The concept of calories in food is everywhere. Visit any bookstore and the section of the building that contains books on dieting and calories is among the largest you will find. It seems so simple: eat fewer calories then one uses each day and body weight will be lost. Consume more calories then is used each day and body weight will be gained. Calories are scientific units of measurement that are used both in energy intake and energy expenditure by animals. But, what really are the calories importance to a middle distance runner and their training and racing? The everyday use of the term calories is a means to indicate potential energy in the foods that are available for consumption. In actuality, foods are measured in kilo-calories (KCAL) or one thousand calories per Calorie. This is a scientific unit of measurement. Running the mile uses energy and this use can be measured in calories as well. This would be energy expenditure.
There are no such things as “good” calories or “bad” calories in food. Yes, there is an association that high calorie food has fewer vitamins and minerals, and lower calorie food contains more water, but a calorie is just a scientific unit of measurement like a Celsius degree on a thermometer. The higher the calorie content the more potential energy in food, while the lower the calories the lower the energy potential.
Food can be classified into carbohydrates, proteins, and fats and that is it. Carbohydrates are the simplest of the food molecules and have hydrogen to oxygen ratio of 2:1, the same as water. This makes carbohydrates soluble in water and they can easily move around the body in the vast amount of water-based fluids found within. It is this fact that makes carbohydrate the preferred fuel molecule of muscle contraction and brain activity in the human body.
Energy is released when somewhat large molecules (carbohydrates) are broken apart in enzyme controlled biochemical reactions. In humans 25% of this energy is used to re-synthesize ATP molecules used in muscle contractions, while 75% of the energy is lost as heat. A chocolate candy bar with about 200 KCAL of mostly carbohydrate molecules has more potential energy than an apple with 100 KCAL of potential energy. Thus, more ATP molecules can be re-synthesized for running an 800 meter race with energy from a candy bar than an apple. But of course, the chocolate has no added vitamins, minerals, or fiber that speaks nothing of energy potential but is necessary material to maintain life in other ways. There is also the rate by which carbohydrates are broken apart with chocolate being a simple carbohydrate and breaking apart quickly, while an apple is a complex carbohydrate and breaks apart more slowly. The rate of potential energy conversion in the system favors the apple but the total potential energy favors the chocolate.
Proteins are consumed daily and can be used as fuel in certain high-stress situations, but generally these molecules are used as the raw materials for the constant cell repair that occurs in the body. If one compounds daily life with middle distance training, then the need for protein increases because of increased body cell damage. The protein molecule itself consists of amino acids linked together in short or long chains depending on the complexity of the role of the particular protein used in maintaining life. There are 20 different amino acids that are consumed in plant and animal protein and their re-formation into unique and distinctive proteins in the human body is directed by the genome. Thus, all human proteins differ slightly from individual to individual.
Fats are consumed daily and have very high hydrogen to oxygen formula ratio and are not soluble in water. This fact alone relegates most fat molecules to immediate storage unless the daily activity rate is so high that fat calories are essential in supplementing the carbohydrate calories to maintain vitality and life. This is many times the case with middle distance runners in training. Some fat molecules are used by the constantly beating heart everyday so as to stay out of nutrient competition with the other vital organ of the body, the brain. Fat molecules are very large with many chemical bonds holding them together. They contain more potential energy in calories than both carbohydrates and proteins, but the complexity of the molecule necessitates many more steps for energy release in the biochemical reactions. This takes additional bio-reaction time. Thus, fats are of use as an energy source only in low energy demand situations such as those activities at aerobic threshold and below.
The number of KCAL and recommended consuming percentages each day of the three types of food for a middle distance runner are found in Table 1.
The number of KCAL used to complete a middle distance race to exhaustion at race pace is found in Table 2.
Notice in Table 2 that the 800 meters is nearly half as far as the 1500 meters, which significantly makes it a faster race, yet the anaerobic KCAL contribution is the same. The big energy differences in the two events are in the aerobic energy system calorie usage. The effect of this anaerobic phenomenon is not the importance of total calories, but calories consumed per second and will influence training for those events. Thus, we get into the incomplete cleavage of the carbohydrate molecule in glycolysis and the greater the formation of fatigue causing hydrogen ions and lactate accumulation the shorter the race. That is a topic for later discussion.
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