Marathon, 26.2-mile race, could be daunting
experience for athletes.
One common medical conditions that come
across during recent marathon is Dilutional hyponatremia.
Elite athletes are less likely to develop
significant dehydration or over-hydration, and tend to drink less during
marathons. They tend to finish slightly dehydrated (ie; 1 -2% ), which showed
to be beneficial. Their fluid recommendations are geared toward providing
sufficient energy for fast-paced running.
The longer a runner takes to finish, the
greater risk of coming to harm from over-hydration.
Aim – To finish the race having neither gained weight through over
hydration nor lost more than 2-3% of starting weight.
Sports
drinks contain fluid, Carbohydrate and
electrolytes. Athlete can add more glucose, sugar and salt to become their
favored drink that suited their personal needs.
Fluid
intake should begin from the start of the marathon
and continue at a rate of 400 - 600ml of fluid per hour during
competitive running. Preferably drink
according to thirst, but not to drink according to weight loss.
Carbohydrate should be provided in the form of glucose mixed with other sugars,
including sucrose and glucose polymers to aid absorption, intake should be at a
rate of 30-60 grams per hour. High carbohydrate concentration of CHO can
impair absorption form the stomach and may cause stomach upset.
Electrolytes such as sodium, potassium and lost in the sweat, need to be replaced as well. Drinks should have 10-70mmol/L (average 30mmol/L) of Sodium and 2-5mmol/L of Potassium to match sweat losses.
Caffeine (roughly 2 cups of coffee) at least one hour before the
start of the race, can help mobilizing alternative fuels, has a CHO sparing
effect, and may facilitate absorption of glucose in the intestine.
To calculate own estimate sweat rate –
Weight naked, run 1 hr and when return, dry all the sweat with a towel and weigh
again. Difference between the two is
hourly sweating rate.
Usually replace 50-80% of this
amount per hour during marathon, since the body makes water as by produce of
burning fuel.
Recipe
for Average sports drink
Juice crused from one orage (provides
flavor and potassium)
Make up to 1 L water
30mmol of Sodium (1.74gm salt)(1/2 to one
teaspoon)
30gm of glucose powder/sugar mixture
mix well
Reference: Marathon medicine by Dr. L
Creaney and Dr. P Dijkstra