Australian researchers have discovered that extreme exercise can cause intestinal bacteria to leak into the bloodstream, leading to blood poisoning.
Experts at Melbourne-based 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 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 programme to build up to extreme endurance events, develop immune mechanisms to counteract this, without any side effects.
People taking part in extreme endurance events especially in the heat and with little training, put their bodies under enormous strain over 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 Ricardo Costa from 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, trigger the body’s immune cells into action,” Costa said.
The 24-hour ultra-marathon study, published in the International Journal of Sports Medicine and the multi-stage ultra-marathon study, published in Exercise Immunology Reviews, both by Costa’s team, reinforces current guidelines for people wanting to take part in extreme endurance events.
These include getting a health check first and developing a training programme that builds fitness and endurance progressively to meet the stresses and strains of the event.
Costa said anything over four hours of exercise and repetitive days of endurance exercise is considered extreme.
“Exercising in this way is no longer unusual – waiting lists for marathons, Ironman triathlon events and ultra-marathons are the norm and they’re growing in popularity,” he said.
“It’s crucial that anyone who signs up to an event, gets a health check first and builds a slow and steady training programme, rather than jumping straight into a marathon, for example, with only a month’s training,” he said.