W6 - Cold Exposure_Performance

Question 1

Describe the physiological responses to cold

Answer 1

In moderate cases, body shivers, using more energy. As this becomes more extreme the body switches from lipid to carbs

Question 2

How does wind affect exercise particularly in cold conditions and what one simple technique can be used to ↓ it’s effects?

Answer 2

Wind makes the difference—air currents on a windy day magnify heat loss because the warmer insulating air layer surrounding the body continually exchanges with cooler ambient air.
The wind-chill temperature index. If a person runs, skis, or skates into the wind, the effective cooling increases directly with forward velocity. Airway moisture loss during cold-weather physical activity contributes to mouth dryness, a burning sensation in the throat, irritation of the respiratory passages, and general dehydration. Wearing a mask that covers the nose and mouth and traps the water in exhaled air, and warms and moistens the next incoming breath, helps minimize this

Question 3

Explain the physiological responses to cold stress

Answer 3

Amount of subcutaneous fat and age

Question 4

Do humans adapt well to LT cold conditions?

Answer 4

Humans possess don’t cope as well to long-term cold exposure than to prolonged heat exposure. Eskimos have clothing and accommodation which helps them manage the cold challenges they face. The Ama women divers of S. Korea have a higher shivering threshold, possibly as a result of elevetaed resting metabolism.

Question 5

Review the evolutionary/ chronic adaptations to cold

Answer 5

With prolonged cold exposure 1. Shivering occurs at a lower body temperature because more heat is generated without shivering
2. Improved ability to sleep in the cold
3. Change in peripheral blood flow distribution that either
conserves heat in the core or warms the extremities to prevent cold injury LT 4. exposure can also reduce the immune response normally associated with acute cold exposure. 5. ↑ fitness also ehances defence against cold, producing a larger shivering response.

Question 6

What is the Heat Balance equation?

Answer 6

Metabolic Heat Production (M-W) = +-R (Radiation) +- K (Conduction) +- C (Convection) - E (Evaporation) = +- Heat Storage. All measured in Watts

Question 7

Why is insulated clothing often needed to cope with extreme cold?

Answer 7

Blood move to core, leaving limbs exposed to ambient temperature. Below certain temps damage occurs, hence why need to be insulated

Question 8

How are nerves affected by extreme cold?

Answer 8

Extreme cold, blood → core → lims exposed → tissue temperature falls. Below 20 degrees the condution of action potentials is slowed and their amplitude reduced. Between 5-15 degree all afferent pathways are blocked

Question 9

How easy is it to predict tissue temperature from skin temperature in hot & cold conditions?

Answer 9

Relatively easy in hot, not so in cold, where blood → core and what is left in the limbs can vary dramatically, and ∴ the skin temperature.

Question 10

How does falling tissue & skin temperature affect performance, mobility and dexteriity?

Answer 10

tissue temperatures ↓, ↓ performance, joint mobility. Skin temperature ↓, ↓ manual dexterity & tactile sensations

Question 11

When tissue temperature ↓ below 27 degree, muscle performance falls - by how much per 1 degree decrease?

Answer 11

3%

Question 12

Why does muscle performance fall below tissue temp of 27 degrees?

Answer 12

We think ∵ • Reduced enzymatic activity
• Slower ATP utilisation
• Slower diffusion rates (electrolytes, proteins, etc)
• Reduced muscle blood flow
• Increased viscosity
• Rate of nerve conduction decreased

Question 13

What happens to our CV system during cold exposure?

Answer 13

Vasocconstriction → ↑ blood pressure; NO is suppressed limiting vasodilation; both (I assume) contribute to cardiac hypertrophy → arrhythmias → stroke & heart attack

Question 14

What happens to our respiratory system during cold exposure?

Answer 14

Heat & moisture are drawn away, causing irritation to nasal passages, particularly with exercise. Putting a thin cloth across your mouth can ↓ this, and physiological adaptations can occur with chronic exposure. Can also → in bronchoconstriction (asthma). Nasal breathing can help.

Question 15

What two ways does the cold affect our ability to complete coninuous movement, what are the implicattions of them and what can be done to mitigate their effects?

Answer 15

1. Reduced cellular respiration (reduced metabolic processes)
2. Reduced tissue oxygenation (vasoconstriction)
   → Time to exhaustion is reduced.
   Therefore ↑ need for warm ups.

Question 16

How does the cold affect our performance, reference muscle force?

Answer 16

Reduced - Force generation depends on ability to contract quickly. Particularly relevant for Neuromuscular movements eg drop jumps, unless cold habituated.Therefore ↑ need for warm ups. There is a probably an optimum temperature. If the temp was very hot this ↑ the risk of heat exposure

Question 17

How does the cold water affect our O2 consumption?

Answer 17

Greater in cold water, therefore Earlier switch to anaerobic metabolism

Question 18

How does the cold affect our performance, reference swimming economy?

Answer 18

Reduced swimming efficiency and stroke length with progressive cold-water immersion. Note: Heat loss varies between people for a variety of reasons. Including varying amounts of adipose tissue; varying amounts of body area to weight ratios, a tall skinney person would probably lose heat quicker; plus a person’s ability to maintain their metabolic process (to offset the cold water). So assessments should be individualised

Question 19

How do we adapt to the cold?

Answer 19

a) hypermetabolic, b) insulative, and c) habituated responses. Hypermetabolic and/or insulative adaptations may occur after prolonged and severe cold exposures, resulting in enhanced cold defense mechanisms such as increased thermogenesis and peripheral vasoconstriction, respectively. Not seen that often as humans adapt via clothing buildings etc, but still seen with some indigenous people. Habituation occurs prior to these adaptations in response to short duration mild cold exposures, and, perhaps counterintuitively, elicits a reduction in cold defense mechanisms demonstrated through higher skin temperatures, attenuated shivering, and reduced cold sensations. These habituated responses likely serve to preserve peripheral tissue temperature and conserve energy during non-life threatening cold stress. In some countries this is conducted proactively (dipping children into freezing waters) as a protective mechanism to reduce accidental drowinings

Question 20

How do we adapt to water?

Answer 20

Repeated immersions reduced the heart rate,
respiratory frequency and volume responses. With hypothermia (long duation of exposure) - VO2 max decreases, but greater metabolic requirement with cold core temp in those individuals who aren’t acclimated

Question 21

Can cross adaptations occur?

Answer 21

General consensus is autonomic adaptations occur with altitude and cold exposure. • Adrenaline and noradrenaline < in second immersion (CW)
• Normally acutely increased with altitude exposure
• Symptoms of hypoxia reduced after cold
habituation in second exposure (CW)

Question 22

What is the benefit of brown adipose tissue for cold adaptation?

Answer 22

Generates heat quicker via non-shivering thermogenesis. Activated with very cold exposure via Uncoupling protein: thermogenin (→ ATP synthesis generating heat only). Found moreso in children but in Adults:
• Neck, supraclavicular, thoracic and
abdominal paraspinals.