Frequent strenuous exercise increases the risk of motor neurone disease (MND) in people genetically pre-disposed to develop the condition, according to new research.

Researchers say the pioneering study is a significant step forward to understanding the link between high levels of physical activity and the development of the neurodegenerative disease.

A number of high profile British sportsmen have shared their experience with MND in recent years, including rugby league’s Rob Burrow, rugby union’s Doddie Weir and former Bradford City footballer Stephen Darby.

And previous research has shown an estimated six-times increased risk of MND in professional footballers, the researchers said.

But the team, from the University of Sheffield, has stressed that most people undertaking vigorous exercise do not develop MND and that sport has huge health benefits.

One of the authors, Dr Johnathan Cooper-Knock said: “We have suspected for some time that exercise was a risk factor for MND, but until now this link was considered controversial.

“This study confirms that, in some people, frequent strenuous exercise leads to an increase in the risk of MND.

“It is important to stress that we know that most people who undertake vigorous exercise do not develop MND.

“Sport has a large number of health benefits and most sportsmen and women do not develop MND.

“The next step is to identify which individuals specifically are at risk of MND if they exercise frequently and intensively; and how much exercise increases that risk.”

Dr Cooper-Knock, who is a senior lecturer in Neurology from the university’s Neuroscience Institute, said: “Complex diseases such as MND are caused by an interaction between genetics and the environment.

“We urgently need to understand this interaction in order to discover pioneering therapies and preventative strategies for this cruel and debilitating disease.”

MND, or amyotrophic lateral sclerosis (ALS), affects the motor neurones in the brain and spinal cord that connect the nervous system and muscles to enable movement of the body.

The messages from these nerves gradually stop reaching the muscles, leading them to weaken, stiffen and eventually waste.

MND affects approximately 5,000 people in the UK and the life-time risk of developing the condition is approximately one in 400.

Approximately 10% of MND cases are inherited, but the remaining 90% are caused by complex genetic and environmental interactions which are not well understood.

The Sheffield team say this new research will have a significant impact on the global effort to identify which individuals based on their genetics are at risk of MND.

The aim is to help doctors to be able to offer advice to the families of MND patients about the risks so they can make personal decisions about their exercise habits.

Senior author of the study, Professor Dame Pamela Shaw, director of the Neuroscience Institute and NIHR Sheffield Biomedical Research Centre at the University of Sheffield, said: “The ultimate aim is to identify environmental risk factors which can predispose to MND, to inform prevention of disease and life-style choices.”

Dr Brian Dickie, director of research development at the Motor Neurone Disease Association, said: “In recent years, understanding of the genetics of MND has advanced, but there has been little progress in identifying the environmental and lifestyle factors that increase the risk of developing the disease.

“This is, in part, because the genetic and the environmental studies tend to be carried out in isolation by different research teams, so each is only working with part of the jigsaw.

“The power of this research from the University of Sheffield comes from bringing these pieces of the puzzle together.

“We need more robust research like this to get us to a point where we really understand all the factors involved in MND to help the search for more targeted treatments.”

The findings are published in the journal EBioMedicine,