Tired? All in the mind, says sports scientist

Physical exhaustion is all in the mind, according to new research. A British scientist and would-be Olympic rower has discovered that the mind decides the body is fatigued long before muscles really are tired.

Physical exhaustion is all in the mind, according to new research. A British scientist and would-be Olympic rower has discovered that the mind decides the body is fatigued long before muscles really are tired.

Paula Robson-Ansley, of the University of Portmouth, has found that the brain takes its cue from blood levels of a "signalling" molecule called interleukin-6 (IL-6) to tell the body it is tired, so that muscles are not exercised dangerously hard. Yet muscles could work for longer if the brain could ignore the "tiredness" signals.

But the discovery could also have a dark side: endurance athletes of the future could use drugs that would block the brain's reaction to IL-6 to go beyond their normal pain and exhaustion barrier.

Dr Robson-Ansley injected seven club-standard runners with either IL-6 - at levels equivalent to having exercised for an hour - or a dummy drug, and recorded their times over 10 kilometres. A week later, the experiment was reversed.

On average, reports New Scientist magazine today, the athletes ran nearly a minute slower after receiving IL-6. "These were people whose times would normally only fluctuate by five seconds," said Dr Robson-Ansley.

Other research has shown that blood levels of IL-6 are 60 to 100 times higher after prolonged exercise. Even people at rest who receive IL-6 injections report feeling more tired.

Besides athletes, the finding could help treat people with conditions such as chronic fatigue syndrome. Oone company is testing a "blocker" antibody for chronically fatigued patients.