Skip to content

Study after study finds health benefits from exercise of all sorts, but what about those people who are so fit that they run marathons longer than normal marathons of 26.2 miles?

This study looked at those who participate in extreme events include ultramarathons, which tend to be 30 to 50 miles long, but can be more than 100 miles long or even last 24 hours. One study published in 2014 found that "compared with the general population, ultramarathon runners appear healthier and report fewer missed work or school days due to illness or injury...have a higher prevalence of asthma and allergies than the general population" and they may get some "exercise-related injuries such as stress fractures involving the foot."

But this newly published study found that the effects of extreme exercise (because it causes changes in the gut wall and allows bacteria to leak into the bloodstream) can be very serious if you haven't trained properly and over a long period of time.

From Medical Xpress: Extreme exercise linked to blood poisoning

Researchers have discovered that extreme exercise can cause intestinal bacteria to leak into the bloodstream, leading to blood poisoning. Experts at Monash University monitored people participating in a range of extreme endurance events, including 24-hour ultra-marathons and multi-stage ultra-marathons, run on consecutive days.

"Blood samples taken before and after the events, compared with a control group, proved that exercise over a prolonged period of time causes the gut wall to change, allowing the naturally present bacteria, known as endotoxins, in the gut to leak into the bloodstream. This then triggers a systemic inflammatory response from the body's immune cells, similar to a serious infection episode. Significantly the study found that individuals who are fit, healthy and follow a steady training program to build up to extreme endurance events, develop immune mechanisms to counteract this, without any side effects.

However individuals who take part in extreme endurance events, especially in the heat and with little training, put their bodies under enormous strain above the body's protective capacity. With elevated levels of endotoxins in the blood, the immune system's response can be far greater than the body's protective counter-action. In extreme cases, it leads to sepsis induced systemic inflammatory response syndrome, which can be fatal if it is not diagnosed and treated promptly.

The study, led by Dr Ricardo Costa, from the Department of Nutrition and Dietetics, is the first to identify a link between extreme endurance exercise and the stress it may place on gut integrity. "Nearly all of the participants in our study had blood markers identical to patients admitted to hospital with sepsis. That's because the bacterial endotoxins that leach into the blood as a result of extreme exercise, triggers the body's immune cells into action."

Dr Costa said anything over four hours of exercise and repetitive days of endurance exercise is considered extreme...."It's crucial that anyone who signs up to an event, gets a health check first and builds a slow and steady training program, rather than jumping straight into a marathon, for example, with only a month's training," he said.

The research team found that people who were fitter and trained over a longer period of time leading into the ultra-marathon event had higher levels of Interleukin 10 – an anti-inflammatory agent, which allowed them to dampen down the negative health impacting immune response.