Nutrition: Hydration Strategy

2011-02-25

Keep Your Body Fluid!
Long-distance cycling during these hot summer days can lead to high sweat rates, and substantial water and electrolyte losses.  Due to the great variance in individual sweat rates; the impact of different sports and of the ambient temperature, it is impossible to come up with an expert ‘one-size fits-all’ hydration strategy for athletes.  Instead, there are sensible guidelines which can help the individual to become more aware and more responsive to their particular hydration needs.  It is a good idea to use your training regime to determine your hydration strategy for the Absa Cape Epic.

Hydration – balancing intake with loss:

§ Drink according to a plan, practice hydration strategies during training rides and reflect on what works best for you in particular conditions;

§ Before you start your ride or race make sure you are well-hydrated.  Drinking a carbohydrate-rich beverage, preferably one with electrolytes, several hours before the activity enables adequate fluid absorption. A rule of thumb is: taking in 5 – 7 ml per kg of body weight 1 – 4 hours prior to cycling. For a 70kg cyclist, this will mean consuming 420ml of carbohydrate drink or diluted juice 1 hour before the race.  Tweak this according to your own sweat rate, and consider the heat of the day.

§ The aim of hydration during exercise is to replace water and electrolytes lost through sweat.  It is important to be aware that your individual sweat rate differs not only in how much water you lose, but also how much electrolytes.  For instance, a person with a light sweat rate may still experience a high loss of electrolytes.  For this reason, a customized fluid replacement programme is highly recommended.  Individual sweat rates can be estimated by measuring body weight before and after exercise; and replacing fluid accordingly. One kilogram of body weight lost is roughly equal to one litre of water lost.  Use this measurement and tailor it to your needs to determine how much fluids you should drink while you are cycling.

§ After exercise, the goal is to replace fluid and electrolyte losses. Quantities will differ from individual to individual - but some sources recommend 450 – 675 ml of carbohydrate and electrolyte-rich fluid per 0.5 kg weight loss. Note that you will continue to lose sweat for some time after exercising.  So when it comes to actually riding the Absa Cape Epic make sure you continue your rehydrating regime after each day’s race.

 What are electrolytes?

Electrolyte is a "medical/scientific" term for salts, specifically ions - such as sodium, potassium, or chloride, required by cells to regulate the electric charge and flow of water molecules across the cell membrane. Electrolytes are important because they are what your cells (especially nerve, heart and muscle cells) use to maintain voltages across their cell membranes and to carry electrical impulses (nerve impulses, muscle contractions) across themselves and to other cells.

Is there an ‘Ideal’ Sports Drink?

Of course, there is always lots of debate about the possibilities of an ’ideal’ sports drink.  What is important is to understand the contents and the roles they play in restoring healthy hydration.  A suitable rehydration beverage for athletes should contain an readily available carbohydrate and electrolytes.  Small amounts of an easily absorbed protein can further enhance recovery, and is important during stage racing.  Vitamin C and polyphenols (found in fruit juice) can enhance a drink’s nutritional value as they assist the body’s immune function.

The amount of carbohydrate in the drink can be varied according to individual needs and environmental conditions. A carbohydrate intake of 30 - 60g per hour, or concentration of less than 10% will be of benefit. If the concentration of a drink is too high it can lead to diarrhoea or gastric discomfort.  Research (and experience!) has also shown that a more diluted solution of 4% carbohydrate (containing electrolytes like Rehydrat) is best tolerated in extremely hot conditions. 

Choose a drink that contains a combination of sugars (glucose, glucose polymers, sucrose and fructose). Glucose polymers (maltodexrin) can provide up to 10 times the energy of simple sugars for the same osmolality* without leading to gastric discomfort.  Fruit juice can be used as a recovery drink, but has a high fructose concentration that may lead to gastric discomfort if used in excess. If you cycle on juice, rotate with another energy drink or dilute down with water and add electrolytes.  

*Osmolality is the measure of the number of particles in a solution (concentration)

What about Caffeine?

Small amounts of caffeine enhance power during the final hour of prolonged exercise. Latest research shows that coffee will not lead to or exasperate dehydration. In some individuals, it can lead to gastric discomfort – so be careful of using caffeine if you have a sensitive stomach.

Alcohol

Since alcohol can act as a diuretic (particularly at high doses) and increase urine output, it should be consumed in moderation, particularly during the post-exercise period.  Alcohol also reduces glycogen storage; and due to its vasodilatory affect, there is an increased risk of bleeding and swelling - all affecting recovery rate.

Can I drink too much?

Exercise-associated hyponatremia(low blood sodium levels)  was first reported at the Comrades Marathon, and it subsequently was regarded as a particular risk for endurance runners. However, since then there have been a number of reports of participants suffering from hyponatremia during a variety of occupational and recreational activities who were hospitalized, with several having died.   Nowadays it is accepted that hyponatremia can occur during any ultra-endurance event that lasts longer than four hours.  The condition is a result of over-consumption of fluids that exceeds sweating rate.  The risk is increased by especially consuming fluids that do not contain the necessary electrolytes.

Avoid over-hydration by:

• Being aware of and responding appropriately to your thirst
• § Ensuring adequate electrolyte intake from drinks (either from a sport drink or by adding additional electrolytes to diluted drinks or water)
• § Eat salty snacks on long rides – such as biltong, pretzels, salted potatoes or marmite sandwiches
• § Be aware that non-steroidal anti-inflammatory drugs and pain relievers can contribute to developing water overload

Beating the heat – Exercising in hot weather

Vigorous exercise in hot weather can put some people at risk of heat illness.  If untreated, heat illness can lead to the more serious and potentially life-threatening condition of heat stroke. The following guidelines and tips from Sports Medicine Australia will help you to spot the signs of heat illness and take the necessary measures to prevent it!

Remember: Dehydration and heat stress = poor performance

How do you tell if someone has heat illness?

Heat illness can occur during strenuous sports, and especially in hot weather.  During sports activities participants should “listen to their bodies”. If you or your partner start to experience any of the following symptoms or signs, stop riding immediately.

Symptoms of heat illness may include:

§ light headedness, dizziness

§ nausea,

§ obvious fatigue

§ cessation of sweating

§ obvious loss of skill and coordination/clumsiness or unsteadiness

§ confusion

§ aggressive or irrational behaviour

§ altered consciousness

§ ashen grey pale skin

Heat Exhaustion or Heat Stroke?

Heat illness in sport presents as heat exhaustion or heat stroke. Heat exhaustion is the more common sports-related heat illness. Heat stroke is rare, but it is a life threatening condition.

Heat exhaustion: Participants who collapse after exercise are likely suffering from a post-exercise drop in blood pressure (postural hypotension), but some may have heat stroke.

Heat stroke: Those who show signs of altered mental function, loss of consciousness or collapse during exercise are likely suffering heat stroke.

Sports participants showing signs of confusion, loss of skill, loss of coordination or irrational behaviour should be stopped and assisted immediately.