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When
designing a nutritional program to supplement the body's energy
stores, the rate of digestion and absorption of foods must be
taken into account. The time needed for the stomach to start the
digestive process, empty its contents into the small intestine,
and have the food components absorbed into the bloodstream will
directly affect how quickly any food will be available to the
muscle to provide the Calories for exercise.
You
have some control over four major factors influencing the digestive
process.
- Solid
versus liquid -
liquids are emptied from the stomach more quickly than solids.
- Fat
content of the food
- fat slows the digestive process and delays the availability
of any Calories to the muscles.
- Sugar
concentration -
especially in liquids, a sugar content of more than 10% will
slow stomach emptying. (The use of complex carbohydrates,
will offset this to some degree and offers an alternative
strategy to maximize Caloric intake.)
- Physical
activity level of the cyclist
- the mechanical activity of digestion is slowed by any vigorous
activity, usually starting at 70% VO2 max. Except in short,
all out events, this is rarely an issue, and it is much less
so for cycling than for running where the additional component
of mechanical stimulation of abdominal contents from the sport
itself slows digestive tract functioning.
From
the above four points, it is easy to see that the optimal food
for a rapid, high energy boost during a ride would be a semi-liquid
or liquid carbohydrate with minimal if any fat. On the other hand,
an endurance athlete, competing at a lower VO2 max., might prefer
a complex carbohydrate with some fat added to improve taste (and
generally in a solid form), in order to slow emptying from the
stomach and even out absorption over a longer period of time.
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