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Image: Dara Torres
American swimmer Dara Torres stretches during the team's first practice in Sydney. Physiologists say elite swimmers have bodies that are particularly suited to their sport - but there's more to winning a medal than biomechanics.
By
Special to msnbc.com

So you want to win an Olympic gold medal? Presuming you’ve already been born, it may be too late. But even if you were smart and chose your parents well, it’s still no sure thing that the genetic gifts they gave you will turn into a trip to the medal stand.

Did you ever notice that high jumpers seem to have really long legs? High-hurdlers too. A really long inseam (the distance from the inside of the crotch to the ground) means two things:

1. You can’t shop for a standard pair of pants.

2. The part of your body from the crotch up has less distance to travel to get over those bars or hurdles. You don’t have to propel your heavy torso as high. That’s how those high-hurdlers manage to look like they’re not jumping over those hurdles. They aren’t. Their extra long legs mean they don’t have to. They just stretch their legs and let their inseam do the rest.

That’s an obvious example of how genetic advantage can make the difference between an athlete, and a world-class athlete. Elite competitors are born with external physiology — body size, shape, and mechanics — that give them a leg up (or a hand or an arm or a back) over us mortals. It would be pretty tough to develop a longer inseam through training, short of some really uncomfortable time on the rack.

Basketball players need height. Weightlifters do better if they’re short so they don’t have to clean and jerk the weight as far. The typical elite rower is a few inches past 6 feet. So are swimmers. The height gives them leverage. (Being born with long arms helps, too.) Distance runners are thin — ectomorphic body types, with less weight to carry. Wrestlers, decathletes, weightlifters and other athletes in sports more geared to quick bursts of power than long tests of endurance are born mesomorphs, bigger body types with more gross muscle mass.

Elite athletes also benefit from a genetically based body fat ratio that gives them more muscle, less fat than us couch potatoes. They also enjoy better mechanics. Their bodies work to run swim, jump, tumble … whatever … more efficiently. While good performance mechanics can be trained, elite athletes start out with superior mechanics, and then train to get even better.

Going deeper
But not everyone who’s 6-foot-8 will play basketball. Not everyone under 5-foot-5 will lift weights. And not all 6-foot-8 basketball players or 5-foot-5 cleaner-and-jerkers rise within their sport to world-class level. Those who win gold have still more genetic advantages. They have the right kind of muscles, and a superior ability to restore internal biochemical energy.

Some of our muscles twitch quickly. They generate a lot of power immediately, but for only several seconds. Weightlifters’ legs, which can produce standing vertical leaps of more than 3 feet, are mostly fast twitch. Sprinters are also born with a higher-than-normal percentage of fast-twitch muscles.

If, however, you have to twitch for more than two hours in a marathon, or participate in any sport that emphasizes endurance, you have an edge if you were born with more of the slow-twitch muscles that don’t generate as much power as quickly but continue to produce energy much longer. The legs of Olympic marathoners are as much as 90 percent slow-twitch.

You can train the muscles you have, but you’re pretty much stuck with the fast-twitch/slow-twitch ratio with which you’re born.

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Then there’s the biochemical machinery deep inside those muscles. All of us depend on a molecule known as adenosine triphosphate to produce energy. There is ATP stored in our muscles before the gun goes off. But we don’t store the stuff well, and we burn it in a hurry. If you’re working hard, you use the 5 millimoles of ATP stored in every kilogram of muscle in about five seconds. That’s good for about half of a 100-meter dash.

Three systems
We have three interrelated ways to produce ATP. The first comes from those fast-twitch muscles, that produce a molecule called phosphocreatine that breaks down into ATP. About halfway into the 100-meter sprint, the runners are out of stored ATP and switching over to their internal phosphocreatine system. You will not be able to notice this on TV!

But the phosphocreatine system is only good for another 5 to 10 seconds. After that, the body switches to an anaerobic (“doesn’t use oxygen”) system called glycolosis that converts carbohydrates into ATP. But that produces the byproduct lactic acid. After two minutes or so, the lactic acid has built up so much that your muscles burn, impairing performance.

So the athlete internally switches to system three: aerobic (“uses oxygen”) metabolism, which converts carbohydrates and fat into ATP. Aerobic metabolism doesn’t start until after a couple minutes of hard exercise. When it does, it puts the phosphocreatine and anaerobic glycolosis systems into standby, so we can call on them for quick bursts of energy in the middle of a game of water polo or soccer, or for a sprint at the end of a race.

We can all train to enhance the performance of these systems, but they’re more efficient in elite athletes. From the time he was first measured at age 15, Tour de France-winning cyclist Lance Armstrong had twice the ability to use oxygen during exercise, known as VO2max, as the average person.

But for all their inheritance, elite athletes can’t just pop off the couch and sprint to gold. Cardiovascular systems can be trained to develop higher VO2max. The lactic acid threshold, when too much of the stuff starts to interfere with performance, can be improved. Weekend warriors hit their lactic acid threshold at 60 percent of VO2max. Olympians don’t hit it until they’re at 80 to 85 percent.

Even blood can be taught to work better. Endurance athletes spend years “Living High, and Training Low.” Life at altitude, where there is less oxygen per unit of air, encourages the body to permanently produce more oxygen-carrying red blood cells. But while they’re actually running or swimming in training sessions, athletes at high altitude can’t go as fast or last as long. So the actual training part is done at sea level. (To do this without racking up the frequent-flier miles, U.S. Olympic athletes who live at 9,000 feet in Colorado train wearing breathing apparatus that supplies sea-level amounts of oxygen. Athletes who train at sea level in California sleep in tents that simulate oxygen levels at altitude.)

The mental factor
Finally, there is mental capacity. Athletes maximize their performance using techniques like meditation, muscle relaxation, visualization (seeing yourself doing something before you do it, so you do it more the way you want) and tricks to help with concentration. Former Olympic diver Greg Louganis says he used to tell himself jokes just before diving, to clear his mind of distractions.

Genes don’t seem to help here. You and I can train our brain as well as any gold medalist.

And mental training may be the most important of all. When every elite athlete at the starting line has the same body type, the same muscles, the same biochemistry and the same training, and when the average difference between gold and silver is less than a second or fractions of points on a judge’s score, the way to make sure it’s your national anthem they play may be more in your head than your body.

David Ropeik is a longtime science journalist and currently serves as Director of Risk Communication at the Harvard Center for Risk Analysis.

© 2013 MSNBC Interactive.  Reprints

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