Second Wind

 

You have heard about athletes getting their second wind? It is not that they feel better, that they are warmed up and ready to run more easily. It is not psychological (at least, not all psychological). No. There is an actual physiological truth to a second wind.

It all has to do with respiration. When I say respiration, I am not talking about breathing. Respiration is a biochemical process that happens at the cellular level. It is how the cell gets energy. There are lots of chemical processes that are constantly going on in each cell, and those processes require energy. Without a constant feed of energy, the cell will die. The more demands there are on a cell, the more energy it needs. For example, every one of your muscle cells need more energy when you are running.  In fact, you won’t be able to run if the cells don’t have sufficient energy for it.

The energy currency of the cell is a molecule called ATP. You may have heard that sugar is how our bodies get energy, which is true in a way, but the cells cannot get energy directly out of sugar. It’s like an automobile. We know that gasoline is made from crude oil, but if you were to put crude oil in your gas tank, it wouldn’t work very well. Crude oil is refined down to various products, one of which is gasoline. ATP is like gasoline. The cellular process of respiration refines glucose down into ATP. There are two types of respiration: aerobic and anaerobic. Aerobic respiration requires oxygen. When you breath, you are pulling air into your lungs. Oxygen is extracted from that air and bound to blood cells which can carry that oxygen around to the rest of the body. In aerobic respiration, one glucose molecule can produce 38 ATP molecules. 38 packets of energy. If you start to run, your muscle cells need more energy to do the work, which means your lungs have to work harder to get more oxygen into the system. More oxygen means more ATPs can be produced which means more energy is available to the cell which means they can work harder. If you are running really hard, at some point the energy requirements are going to start to exceed the amount that can be produced through aerobic respiration no matter how hard you breathe. Cells that are using more energy than they have available, start to faulter. The muscles start to hurt and start slowing down, which means the runner starts slowing down.

But wait! There is another form of respiration called anaerobic respiration (anaerobic means without oxygen). In plants it is called fermentation. Once you have spent all the available energy and things start slowing down, anaerobic respiration kicks in to supplement aerobic respiration. Anaerobic respiration is less efficient that aerobic respiration. You only get two ATPs for each molecule of glucose. That is significantly less, but it adds to the total already being generated and can give the cells and the runner a little boost. This boost is what is referred to as the “Second Wind.” But there is a downside. While the byproducts of aerobic respiration is carbon dioxide and water (which are expelled with each exhale), the byproduct of anaerobic respiration is lactic acid. It used to be thought that lactic acid damaged muscle tissue, but that belief is no longer held. However, It is possible that the breakdown products of lactic acid can contribute to muscle pain.

No runner ever achieved Olympic glory without getting to the second wind stage in their workouts, even though they may not have realized it. The bonus energy is small compared to aerobic respiration, so it is possible for a runner to be in the anaerobic zone without ever feeling the bonus second wind (though they will feel the pain). As a former track athlete, I have felt that second wind a time or two, but most times, I did not notice it.

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