CPTIPS Nutritional Program

Energy and Cycling

Designing a nutritional program requires an understanding the relationship between energy production to support muscle contractions and the energy requirements of cycling.

Energy is produced by the metabolism (oxidation) of the food we eat (O2 + food). Oxidation provides a high energy molecule, ATP which then powers muscle contractions.

PHYSIOLOGY OF METABOLISM (more detailed discussion)


Energy is stored in the body in fats, carbohydrates, and protein. Except in malnourished states, protein is not used as an energy source. From this point on, the discussion will be referring to CHO and fats.

This energy is released through a chemical reaction with oxygen in a process called oxidation. When oxidation occurs outside the body - for example the burning of oil (a fat) in a lamp or the use of a flaming sugar cube (a carbohydrate) as a decoration in a dessert - this energy is released as heat and light. In the body however, food energy needs to be released more slowly and in a form that can be harnessed for basic cell functions and transformed into mechanical movement by the muscle cells.

Oxidation results in the formation of a single chemical compound adenosine triphosphate (ATP). It is this ATP, synthesized as the cell metabolizes (or breaks down) these three basic foods, that transfers the energy content of all foods into muscle action.

Metabolism can be aerobic or anaerobic.

So you can see that adequate oxygen is necessary to optimally use your fuel reserves. That is why cardiac physiology is so important in understanding metabolism.

CARDIOVASCULAR PHYSIOLOGY (more detailed discussion)


At levels of exertion greater than the VO2 max., the energy requirements of the cells outstrip the ability of the cardiovascular system to deliver the oxygen required for aerobic metabolism to the individual muscle cells, and oxygen independent or anaerobic energy production begins. Anaerobic metabolism is not only less efficient, with a more rapid depletion of muscle glycogen stores, but also results in a build up of lactic acid and other metabolites that ultimately limit performance even when adequate glycogen stores remain. This lactic acid is metabolized AFTER exercise levels decrease and excess oxygen is again available to the muscle cell. It's degradation is responsible for the oxygen debt or recovery phase that follows anaerobic exercise.

ENERGY REQUIREMENTS OF CYCLING (more detailed discussion)

Work, measured in Watts or Calories, is done as one cycles.

At cycling speeds greater than 15 mph, the energy needed to overcome AIR RESISTANCE greatly exceed those of the rolling and mechanical resistance in your bike. For example, in going from 7.5 mph to 20 mph: The number of Calories needed for any ride can be calculated - avg. speed of the ride x the time of the ride. Assuming:

the following is a good estimate for replacement Caloric needs for the exercise:

For a more detailed discussion of Caloric needs of cycling, go to THE CALORIC EXPENDITURE OF EXERCISE

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