WHY ATHLETES are more likely to need pacemakers in old age.

Dr Alicia D’Souza, from The University of Manchester and first author on the paper, said: “The heart rate is set by the heart’s pacemaker, but this is controlled by the nervous system. The ‘vagal’ nerves lower the heart rate and therefore it was assumed the low heart rate of athletes is the result of over activity of the vagal nerves.

“But our research shows this is not the case. Actually the heart’s pacemaker changes in response to training and in particular there is a decrease in an important pacemaker protein, known as HCN4, and this is responsible for the low heart rate.”

The researchers say these molecular changes in the sinus node – the cardiac structure responsible for generating heart rhythm – may help us to understand the more frequent occurrence of heart rhythm disturbances or even loss of consciousness in athletes.