Friday, April 18, 2014

Endurance Limits -- Glycogen and Electrolytes

In 2005 I had just gotten into road biking. Two years later I would be doing several centuries and double centuries including the Deperado Dual and Lotoja, but in June 2005 I was a know-nothing newbie that was quickly increasing mileage from ride to ride but not wisdom. I was completely unprepared for what would happen one day in June as I attempted an 86 mile ride from Cedar City to St. George, Utah. I had really never experienced what it was like to run out of glycogen stores and to have a severe electrolyte imbalance.

Early that morning I skipped breakfast so that I could save time and arrive in sunny, St. George before the day got too hot. I packed two water bottles and planed on refilling them and buying a snack at a gas station that was about 30 miles away. I got to the gas station before it was open and had to settle for hose water from a nearby house. I hoped that the water coming out of the hose was potable. You never know in farming communities and rural areas. Sometimes the water comes from a ditch or worst, but I had no choice. I had worked up a good, hard sweat riding up, over a mountain pass with two more passes in front of me. It did not occur to me at the time that sweat is not just water, it is water, sodium, potassium and several other minerals that bodies need to function.

My friend Chad and I rode together to the beginning of the next hill. His stomach was upset due to his breakfast. For a while, I was glad I had not eaten. I was feeling good, so I took off, leaving Chad to work on the hill alone. By the time I got to the top I could not see Chad anywhere. I waited at the top for about five minutes then left to go down the steep road to the bottom of the last climb, Veyo Hill. By the time I got to the bottom of Veyo, I was feeling weak and light headed but didn't think much of it. At the top of Veyo, I hit a wall. I could not pedal even one more time. I pulled over to the side of the road, awkwardly fell off my bike onto the gravel and within minutes was seeing purple dragons coming out of the bushes toward me.

Veyo hill is a painful part of the St George Marathon. 

I was hallucinating, cold, disoriented and nauseous. When Chad came by ten minutes later, his gastric difficulty had passed and he was feeling great. I told him I would need a ride to even move in any direction. Since my wife was meeting me in St. George to drive us home, I had her drive to my location. I think Chad continued down the hill to finish the ride. It took ten minutes to stuff my bike into the back of my 4Runner, a task which should have taken two. I was light headed every time I stood up for the next 36 hours, and I wanted to quit riding forever.


Carbohydrates are converted to glycogen stores then to glucose before being used by the rest of the body. The two most common storage reservoirs are muscles for muscle use and the liver for use in the rest of the body. Complete glycogen depletion from extended endurance exercise is called "hitting the wall." There are four ways that hit can be forestalled.

  1. An athlete can consume carbohydrate calories before the endurance event to "top off" glycogen stores and during the event to replenish the depleted stores. The latter is difficult because body processes are limited on how fast they can convert carbs to glycogen to glucose. 
  2. An athlete can train her body to burn a higher ratio of fat to glycogen.
  3. The body can be trained to increase intramuscular stores by going through processes of depleting and carb loading.
  4. Heart, lungs and muscles can become more efficient through training thereby requiring less glycogen to cover the same distance.
In an effort to quicken the carb digestion process, some formula companies, like Twin Labs, have developed nutritional drink additives with multiple sugar sources that are supposed to allow the body to process a higher amount of total carbs and thus replenish glycogen reserves sooner. 

The hallucinations I experienced were due to complete glycogen depletion in my liver and muscles. My body was then looking to my brain for additional glycogen. It is a scary thing that I don't want to experience again.


Glycogen strategy is essential to any endurance event. I calculated that the day I biked Lotoja, a 206 mile, single day event, I burned around 14,000 calories. Of the 14,000, I believe my glycogen stores were the equivalent of 4000 calories. This left a 10,000 calorie deficit to try to intake throughout the day. I knocked out 2500 calories the morning before I got on my bike. From then on it was a race to pound calories all day. 

Lighter people have a huge glycogen advantage in endurance racing. That is why the average tour rider is scalpel skinny. They don't even do pushups for fear of any gain in grams. If they have to push more weight up a hill, they will burn through glycogen faster.

Rasmussen was winning the tour before testing positive for drugs.

Frank Schlesk, useless in a street fight, but he sure can ride.

As part of the strategy for endurance events, it is wise to train your digestive tract to fully function during athletic exertion. It is easier to do during a bike event than a run event. When my marathon running wife went with me on her first 100 mile bike ride, she was shocked at how much I and everyone else ate at the lunch stop. I pounded a large hoagie sandwich, two bags of chips and two large cups of full sugar coke. The most she had ever consumed during a marathon was a few gels, an occasional orange slice and Gatorade. A long distance runner should never say, "hate to eat and run." The opposite is a matter of event survival. 

I make my own gel concoction to be consumed during events that last up to eight hours. It has the advantages knowing every ingredient and it is a lot cheaper than factory produced gel packs. If you know me at all, you know I dig the second part. Here is the recipe:

  • 1/2 C Brown Rice Syrup
  • 1/2 C Honey
  • 1/2 Banana pureed
  • 1/2 tsp Salt 
  • 1 TBS Molasses
  • 1 TBS Hydrated Chia seeds
  • 6 Dates pureed
Brown rice syrup contains both fast and slow burning carbs. Honey is about in the middle. The banana contains potassium and improves the flavor of about everything. Salt, sodium, the most important replenish requirement. Molasses contains glucose, fructose, raffinose and other polysaccharides. It also contains potassium, sodium, calcium and magnesium. Pretty cool, right? The the hydrated chia seeds are fluid sponges that ease water absorption and the dates are yummy superfood. 

When I feel lazy and rich, I buy and consume factory-made gels. My favorites are anything by Hammer Nutrition and Chocolate Accel Gel. It tastes like chocolate ice cream, no kidding. It also contains a shot of caffeine which is the topic of another post. 


Electrolye imbalances have several unpleasant results as indicated in the table below.

I like the article, Electrolytes: Understanding Replacement Options, by Shawn Dolan. The table above comes from his article.

Electrolyte replenishment for long endurance events is a serious matter. If you are the kind of person that leaves a salty residue on clothing after an hour of exertion, you need to be more serious. I am a sweater. I completely saturate baseball hats, shirts, and any hydration pack that I might be wearing when I go long. During super long events of more than 6 hours, once my sweat dries, my shirt can practically stand up by itself. My preferred replenishment method is spiked water and salt tables. There are many effervescent hydration tablets that do a great job. I like these as much as any others. You can find them cheap sometimes at

It will take time to learn how much electrolyte stuff to consume. I suppose there is some scientific way to figure it out, perhaps by taking blood and urine samples every few miles, but this is unrealistic for most of us. Go run or ride long, keep track of the temperature and what you are wearing and test. 

Please let me know how you beat heat, sweat and glycogen depletion by leaving a comment below.

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