Dr. Jason R. Karp December 28, 2011 TWEET COMMENTS 3

Marathon Training Guide - Page 2

Marathon Training

In a marathon, the main difference from shorter races is that you run out of carbohydrate, which is your muscles' preferred fuel. You have enough stored carbohydrate (glycogen) in your muscles to last slightly more than two hours of sustained running at a moderate intensity. So, unless you plan on running the marathon as fast as Haile Gebrselassie, you're going to run out of fuel. Glycogen depletion and the accompanying low blood sugar (hypoglycemia) coincide with hitting the infamous wall.

Other issues not encountered in shorter races that affect marathon performance include dehydration, muscle-fiber damage, increased body temperature (hyperthermia) and psychological fatigue. When you sweat a lot, you become dehydrated, which causes a decrease in the plasma volume of the blood, decreasing the heart's stroke volume and cardiac output. Oxygen flow to your muscles is then compromised, and the pace slows.

The relentless pounding causes muscle-fiber damage, which decreases muscle-force production. Since your muscles produce heat when they contract, running for long periods of time increases body temperature and the resulting hyperthermia decreases blood flow to the active muscles since more blood is directed to the skin to increase convective cooling. Finally, running for so long can cause psychological fatigue, the latter of which is due to changes in the levels of brain neurotransmitters.

High Mileage

While high mileage is important for the 10K, it is especially important for the marathon to maximize your aerobic capacity. This may even require running twice per day to spread out the stress and maximize recovery. In addition, research has shown that runners who perform high volumes of endurance training tend to be more economical, which has led to the suggestion among scientists that running high mileage (greater than 70 miles per week) improves running economy.

Running's repetitive movements result in improved biomechanics and muscle-fiber recruitment. Additionally, economy may be improved by the weight loss that usually accompanies high mileage (a lighter body needs less oxygen than a heavier body); the growth of slow-twitch skeletal muscle fibers; and the greater ability of tendons to store and use elastic energy with each step.

Long Runs

The main difference between 10K training and marathon training is the inclusion of long runs in your program, with the amount of time spent on your feet being more important than the number of miles you cover. Repeatedly running for more than two hours presents a threat to the muscles' survival by depleting their store of glycogen. However, the human body responds rather elegantly to situations that threaten or deplete its fuel supply: It synthesizes and stores more than what was previously present, thus increasing endurance for future efforts. Empty a full glass, and you get a refilled larger glass in its place. Much like college fraternity parties. The more glycogen you have packed into your muscles, the greater your ability to hold your marathon pace to the finish.

If you're training for a trail marathon, do most of your long runs on trails so you get used to the uneven terrain, and run in trail-running shoes. While your long run should not comprise more than about 30 percent of your weekly mileage, this rule can be broken if you are only able to run a few times per week. Run at a comfortable, conversational pace (about two minutes per mile slower than 5K race pace, or about 70 to 75 percent of maximum heart rate). Lengthen your long run by one mile each week for three or four weeks before backing off for a recovery week.


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