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