Denaturing Endurance;

Understanding proteins is a great place to start when you want to push the limits of biology. Proteins are responsible for most of the functions of life, and many of the critical processes of metabolism which facilitate endurance exercise are mediated by proteins. Proteins sit like little ice bergs in the seas of cell walls throughout our muscles, and they facilitate sugars entering and exiting the cell. Hemoglobin is another protein critical to endurance exercise, which is present in red blood cells and facilitates the movement of oxygen during exercise. Proteins act as small machines in the body, accomplishing specific tasks, which working together produces the great symphony of metabolism.

Most people think about protein in meats and in the foods we eat. Proteins undergo a specific change when heated, a process known as denaturing. Proteins are long chains of amino acids, with each amino acid having a slight twist or bend. The shape of the protein, as well as its function, depends on the amino acids which make up it’s chain. Because of the interaction between molecules, some amino acids will seek to move towards one another, folding the chain back on itself and forming a three dimensional shape. These attractions are polar, typically between positive and negative areas of different amino acids, but they are not chemical bonds.

When cooked, the molecules in protein have more energy, and the attractions break down. The long chains of amino acids will unfold without their attractions, and can even cross link with other proteins in the area. This unfolding is the process of denaturing, and heat is not the only way it can occur. Acids and alcohols can also cause denaturing. Denatured proteins no longer perform their original functions; cooked meat can no longer sustain metabolism.

In a prior post, we discussed reasons why acidity increases in the body during endurance exercise. In short, aerobic metabolism produces large amounts of carbon dioxide, which when dissolved in the blood becomes a weak acid. In addition, an-aerobic metabolism produces a surplus of hydrogen ions directly, which is by definition acid. Both of these factors tend to denature all the proteins in our body, especially during vigorous exercise.

As discussed above, high temperatures can denature proteins. Proteins tend to be specifically adapted to the temperature of a life forms typical environment, with some animals (like humans) maintaining a warmer environment within their body. The proteins in cold water fish are active at much lower temperatures, and as a result they denature ( and cook) at much lower temperatures. Endurance exercise results in excess heat in the body, which must be lost to the environment a person is exercising in. If the body temperature keeps rising, proteins denature and cease to function properly.

Exercise gets harder with more intensity largely because of the proteins responsible for life breaking down under the intense pressure of temperature and acidity. As discussed in a prior post, the main way to decrease the acidifying presence of Carbon Dioxide in blood is to exhale it away. High body temperatures can be addressed the same way, as well as by sweating, or moving quickly through a cooler environment.

So on hot days, take it easy. You may feel great, but as you push, you are literally fighting physics to perform. As you train, much of the adaptation that permits higher power output for longer is temperature acclimation. Keep this in mind during trainer season; a few degrees higher ambient temperature in your pain cave dramatically affects perceived exertion at the same power.