You know about the thrill of victory and the agony of defeat, but how about the agony of running a marathon?</p><p>Running 26.2 miles is quite an accomplishment. But &#8220;bonking&#8221; or &#8220;hitting the wall&#8221; may be the most excruciating feeling &#8212; physically, at least &#8212; a runner can experience.</p><p>That&#8217;s what happens when an athlete&#8217;s body runs out of energy. It&#8217;s almost certain to occur to someone running in Saturday&#8217;s Kansas City Marathon.</p><p>Mark Conover described the feeling that overcame him at mile 22 in an article he wrote at ontherunevents.com.</p><p>&#8220;I walked nearly a mile, then started jogging it in, looking ahead on the long, straight, tulle-fog infested road for any sign of a finish line,&#8221; Conover wrote. &#8220;My legs were reduced to moving bones with muscles so depleted of glycogen and so laden with lactic acid that it&#8217;s a wonder I was able to finish at all. My mind was numb, kind of like what happens if you have to listen to a jackhammer all day long. Actually, my whole body felt like a jackhammer &#8212; a shattered one.&#8221;</p><p>John Ivy, chairman of the department of kinesiology and health education at the University of Texas, explained why a runner bonks.</p><p>&#8220;It&#8217;s believed that what happens is the body becomes depleted of carbohydrates, particularly muscle glycogen,&#8221; Ivy said in a phone interview. &#8220;Without the available carbohydrate in the muscle itself, then the muscle has the inability to generate energy fast enough to continue that race pace, so people become highly fatigued.&#8221;</p><p>Your muscles need energy to contract, and they are fueled mainly by the glycogen stores in muscle cells.</p><p>When you eat carbohydrate, it is converted into glucose and other simple sugars in the gut. The glucose passes into the circulatory system and is transported into the muscle and converted in glycogen, where a small amount is stored in the liver. Most is stored in muscles.</p><p>Still, the muscles can hold only a certain amount of glucose and when it&#8217;s gone, your body lets you know.</p><p>&#8220;When depletion of muscle glycogen stores occurs, this results in fatigue because blood glucose cannot be taken up by the muscle fast enough to supply all the carbohydrate needed to fuel the muscles,&#8221; said Ivy, who co-authored the book <em>The Performance Zone: Your Nutrition Action Plan for Greater Endurance and Sports Performance</em>.</p><p>It&#8217;s important for a runner to build up glycogen stores. This is why high school cross country teams hold spaghetti dinners the night before a race.</p><p>&#8220;That&#8217;s part of the glycogen storing process,&#8221; Ivy said. &#8220;You want to take in large amounts of carbohydrate the night before to help you store glycogen.&#8221;</p><p>Gorging on carbohydrate is called glycogen loading or (and this sounds cooler) glycogen supercompensation.</p><p>Oh, and by the way, the runners should go ahead and have meatballs.</p><p>&#8220;Protein along with carbohydrate does seem to help with the glycogen storing process,&#8221; Ivy said.</p><p>During a marathon, an athlete will burn at least 2,500 calories. So it&#8217;s no surprise that runners often hit the wall. There are things a runner can do during a race to prevent &#8212; or at least delay &#8212; bonking.</p><p>&#8220;It is also important to consume carbohydrate during exercise as this will ensure that blood glucose remains elevated late in exercise when liver glycogen stores are depleted,&#8221; Ivy said. &#8220;Maintaining blood glucose levels will help reduce the reliance on muscle glycogen and help prevent muscle glycogen from being depleted.</p><p>&#8220;Drinking sports drinks during race can help you sustain that exercise intensity so that you&#8217;re running at least a little while after the muscle glycogen stores are depleted. It will give you another 25, 30 minutes of running if done properly.&#8221;</p><p>And help avoid an agonizing race day, too.