Overview

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• Overview
• Water Balance and regulation
• Gastric emptying revisit
• Dehydration performance
• CHO
• Hyponatremia
• Sweat rates
• Guidelines

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Gastric emptying

• INGESTION
• STOMACH
• SMALL INTESTINE
• BLOOD
• ABSORBED

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Factors affecting gastric emptying

• Temperature
• Acidity of the food
• High intensity exercise
• Dehydration
• Solid versus liquid
• Stomach volume

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Osmolality

• Refers to the concentration of particles in
  solution.

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CHO Electrolyte content
Drink CHO Na K Cl
Osmo
CHO g/L Electrolytes in mmol/L Osmo in mosmol/kg
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Hyponatremia

• Low plasma sodium conc.
• Noakes claimed due to water intoxification
• Hiller found also occurred in dehydration cases
• Can cause epilepsy, syncope, loss in performance,
  neural failure

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CHO replacement

• Amount
• Frequency
• Solid v Liquid
• Glycaemic index
• Palatability

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Sweat losses

• Weigh in minimal clothing before and after and
  check difference
• Fluid intake - water bottle before and after
• Urine losses change in body mass before and after

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Calculations

• Sweat loss change in mass (g) fluid intake (ml
  or g) - urine losses (g)
• Sweat rate (ml/h) sweat loss / duration of
  exercise
• Fluid deficit change in mass
• dehydration change in mass / pre- exercise
  body mass.

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Example

• A rider weighs in 0.5kg less following a training
  session
• There is half a 500mL bottle left out of 2
• After visiting the toilet they are 0.1kg lighter

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Example

• Sweat loss 500 750-1001150
• Sweat rate 1150 / 1.5 766 mL/h
• Fluid deficit 500mL
• dehydration (0.5 / 70) 100 0.7

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Guidelines for fluid / CHO intake during exercise

• Refuel and rehydrate to a plan ( and a back up
  plan)
• Weight loss is temporary fluid loss
• Cannot toughen to dehydration
• Practice rehydration
• Individualise
• Calculate sweat losses

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• Prime stomach to enhance GI emptying
• Top up regularly 10-15 min is ideal
• Complete replacement during if possible
• During performance 50-80 g per hr CHO

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Checklist

• Can you measure temperature and humidity
• Monitor heart rate
• Are the scales accurate and reliable
• What type of drink will you use (CHO/H20)
• Palatability
• Who is prone to heat stress
• Experience of athletes in the heat
• Clothing, sun block
• Electrolytes