CH.14

What would you tell an endurance athlete concerning the intake of fluids (including sugar) before and during competition?

Hyrdrate properly before exercises (5-7 ml per kg pf body weight an hour prior) and small salt snacks. During exercise, replace fluid to maintain less than a 2% loss of body weight in sweat.

Define hyponatraemia.

If you consume too much water you can dilute your blood sodium to fatally low levels. Can also happen when you don't drink enough water causing dehydration and salt loss due to sweating.

What is relative humidity?

A ratio expressed as a percentage of the amount of water vapour in the air to the amount of water vapour the air could hold at the same temperature if saturated. 100% humidity means the air is completely saturated with water vapour.

Compare conduction and convection as methods of heat loss.

Conduction: The transfer of heat between two objects in direct contact. The direction of heat is always from warmer to the cooler object. Body heat is transported by blood circulation to the surface through the tissues. Convection: the transfer of heat between the surface of the body and the air (or water) bc of the circulation of air molecules next to the skin. More air movement= more heat loss.

List two physiological mechanisms humans use to cool the body in hot environments

Evaporation (sweating), vasodilation.

Describe physiological adaptations to exercise in the heat that occur with repeated exposures to exercise and thermal stress.

Heat acclimation improves general tolerance to heat. Plasma volume and total body water increased, cardiac output better distributed between skin and working muscles.

Do you agree or disagree with the following statement: "If you are participating in a vigorous sport in hot weather, you should change your uniform when it becomes wet from sweat." Explain.

No, since effective evaporation can only occur when the clothing becomes wet throughout and reduces the chance of cooling effects form evaporation. You will have to soak the clothing again in order to regulate the temperature.

Give a physiological explanation of why it is more difficult to perform strenuous exercise in the heat than in normal temperature conditions.

Puts additional stress on the circulatory system bc it has to supply a large blood flow to the working muscles and to the skin In order to dissipate heat. Sweat loss reduces blood volume adding further stress.

Is it possible to drink too much during an athletic event? Explain the physiological reasons for your answer.

Yes, there is a maximum amount of fluid that can be absorbed from the stomach during exercise. Ranges between 200-800ml/hour of exercises and depends on the body mass and intensity of the exercise.

If you were a football coach in a warm climate, describe the advice that you would give to your players regarding drinking guidelines and clothing in order to decrease the probability of heat-stress disorders.

Stay well hydrated and replenish electrolytes. Remove as much clothing as possible during rest periods and remove helmets when feasible.

Describe two methods that can be used to assess environmental heat stress.

The wet-bulb globe temperature test and using a heat index.

List two processes that they use to maintain body temperature in cold environments.

Vasoconstriction, increased heat production from metabolism.

Explain why there is a much greater risk of heat illness in humid weather than in dry weather.

When the relative humidity is high on a hot day and you're producing heat at a high rate while exercising, temperature regulation may be extremely difficult. When you sweat it won't evaporate on the surface of the skin thus no cooling effect.

Define dipsomania.

When you ingest too much fluid causing over-hydration can cause the body and the brain to swell. Can lead to convulsions, heart failure, and cessation of breathing. Also called "water intoxication"

Is it necessary to ingest electrolyte replacement drinks during exercise in the heat?

Yes especially in prolonged events in hot environments. Salt and minerals help with maintaining proper body functions/work rate.