Hydration

Fluid – the forgotten nutrient Humans contain 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 ~ mls/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 mls every 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