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Hydration
Fluid – the forgotten nutrient
•Humans contain 30-50 litres of water.•We lose water through sweat, urine and
evaporation.•Water turn over varies between athletes.•Turnover increases during exercise and
hot conditions.
Effects of Dehydration
•Impaired Performance▫By 10-20% with ~2% of body weight
•Impaired Mental Function▫Slowing reaction-response times▫Decision making skills
•Increased risk of heat cramps, exhaustion and stroke▫>3% fluid loss
Monitoring Hydration
•Urine Colour chart
Monitoring Hydration cont...
•Hydration Monitor – Refractomer
•Weight Flactuation – Before and after exercise▫E.g. Athlete consumed 1L fluid during
exercise but lost 1kg in weight from sweating.
▫Total sweat loss = 2L
Case Study - Mark
•Mark is a central forward•Participates in a high intensity 90minute
soccer training session•Pre-training weight = 75kg•Drinks 1.5L during training•Post-training weight = 73kg•To avoid dehydration and over-hydration,
how much fluid should Mark consume during his next training session?
Case Study - Mark• Weight loss = 75-73kg = 2kg (~2L)• % weight loss = 2/75kg= 2.7% (dehydrated)• Total sweat loss = 2L weight loss + 1.5L drank during
training = 3.5L• Allowable sweat loss = 2% x 75kg= 1.5L• Minimum fluid replacement = 3.5 – 1.5L =
= 2L over 90 mins=~300mls per 15 minutes
• Maximum fluid replacement = 3.5L= 3L over 90 minutes= 450mls per 15 minutes
• Recommended Intake for Mark~ 300-450mls/15min
What type of Fluids?
Drink water if•Exercise <30 minutes•Low intensity exercise•If high intensity > 30-60mins and cannot
tolerate sports drinks– need to take CHO and sodium in another form
Sports Drinks
•Provide:▫Carbohydrate for extra energy▫Fluid for hydration▫Electrolytes e.g. sodium
•Choose according to requirement for:▫ Fluid▫Carbohydrate▫Fluid and carbohydrate▫Electrolytes
Hypotonic Sports Drinks
•Contain less than 6g CHO/100ml•Used when wanting to replace more fluid
than CHO•Can be beneficial in hot climate with little
physical activity.
Isotonic Sports Drinks
•Contain 6-8g CHO/100ml•Used when wanting to replace fluids and
CHO equally•Generally most effective choice in most
situations. E.g. Team sports and individual sports.
Hypertonic Sports Drinks
•Contain more than 8g CHO/100ml •Used when wanting to replace more CHO
than fluid.•Suitable for cold climates where
dehydration is not a problem but large energy expenditure. E.g. Cross country skiing, Mountaineering.
What affects fluid intake?
•Athletes awareness of their sweat losses•Awareness of disadvantages of
dehydration•Dislikes taste/sensation• Availability of fluid•Stomach comfort•Fear of weight gain•Fear of need to urinate during exercise•Lack of practice
Developing a Fluid Plan
Pre Exercise/Event•Well hydrated before exercise
▫Drink fluids regularly throughout the day leading up to training/event
▫Have drink with meals and snacks•Fluid choice
▫ Any fluid during the day to make up 2L and meet CHO requirements
▫ Isotonic/Hypotonic/water in 1-2h prior to training/event
Developing a Fluid Plan
During Exercise/Event• Fluid choice
▫ Generally isotonic▫ If cannot tolerate – hypotonic/water &
CHO food•150-200mls every 10-15 minutes as a
guide but really should match individual athletes sweat loss
•Depends on practicalities of your sport•Practice fluid replacement plan in training
Developing a Fluid Plan
Post Exercise/Event•Fluid choice
▫Generally Isotonic▫If cannot tolerate then hypotonic/water
plus CHO foods with salt•1 kg body weight lost = 1L fluid loss•Aim to drink 1.5 x fluid loss over 2-4hrs
after event