Choline - is this the solution to the marathoner's "wall"?
Brian Mackenzie considers a possible reason for why marathon runners experience the 'wall'
"Around 20 miles I just hit a wall, my legs went, and I struggled the last 6 miles". How many times have you heard that from a marathon runner or experienced it yourself? Often the smart response is "well perhaps you should look where you are running" but just what it is that goes on inside the athlete's body that results in this experience?
What makes us move?
The movement of a limb is achieved by exciting a muscle so that it contracts. Muscles do not contract of their accord; they rely on messages from the brain via nerves. A signal is transmitted from the brain to the end of the nerve attached to the muscle which it wishes to contract. There is a small space between the end of the nerve and the muscle and it is across this neuromuscular space that the nerve pushes small quantities of a chemical called acetylcholine. When sufficient acetylcholine attaches to the outer surface of the muscle cell, the muscle cell becomes excited and contracts. Should you run out of acetylcholine then the muscles will not be able to contract, even if they are stocked with energy (ATP). Physiologists reckon that acetylcholine is broken down inside the neuromuscular junctions during prolonged exercise. Nerve cells then "grab" the choline floating by in the blood, using it to make new acetylcholine and as a result, your blood choline levels start decreasing. Naturally, if your choline levels fall too far, acetylcholine production can come to a relative standstill, and your nerve cells will refuse to stimulate your muscles.
What is the function of Choline?
Choline is a vitamin-like compound that is an essential part of the human diet as it is used by the body to produce acetylcholine. Without choline, acetylcholine cannot be produced, and the body cannot function normally. Choline is also an extremely important structural element of cells, especially cell membranes, and is essential for the process of breaking down fat for energy.
Choline and the 'Wall'
When you run a race like the 5km, 10km or half-marathon the choline concentrations remain sufficient. Your choline levels drop dramatically only when you run a marathon or exercise continuously for two hours or more. Some exercise scientists believe that this drop-in choline is behind the devastating fatigue which strikes near the end of a marathon - referred to, by many marathon runners, as the 'Wall'. Some scientists reason that choline supplements if taken at the right time and in the right amount might help the nervous system continue to stimulate muscle cells and keep you striving toward the marathon finish line at your desired pace.
Where does choline come from?
Choline is available in foods such as liver, cauliflower, soybeans, spinach, lettuce, nuts, and eggs. The bottom line is that even a choline-rich natural diet would not prevent the drop-in blood choline levels which happen after 20 miles or so of marathon running.
For a marathon, how much and when?
The right amount is about 2.5 grams, swallowed about an hour before your marathon begins. This additional dosage of choline in your blood may begin to fall three hours after you have taken it (e.g. two hours into your marathon), so it makes sense to take another 2.5 grams at the 10 to 13-mile point of your race.
Are there any side effects?
Physiologists say although Choline is safe to take, a potential problem is an occasional bout of diarrhoea or some pretty foul flatulence.
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About the Author
Brian Mackenzie is a British Athletics level 4 performance coach and a coach tutor/assessor. He has been coaching sprint, middle distance and combined event athletes for the past 30+ years and has 45+ years of experience as an endurance athlete.