W7 - Hot/Humid Environments

Question 1

How important might ambient temperature be to endurance performance?

Answer 1

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.

Question 2

Temperature for normothermia

Answer 2

36.5-37.5 degrees celcius

Question 3

What is hyperthermia

Answer 3

1 degree Celsius increase in our normal core temp.

Question 4

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

Answer 4

Evaporation

Question 5

When does sweating only cool you down?

Answer 5

When it evaporates off the skin.

Question 6

What must be homeostatic ally controlled?

Answer 6

Core temp

Question 7

When is core temp its highest?

Answer 7

Afternoon

Question 8

Literature link to oeseophageal temp

Answer 8

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

(Gonazles-Alonzo et al, 1999)

Question 9

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

Answer 9

11 degrees celcius

Galloway & Maughan 1997

Question 10

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?

Answer 10

women - 10.

men - 7.

Helou et al, 2012

Question 11

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

Answer 11

<25 celsius = 79% of runners finished

> 25 celsius = 54% of runners finished

Question 12

Are sweat losses usually a limiting factor during exercise?

Answer 12

NO

Question 13

Sweat losses of ~2 and ~3 %

Answer 13

~2% bodyweight can impair prolonged endurance performance.

~3% may elicit impairments in cognitive function.

Question 14

What does passive raising of core temp reduce?

Answer 14

Voluntary activation

Question 15

What is associated to drowsiness?

Answer 15

Increase in alpha and beta brainwaves.

Question 16

When is global cerebral oxygenation likely to be impaired?

Answer 16

When CBF is reduced beyond 50%

Question 17

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

Answer 17

Velocity

Question 18

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…

Answer 18

Increased or maintained heat dissipation

Reduced initial body heat

Altered thermal perception.

Question 19

Acclimation vs acclimatisation

Answer 19

Acclimation - Laboratory

Acclimatisation - Natural env.

Question 20

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

Answer 20

Acclimation and/or acclimatisation to heat

Question 21

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

Answer 21

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

Question 22

How is heat acclimatisation/acclimation achieved?

Answer 22

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

Question 23

Active approaches of acclimatisation/acclimation

Answer 23

Exercise in a hot+/or humid env

Exercise in clothing restricting heat loss.

Question 24

Passive approaches of acclimatisation/acclimation

Answer 24

Hot baths can be effective

Question 25

Which are more effective for acclimatisaiton/acclimation? Longer or shorter exposures?

Answer 25

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

Question 26

Sex differences for the rates of acclimatisation/acclimation?

Answer 26

Adaptation may be slower in females

Question 27

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

Answer 27

~38.5 Higher temps could increase heat-illness risk.

Question 28

How long is heat acclimation/acclimatisation retained for?

Answer 28

At least 7 days Any benefits that are lost within a month are re-acquired with 2-4 further exposures.

Question 29

What comes under acute interventions

Answer 29

Hydration Pre + per cooling Perceptual manipulation

Question 30

Strategy for the acute hydration intervention

Answer 30

Ensure euhydration prior to exercise Prevent excessive dehydration thereafter.

Question 31

Strengths to the acute hydration intervention

Answer 31

Helps maintain thermoregulatory capability Cost-effective

Question 32

Weaknesses to the acute hydration intervention

Answer 32

Practically/logistically difficult in some situations. Palatability/tolerance may affect ingestion rate.

Question 33

Strategy for the acute pre/per-cooling intervention

Answer 33

External i.e cool water immersion + cooling garments. Internal i.e cool-liquid ingestion Mixed-methdos

Question 34

Strengths for the pre/per-cooling acute intervention

Answer 34

Reduced initial body heat content +/or creates heat sink. Effective when evaporation is compromised Cost-effective

Question 35

Weaknesses for the pre/per-cooling acute intervention

Answer 35

Can be logistically difficult. Deep-body temp monitoring required for pre-cooling. Cooling garment efficacy influenced by env.

Question 36

Strategy of acute perceptual manipulations

Answer 36

L-menthol application Local cooling

Question 37

Strengths to the acute perceptual manipulations intervention

Answer 37

Cost - effective Reduced perception of hotness.

Question 38

Weakness to the acute perceptual manipulations intervention

Answer 38

Little/no effect on thermal state. Potentially dangerous as may enable high deep-body temps.

Question 39

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

Answer 39

By ~0.5-1 degree Enabling greater heat storage before hyperthermia develops.

Question 40

What does decreased muscle and skin temp cause?

Answer 40

Cutaneous vasoconstriction Diverts blood from active tissues + slows nerve conduction + muscle contraction with can cause initial feelings of 'sluggishness'.

Question 41

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

Answer 41

CV challenges Influencing cerebral function Increases pulmonary ventilation Alters muscle metabolism

Question 42

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

Answer 42

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

Question 43

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

Answer 43

NT activity of the dopaminergic system.

Question 44

Define heat stress

Answer 44

Refers to the env exercise conditions that elevate body temp

Question 45

Define heat strain

Answer 45

Refers to the physiological consequences of heat stress.

Question 46

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

Answer 46

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

Question 47

The greater the heat stress...

Answer 47

The greater the impaired aerobic exercise performance. Heat acclimatisation moderates these performance impairments, dehydration accentuates them.

Question 48

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

Answer 48

In warm-hot env than cool-temp env.

Question 49

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

Answer 49

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

Question 50

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

Answer 50

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

Question 51

What has endotoxin leakage been recognised to contribute to?

Answer 51

Heat stroke

Question 52

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

Answer 52

During moderate + high intensity exercise. May emerge as lower power output or speed during TT or reduced TTE during exercise w/ a fixed workload.

Question 53

What remains unclear surrounding dopamine levels and hyperthermia?

Answer 53

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

Question 54

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

Answer 54

Combination of high temp + high humidity.

Question 55

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

Answer 55

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

Question 56

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

Answer 56

Roughly proportional to running speed + body mass. Also depends on ind running economy.

Question 57

Where do faster runners perform at of their aerobic capacity?

Answer 57

Faster runners perform at a higher fraction of their aerobic capacity (Maughan & Leiper, 1983)