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New study investigates links between fatigue, genes and athletic performance

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The ground-breaking research may also explain Unexplained Underperformance Syndrome (UPS) - the phenomena where very fit and mentally prepared athletes perform poorly for a substantial period of time for no apparent reason, or follow up a world class performance with a period of markedly substandard ones a short time later.

The study undertaken by Dr Paula Robson-Ansley and her research team from the University of Portsmouth’s Department of Sport and Exercise Science involved taking blood samples from 80 athletes during the 2006 Merida TransWales Mountain Bike Race where mountain bikers covered more than 500km over rugged and hilly terrain in seven days.

Blood was also taken from 85 people around the UK who have been diagnosed with Chronic Fatigue Syndrome (CFS).

Dr Robson-Ansley suspects that ‘fatigue resistant’ athletes may carry a different form of a gene compared with CFS sufferers that makes them less likely to suffer excessive fatigue during and following endurance type exercise.

The tests looked at Interleukin-6 (IL-6), a messenger molecule in the body that is released when the body is under stress - for example, during infection or illness or when blood sugar levels get low by sending a ‘distress signal’ to the brain. The IL-6 molecule and its soluble receptor need to work together for the brain to receive the message.

The brain, having received this message from the IL-6 molecule and its receptor, then sends out commands to slow the body down to conserve energy and rest.

Previous studies had found that IL-6 levels in athletes dramatically increase during prolonged exercise - one study found IL-6 levels increasing 100-fold in runners following a marathon. In a prior study, Dr Robson-Ansley found that by artificially elevating levels of IL-6 in trained runners they ran markedly slower during a 10 km run trial.

But Dr Robson-Ansley’s latest research looks at whether ‘fatigue resistant’ endurance athletes have a slight variation of the gene responsible for IL-6. Previous studies have found that people a C-type variation of the gene produced less IL-6 during infection than those with the G-type of the gene.

“The findings of these tests may be significant in furthering our understanding of the relationship between fatigue and athletic performance and why some people develop chronic debilitating fatigue for no apparent reason,” Dr Robson-Ansley said.

“But one has to be cautious in prescribing the role genes might play in athletic performance as it is still very early days. The history of sport is littered with countless examples of athletes who succeed against all kinds of odds - including physical ones.”

Dr Robson-Ansley’s study also looked at changes in the levels of the IL-6 receptor - the receiver molecule that helps send the message to the brain - over the course of the mountain bike event. Blood samples were taken every morning at 6am before the cyclists completed that day’s stage of the race.

The study found that the IL-6 receptor levels in athletes markedly increased over the seven-day mountain bike event as the mountain bikers became more tired. But IL-6 levels did not change. This, Dr Paula Ansley-Robson said, might suggest it was not an increase in IL-6 that was making athletes tired but, rather, an increase in the levels of the IL-6 receptor.

“This is a very interesting finding as I published a paper in 2003 where I hypothesised that the chronic fatigue those athletes with UPS report may be due to an increase in the receptor molecule during or following exercise,” Dr Robson-Ansley said.

“This would heighten the athlete’s sensitivity to IL-6 when it is produced i.e. during exercise or illness, resulting in an exacerbated fatigue and worsening of athletic performance.

“Previous laboratory studies have found that the IL-6 soluble receptor amplifies the sensation of fatigue in rats with high IL-6 levels. Human studies have found that if you block the IL-6 signaling by giving an antibody which blocks the receptor then the sensation of fatigue caused by very high levels of IL-6 instantaneously disappears.

“We need to do more work in this area, but I think we now know that there is a lot more going on in the relationship between the IL-6 receptor and fatigue than previously thought.”

The results of the new study are expected to be released in mid-2007.

Dr Robson-Ansley is a former Olympic standard rower. She suffered from chronic fatigue syndrome and retired from the sport to focus solely on her academic career. But she has continued to work with elite sportsmen and women around the world, running clinics for exhausted athletes in South Africa and the UK.

Rajiv Maharaj | Quelle: alphagalileo
Weitere Informationen: www.port.ac.uk

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