Tuesday, April 28, 2009

Running makes me nauseous.

If this blog post sounds familiar it's because I've written about it in a previous post and I'm still looking for a solution. My nausea creeps in at about mile 14 to 16 and then, by mile 18 to 20, it becomes unbearable and impacts my performance. During last Saturday's 20 miler the wave of nausea became so intense I had to stop at mile 18 and wait, hands on knees, for about a minute for the wave to pass. It's the nausea, not the 26.2 miles, that is my biggest race day fear. I've GOT to do something about it!
According to
Dr. Lindsay Weight here are 7 possible causes to running nausea: 1) too little glucose, 2) too much glucose, 3) too little fluid, 4) too much fluid, 5) too little blood supply in the gut, 6) too much movement, 7) sheer effort. The trick is to find the cause, or combinations of causes. Here a thumbnail sketch of the possible causes (with thanks to Dr. Lindsay Weight).
Too Little Glucose:
The most common cause of running nausea is a decrease of glucose in the blood, aka hypoglycemia or low blood-sugar. It usually occurs in runners at the 2 hour mark who have not ingested enough carbohydrates (the body converts glucose -the fuel for muscles- from carbohydrates). Runners can only store enough carbohydrate in their body for the first 2 hours of a marathon, after that, we're running on empty unless we replenish carbohydrates as we run. Symptoms include nausea, light head, poor concentration, and a rapid decline in speed. In running jargon, you've hit the wall.
Too Much Glucose:
Ingesting fluids containing carbohydrate at a rate faster than it can be consumed by the stomach. The stomach is a small organ and can hold the equivalent of one can of pop. If you consume fluids faster that the stomach can cope, the fluid backs up your esophagus into your throat and out the mouth... vomit!
Too Little Fluid:
It's not unusual for marathoners to experience mild dehydration. Runners tend to lose between 700 and 1500 ml of water through sweat every hour. It's very difficult to drink more than 800 ml of water an hour so some water loss is inevitable. Losing 2 to 3% of your body mass through sweating is not a huge deal and shouldn't effect your performance. Losing between 4 and 5% constitutes dehydration and will effect your performance and may cause nausea. Losing over 5% of your body weight through sweat is dangerous and will shut you down mighty fast. The solution? Drink between 150 and 200 ml every 15 minutes. If you lose a 1000 ml of water an hour and only consume 200 ml every 15 minutes you're still left with a 200 ml water deficit per hour, or 800 ml over the course of a 4 hour marathon, but at least the dehydration is in the safe zone and shouldn't impact performance or cause nausea. Remember, 150 to 200ml every 15 minutes, the equivalent of 3 big gulps of water... GULP, GULP, GULP/ 15 minutes.
Too Much Water: This is a very rare condition which has been grossly exaggerated and hyped over the last several years. Too much water dilutes your sodium levels and will cause severe nausea. It's more common in inexperienced walkers.
Too little blood supply in the gut: Even if you're well hydrated the amount of blood going to your stomach is reduced because the blood supply is diverted to the big leg muscles. Over the course of several hours of running the supply of oxygen and nutrients to the stomach is greatly reduced. To make matters worse, the stomach does not take kindly to hours and hours of liquid intake with no solids. The abuse to the stomach can cause nausea; think of it as a punch in the gut.
Too much motion: The up and down motion of the head can cause a form of motion sickness. The solution is to practice running efficiently;
Sheer effort:
Running puts the body under metabolic stress. The higher the intensity or the longer the duration the more stress and the more likely you are to feel nauseous as your system is overwhelmed by the demands placed on it.
Now for the self-diagnosis.... I think my nausea is caused by a combination of three things: 1) too little glucose (hypoglycemia), 2) to a lesser extent, too little water (dehydration), 3) and gels (yuck... just the thought of them makes me wretch!). If I had to choose only one possible cause, I'd be picking hypoglycemia. It just seems to fit my profile. The solution? ... consume more carbohydrates (other than gels) during the race and do a better job of carb loading the week leading up to the race. In addition, be more aware of dehydration creep. Drink three big gulps of liquid every 15 minutes during a race, and finally, leave the bloomin' gels at home. I need to find a replacement for the gels; something that will give me a quick burst of carbs but won't destroy my stomach (power bars? sports drinks?). I have four more long training runs before the MB full marathon so I'll give it a try. Here's hoping for a solution!
Good luck to everyone running the Cops for Cancer race this Sunday. I'll see you at the start line. Let's getter done!
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