Exercise Physiology 101

Nerd alert. This post is going to be a little scientific, so lets get physical (as in lets discuss physiology). And if it’s too much, just skip ahead to the “Take Home Messages” at the end to get a very fast run down of everything that I will now take 10 paragraphs to explain…

Nutrition and physical activity go hand in hand because activity demands carbohydrates and fat as fuel, protein to build and maintain muscle, and vitamins and minerals to support energy metabolism and tissue building. And of course you need water to help distribute fuels and hydrate.

Two terms I would like to share with you today are ATP and CP.

ATP: Stands for adenosine triphosphate. This is a form of energy that is available for immediate use in the body. All energy- yielding nutrients (carbohydrates, protein, and fat) can enter metabolic pathways to make ATP.  Small amounts of ATP are stored in tissues at all times, even during rest, and in the muscles ATP provides the chemical driving force for contraction (think about how often you are moving your muscles, like always). When an ATP molecule is split, it’s energy is released and the muscle cells channel the energy into mechanical movement or as heat.

CP: Stands for creatine phosphate. CP is made from creatine, a compound found in muscles. This compound can split anaerobically (without oxygen) to release a phosphate and replenish ATP supplies. What this means to you is, this is the short term fuel for our bodies. When we participate in high intense boughts of exercise (like a sprint 100-meter dash) our bodies can use CP to produce energy quick and without oxygen. This energy source however usually last for only a matter of seconds. It also acts as a replenishment for ATP. When your muscles are resting, ATP feeds energy back to CP by giving up one of its phosphate groups to creatine. Therefore, CP is produced during rest by reversing the process that occurs during muscular activity.

Are you sufficiently confused already?

Well think of this. ATP and CP are stored in small amounts in your body. If you tried exercising with zero fuel (aka food, energy, calories, however you want to say it) how long do you think your activity would last? Not so long. So this is why it is important to have adequate food and energy stores to perform well. Carbohydrates, fats, and proteins store in our bodies to be utilized during activity.

After you consume carbohydrates, your body stores whatever is not needed right away in a storage form called glycogen. Glycogen is saved or stored in your liver. Your body can then go shopping for energy when you need it. Like when you haven’t eaten for 4 or 5 hours and your body starts needing back up energy, or to sustain ATP production during exercise.

How much carbohydrate a person eats influences how much glycogen is stored. When a person is exercising, glycogen will last depending not only on diet, but also on the intensity of the activity. For example, moderate activities like jogging when breathing is steady and easy, use glycogen stores slowly. But during intense activities, like sprints or races where it may be difficult to “catch your breath, ” glycogen is used up real quick. Usually, a person’s glycogen stores are used as fuel for the first 20 minutes of exercise. After 20 minutes of exercise a person who continues exercising moderately begins to use less and less glycogen and more an more fat for fuel. Have you heard that you don’t start burning fat until 20 minutes into a work out before? Well its absolutely true.

During the first few minutes of utilizing fat as a fuel, your body is calling on free fatty acids circulating in the blood stream. After blood levels fall, the body calls on a hormone epinephrine to signal fat cells to break down and release their stores of triglycerides. Therefore, sustained, moderate activity uses body fat stores as it’s major fuel. So get a good 45 minute to hour work out if you really want to see that fat melt off ya! But in this case, the intensity of the work out also affects the utilization of fat stores, As the intensity of activity increases, fat makes less and less of a contribution to the fuel mixture. A lot of oxygen is needed to break down fat for energy , and if a person is breathing easily during activity, the muscles are getting all the oxygen they need and are able to use more fat. So moral of story, if you want to burn fat, look for activities that require a steady but longer duration. Moderate long distance runs, swimming, and bike rides are good activities. Or any sort of aerobic class or activity that keeps the heart rate pretty moderate.

The longer you train or stick to an activity, the body gets better at permitting the body to draw more heavily on fat for fuel. Also the heart and lungs become stronger and better able to deliver oxygen to muscles at high activity intensities. This explains why sometimes it may take a few months of training and consistent exercising to get your body to start burning fat and to see results. So don’t give up!

Protein is actually not a a major fuel for physical activity. Nonetheless, physically active people need an ample amount of protein in their diets to build muscle and lean tissue. Eating carbohydrates before exercise is needed to prepare your glycogen stores for utilization, but carbohydrate intake coupled with protein after an activity is important to replenish those lost glycogen stores and promote muscles synthesis. Don’t worry, I will dedicate a whole blog to amounts and eating guidelines, but for now it is important to say that it is important to have protein to rebuild muscles.

Only ten percent of the total fuel used during exercise comes from proteins and amino acids, but during activity, muscles turnover amino acids stores much quicker, and protein must be provided at the end of the work out to make sure you have bigger muscles in the end and not wasting ones. Longer work outs, after all the glycogen and fat stores are used, then rely on protein stores. So endurance athletes require the most protein during a work out than any other athlete, even body builders who actually use less protein during an activity. Weird huh?

Quick take home messages:

  • ATP and CP are energy sources in your body. ATP is made aerobically and requires carbohydrates, fat, and protein to produce ample amounts. CP is used to replensih ATP and for short intense energy and does not require oxygen to be utilized.
  • Carbohydrates are your body’s first means to get energy. When you eat carbohydrates, excess amounts are stored as glycogen in your liver to be used for later use and during work outs.
  • Glycogen stores are usually used for the first 20 minutes of a work out, even quicker if the activity is intense.
  • Fat stores are used after 20 minutes of a work out. Longer moderate activities require the use of fat fuels. The longer you train and the greater your lung’s abilities to provide sufficient oxygen, your body will use fat as a major fuel during activity.
  • Protein is needed for recovery and muscles replenishment and building. Protein is used as fuel source only in long duration activities (sport’s games or long runs).
  • And finally,

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2 thoughts on “Exercise Physiology 101

  1. Pingback: What Can Carbs do for You? | cabbagepatchcait

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