Sunday, July 5, 2015

Blood Poisoning In Extreme Endurance Events

Picture by orangefan_2011 from Flickr
If you haven't trained hard enough for your upcoming marathon or ultra marathon race, beware for there may be more adverse effects than you think.

Extended exercises beyond four hours can put your body at risk if you are not sufficiently prepared. Stomach bacteria may seep into your bloodstream and cause poisoning.

Two different studies looked at runners taking part in two different ultra distance races in Scotland (between 78-130 miles) and Spain (5-day 143 miles stage race).

Before and after the races, blood samples were taken from the runners and a control group not racing.

Blood markers in most of the runners after the races showed traces of blood poisoning. This was similar to what you see if you were admitted to the hospital for food poisoning. Almost all the runners had stomach issues during the race as well. None were hospitalized though.

Some runners even had blood markers resembling those who have sepsis - a potentially life threatening illness where chemicals released into the bloodstream to fight infection actually generate heavy inflammation.

This happens when blood moves away from the stomach area to the working muscles when we exercise. This causes the stomach wall to spread apart and leave open gaps. Endotoxins (naturally occurring bacteria in the stomach) fit through these gaps and leach into the blood. This activates an inflammatory response in the body.

Usually the body can easily clean up this sort of bacteria leaching. Only under heavy duress the body can be overwhelmed. This can occur in extreme exercise conditions, heat stress, illness and infection.

When the weather is hot, blood flow away from the stomach to the working muscles will be more extreme, so strategies to keep the body cool during training and racing is critical.

The researchers added that repeated bouts of inflammation like this can cause long term fatigue, stomach problems and immune disturbances.

What was interesting was that in both studies, runners who trained sufficiently had higher levels of Interleukin-10, a small anti inflammatory protein that helps offsets negative health effects.

Now you know, make sure you train enough for your race.


Gill SK, Hankey J, Wright A et al (2015). The Impact Of A 24-h Ultra-marathon On Circulatory Endotoxin And Cytokine Profile. Int J Sports Med. 36(8): 688-695. DOI: 10.1055/s-0034-1398535.

Gill SK, Texeira A, Rama L et al (2015). Circulatory Endotoxin Concentration And Cytokine Profile In Response to Exertional-heat Stress During A Multi-stage Untra-marathon Competition. Exerc Immunol Rev. 21:114-128.

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