Ready... Or Not?
If you stand near the finish at Sunday's Marine Corps Marathon, you will see many examples of the body's remarkable ability to adapt to endurance training. Hang around a while and you'll also see what happens when certain bodies
didn't train as hard as they should have. A body won't be ready to run 26.2 miles without some inner adaptations. Here are a few of them:
- A person who is running will feel as if it is about 20 degrees warmer than a person standing still in the same weather. That's why 50 degrees is considered the ideal marathon temperature.
- Ready: Tine body adapts to repeated calls for more oxygen by building more capillaries over time to handle the increased loads, much as a town adds roads to handle more traffic.
- Or not: Untrained sweat glands don't work quickly and don't conserve electrolytes. The body is more likely to fatigue, dehydrate and overheat.
- Capillaries, the tiniest blood vessels, bring vital oxygen and fuel directly to the muscle fibers and also carry out byproducts.
- Ready: The body adapts to repeated calls for more oxygen by building more capillaries over time to handle the increased loads, much as a town adds roads to handle more traffic.
- Or not: An uncharacteristic burst of aerobic effort overwhelms the network. Capillaries become congested and can't deliver fuel or remove byproducts efficiently.
- With each of the 50.000 or so steps a runner takes in a marathon, he hits the ground with the force of three times his body weight. The body's repair system naturally shores up bone cells that are pounded by the impact.
- Ready: Progressively longer bouts of stress, interspersed with rest, make weight-bearing bones harder, stronger and denser.
- Or not: An enormous load all at once can damage bones past their ability to immediately compensate and can cause injuries such as stress fractures.
Fast (and slow) facts
- 11.008 of the more than 31.000 entrants in this year's Marine Corps Marathon have never completed a marathon.
- The average 2009 finishing time in U.S. marathons was 4 hours 25 minutes 47 seconds. (Men: 4:14:22; women: 4:41:50)
- The New York City Marathon was the world's largest last year, with 43.250 finishers. (Marine Corps was eighth with 21.405 finishers)
- A 150-pound runner will burn roughly 2.600 calories during a marathon.
- Nearly 468.000 runners crossed the finish line at 397 US marathons last year.
- The brain does not want the body to run into harm, so it will reduce its electrical impulses to the muscles - in other words, it will stop telling them to move - sometimes long before the body is close to danger.
- Ready: Through hard training, the brain learns it's okay to let go a little and let the body dip into its reserves. The whole body becomes better at managing effort (pacing) so that the brain is never overwhelmed with alarm signals. On a
conscious level, we're all more comfortable and confident doing something we have done before.
- Or not: The untrained brain has little or no experience with an effort of this magnitude. If the runner pushes too hard, the brain receives a cacophony of threatening signals - Temperature is rising! Fuel is disappearing! My engines
can't take much more of this, Captain! - and the ever-cautious brain will pull the plug.
- Bouts of strenuous exercise over time makes the heart larger, stronger and more efficient at speeding oxygen-rich blood and fuel to the muscles.
- Ready: An adult heart at rest needs to pump about five liters of blood per minute, and it does this in about 72 beats. A well-trained athlete's heart, however, can pump the same amount with far fewer beats. When it really revs up, it
can pump 40 liters of blood per minute.
- Or not: An untrained heart that is suddenly jolted into action has to work hard to keep up with demand. In a Canadian study released this week, hearts of some less-fit runners sustained measurable damage during a marathon and took
up to three months to heal.
- Muscle fibers are like microscopic rubber bands: They stretch and stretch, and eventually the weakest break. Specialized cells then prune the torn fibers and replace them with bigger, stronger ones.
- Ready: Trained muscles have already weeded out weak fibers and are able to produce more force with less fatigue.
- Or not: Undertrained muscles are full of untested fibers. Many tear under the strain, causing the muscles to tire prematurely and to be extremely sore for days.
- Muscles use two fuels: glycogen, which comes from carbohydrates and is stored in the muscles and liver; and fat, which is far more abundant. Glycogen burns quickly and easily, like rocket fuel, letting you run fast while limited
supplies last. Fat can carry you for many hours - slowly. Marathoners need to make the best use of both.
- Ready: If a body were a car, distance training would increase both its horsepower and the size of its fuel tank. Trained muscles contain more mitochondria, which are the factories that turn fuel and oxygen into the energy muscles
use. Long training runs deplete the body of glycogen, revving up enzymes in the mitochondria that burn fat, so that next time, the glycogen supply lasts longer. In addition, a trained body stores more glycogen in the first place.
- Or not: The body suddenly demands energy and gobbles the fuel that's most accessible and easiest to burn: glycogen. Within two hours, muscle and liver stores are nearly gone. Carb-rich gels and drinks may postpone the inevitable,
but soon the runner "hits the wall" and slows to a shuffle.
BONNIE BERKOWITZ AND ALBERTO CUADRA/THE WASHINGTON POST | SOURCES: Exercise physiologist Ross Tucker; Runner's World's "The Runner's Body", by Ross Tucker and Jonathan Dugas with Matt Fitzgerald;
"Transient Myocardial Injury, Microvascular Dysfunction and Decreased Segmental Function in Less Fit Recreational Athletes" by V. Gaudreault, et al.; MarathonGuide.com; RunningUSA.org; Marine Corps Marathon.