garments.

Internal i.e cool-liquid ingestion

Mixed-methdos

34
Q

Strengths for the pre/per-cooling acute intervention

A

Reduced initial body heat content +/or creates heat sink.

Effective when evaporation is compromised

Cost-effective

35
Q

Weaknesses for the pre/per-cooling acute intervention

A

Can be logistically difficult.

Deep-body temp monitoring required for pre-cooling.

Cooling garment efficacy influenced by env.

36
Q

Strategy of acute perceptual manipulations

A

L-menthol application

Local cooling

37
Q

Strengths to the acute perceptual manipulations intervention

A

Cost - effective

Reduced perception of hotness.

38
Q

Weakness to the acute perceptual manipulations intervention

A

Little/no effect on thermal state.

Potentially dangerous as may enable high deep-body temps.

39
Q

By how much does pre-cooling aim to reduce deep-body temp?

A

By ~0.5-1 degree

Enabling greater heat storage before hyperthermia develops.

40
Q

What does decreased muscle and skin temp cause?

A

Cutaneous vasoconstriction

Diverts blood from active tissues + slows nerve conduction + muscle contraction with can cause initial feelings of ‘sluggishness’.

41
Q

Exercise in the heat is associated with a thermoregulatory burden mediating what

A

CV challenges

Influencing cerebral function

Increases pulmonary ventilation

Alters muscle metabolism

42
Q

What is performance clearly impaired by for max intensity exercise in the heat?

A

CV limitations to support both the thermoregulation and O2 delivery to the active skeletal muscle at the same time.

43
Q

What does central fatigue during exercise in the heat appear to be influenced by?

A

NT activity of the dopaminergic system.

44
Q

Define heat stress

A

Refers to the env exercise conditions that elevate body temp

45
Q

Define heat strain

A

Refers to the physiological consequences of heat stress.

46
Q

What is the magnitude of stress + the resulting strain dependent on the complex interaction of during exercise in the heat?

A

Env factors i.e ambient temp, humidity, clothing worn…

Ind biological characteristics i.e heat acclimatisation status, aerobic fitness + body size.

Exercise task i.e metabolic rate + duration

47
Q

The greater the heat stress…

A

The greater the impaired aerobic exercise performance.

Heat acclimatisation moderates these performance impairments, dehydration accentuates them.

48
Q

When will the core-to-skin temp gradient be narrower

A

In warm-hot env than cool-temp env.

49
Q

Reductions in renal and gastrointestinal bf in combination with peripheral venonconstricition may benefit the….

A

Translocation of blood to the central circulation + help sustain cardiac filling during exercise-heat stress.

50
Q

What may happen if gut perfusion is insufficient for a prolonged period during exercise in the heat?

A

It can act to impair aerobic perf by reducing water + substrate uptake from the gut + provoke endotoxin leakage.

51
Q

What has endotoxin leakage been recognised to contribute to?

A

Heat stroke

52
Q

When is impairment to aerobic exercise capacity due to increased heat stress present?

A

During moderate + high intensity exercise.

May emerge as lower power output or speed during TT or reduced TTE during exercise w/ a fixed workload.

53
Q

What remains unclear surrounding dopamine levels and hyperthermia?

A

Remains unclear is low dopamine levels are involved in the central fatigue associated with hyperthermia.

54
Q

What presents as a major challenge to the elite marathon runner?

A

Combination of high temp + high humidity.

55
Q

Sweat evaporation limits the rise in core temp but dehydration will…

A

Impair CV function

= Fall in bf to muscle, skin + other tissues.

56
Q

What is the rate of heat production in runners determined by?

A

Roughly proportional to running speed + body mass.

Also depends on ind running economy.

57
Q

Where do faster runners perform at of their aerobic capacity?

A

Faster runners perform at a higher fraction of their aerobic capacity

(Maughan & Leiper, 1983)

PDEP (7 decks)

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