Essentials of Nutrition for Sports

Athletes traveling to races commonly drink less because they
neglect to fill or bring waterbottles and are trapped in car or airplane seats.

You want not only your blood vessels to be hydrated, but your

cells to be filled as well. Consciously drink plenty of fluids and look for clear urine for several days before racing.

Look for Clear Urine

You generally know that your

blood

is well-hydrated when your

urine is clear. Two caveats: B vitamins may color the urine, and, conversely, clear urine does not guarantee that you are well-hydrated. Recent Studies

Urine color was found to be reliably correlated with percent

dehydration during a 30-mile mountain bike race that followed a pre-exercise hyperhydration protocol.

Does concentrated urine mean that one is not well-hydrated?

That is the common view. In fact, NCAA wrestlers cannot have their body composition measured for the wrestling season if specific gravity is >1.020. However, a study following well-hydrated volunteers found urine specific gravity was often more concentrated than that level.

Cell Dehydration

Lost blood fluid volume is quickly replaced by drinking water.

Cell dehydration, however, is different.

The cells of your body are mostly water. Fluid loss from the cells

may take many hours, or even a day or two, to replace. It is possible to experience cell dehydration, drink a lot, have clear urine, and still be dehydrated in the cells.

When you drink, the fluids travel from your gastrointestinal tract

into your bloodstream. The kidneys immediately sense the fullness

of the blood vessels and begin to eliminate what they perceive as surplus fluid. However, your cells may not have had time to absorb fluids and so remain dehydrated.

It is a little like a plant that has not been watered for some time.

The soil is dry, and the roots and leaves are dehydrated, so you water it. Before the plant can absorb

the water, it has run through the

porous, dry soil, leaving the plant leaves still dry.

Keep Fluids Handy

Having fluids readily available encourages drinking. Hydration backpack systems make sense in some sports.

Hydration systems can carry 100 ounces (3 quarts or liters), the equivalent of six standard waterbottles. They can be accessed more easily than waterbottles for some athletes, for example some mountain bikers or unskilled road riders. Recent Studies

Hydration backpack systems were associated with slightly better

hydration and performance than traditional frame-mounted bottles—in a mountain-bike study funded by CamelBak, a backpack hydration system.

Faster/Slower Hydration

Chilled and flavored fluids im

prove palatability and promote

hydration.

Studies have shown that both

sodium and carbohydrate improve

the rate of absorption of fluids from the gastrointestinal tract and reduce fluid losses in the urine.

Solutions with higher than 6% carbohydrate concentration may

delay stomach emptying, slow hydration, and cause gastrointestinal cramping. The hotter or more fatigued the athlete, the less the athlete is able to tolerate concentrated fluids.

Nutrition for Sports, Essentials of 29