A couple of nights back, I watched a fascinating special about the science of running marathons. Months before the Boston Marathon, Novaput together a marathon team representing a regular, old, cross-segment of society. Of the 13 members of the team, most are over-weight or have a very high BMI. Nova wanted to see if these regular people could achieve most folks scoff off as impossible: running the Boston Marathon. The 13 members of Team Nova, were followed through nine months of training. (For more about the show: http://www.pbs.org/wgbh/nova/marathon/)
Different athletes have different physiques that allow them to excel at their sports. Football players have large upper bodies with bulky muscles for short bursts of power (fast-twitch). Futbol players have sinewy muscles, that may look scrawny, but are actually much more efficient at carrying oxygen to the muscles over long distances (slow-twitch). So what did the “normal” people need to do in order to become marathoners?
VO2max is the most important aspect to a person’s strength endurance sports. It is also a good gauge of overall cardiovascular health. VO2max is the “volume of oxygen a person can consume in one minute as they exercise at maximum exertion.” In endurance sports, you rely on oxygen to convert the polysaccharides (sugars) into energy for your muscles, so your efficiency at dispersing oxygen through your body is critical during long distance runs, such as, let’s say, the Boston Marathon. Elite endurance athletes can consume huge amounts of oxygen when they compete. Some of their VO2max scores are twice as high as most of us mortals. For example: Lance Armstrong once measured in at 83.8 ml/kg/min, while the average man at his age would only get between 40 and 50. We are all born with a genetic range for a certain VO2max, and this is why most of us will never become champion runners, but despite the importance of genetics, we can improve our VO2 through exercise.
Given that VO2max is a measure of oxygen consumption, most people believe that lung capacity, “the volume of air a person can inhale in a single breath,” is an important factor. Not so, as lung size is not a limiting factor and most people inhale more than they can ever use anyway. From the lungs, oxygen diffuses into the bloodstream. Then, it attaches to the iron-based protein hemoglobin on red blood cells, which carry the oxygen to the multitude of cells requiring energy. Naturally, smoking and diseases like anemia will decrease your oxygen carrying ability. Runners also create high numbers of red blood cells for transporting oxygen. Training at high altitudes where the air is thin can create more red blood cells. Exercise creates new capillaries, tiny blood vessels that supply oxygen to the muscles. Exercise can also make the blood vessels everywhere less stiff, improving blood flow and reduces clogs in veins and arteries.
The greatest input to VO2max scores is cardiac output, “the amount of oxygen-rich blood your heart can send throughout your body in a single minute.” Through exercise are hearts actually increase in size, bettering our cardiac output, which is “the product of heart rate (the number of beats per minute) times stroke volume (how much blood the heart ejects with each contraction).”
A person’s ability to grow slow- or fast-twitch muscle is mainly genetic, but by training in ways to strengthen a specific type of muscle we can gain each one in turn. The key to efficient energy production are mitochondria, tiny cell organelles that act as power plants. Mitochondria combine oxygen with glucose to make ATP (adenosine triphosphate), which powers cellular work. In muscle cells, ATP is essential for muscle contraction and therefore motion. Slow-twitch fibers hold more mitochondria than fast-twitch. Exercise, again, increases the number of mitochondria and makes mitochondria larger and more metabolically active. In order to contract and relax, the muscle protein, actin, will use ATP to “shuffle” or “walk” up and down the other protein, myosin. “Better,” mitochondria also lower muscle fatigue. Sore muscles during exercise are linked to a buildup of lactic acid, which is a byproduct of anaerobic respiration, where glucose is converted to 2 ATP molecules without oxygen, this is much less efficient, and produces the burning lactic acid. Aerobic respiration, by comparison, produces 36 ATP molecules with oxygen. Glucose is converted to pyruvate through glycolysis in the cell. The pyruvate is then moved into the mitochondria where it is stripped of its H+ ions in the Krebs Cycle. These will pass through the mitochondria membrane creating a proton gradient, a difference in electrical charge. When the ions pass back through the membrane they go agains the gradient, producing energy to combine a phosphate to ADP (phosphorylation), in order to produce ATP, the energy molecule. (http://biology.clc.uc.edu/courses/bio104/cellresp.htm)
A Diagram of Cellular Respiration
There is a runner in all of us and it just takes some hard work to achieve that.
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