When runners say that they hit the wall during long runs or races usually they
mean that they have to drop their pace significantly or even stop running. There
are essentially three walls:
- The inability of the muscle to run longer than certain distance. This happens
to newbies who have not trained enough to handle the distance. Consistent
long runs will eliminate this wall completely.
- Dehydration. This is the most common wall experienced by well trained runners.
It is caused by either poor hydration or the weather too hot for the hydration
to keep up with the body fluid loss. Some runners are more prone to dehydration
in hot weather than the others. The symptoms are numbness of hands, short
breath, muscle cramp, thirst, etc. When one feels thirsty at a race, it is
already too late to make up for it by any hydration process. Hydration process
for a marathon should start 48 to 72 hours before the race in such a way that
the urine is almost always kept clear.
- Hypoglycemia. This happens often among less trained eager runners whose
fat burning mechanism cannot keep up with their ambitious pace. The faster
the pace, the more contribution of energy is from carbohydrate and less from
fat. Less trained runners' carbohydrate/fat burning ratio is much higher than
well trained runners. The symptoms are dizziness, light-headedness and intense
craving for sweet. Consistent training will significantly elevate fat metabolic
rate during running and increase the glycogen store capacity so the glycogen
supply can last longer. This, in addition to proper carbo-load, can completely
eliminate the wall of hypoglycemia. Since the fat has much higher energy density
than the other two types of fuel - carbohydrate and protein, any healthy person
has enough fat to burn for almost any distance. There is no need to do fat-load
although there is a controversial study showing that fat-loading did help
a group of people to enhance their racing performance.
(Originally written on 10/27/02)
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