Motor Neurone Disease is a muscle wasting condition that can affect anyone from pensioners to professional footballers.
But now researchers believe it may also be associated with higher levels of fitness.
MND is a disease of the motor neurones, the lines from the brain which connect to the muscles and command them to move and grow.
When these lines are cut by the disease the muscles cease moving and waste away.
A few years ago Italian research suggested that footballers were prone to developing MND.
Willie Maddren and MND
A British footballer who developed the disease was Middlesbrough player Willie Maddren.
Willie Maddren died almost seven years after the first symptoms of MND appeared. He always had his suspicions that his condition could be linked in some way to his football.
So how likely is it that playing football is linked to MND?
Dr Kevin Talbot, Reader in Clinical Neurology at Oxford University, says, "I think there is a gathering of opinion that there is perhaps something there. I think the key thing is that it's an association so it's not necessarily playing the football that causes the disease
It's some association between being fit and a small increase in the disease."
At the moment we have a series of clues but not the complete story.
Brian Morrin from North East England used to be super fit but three years ago he developed calf problems and weakness in his shoulder.
After completing his second Coast to Coast cycle run, he was told he had a muscle wasting condition.
Later it was diagnosed as Motor Neurone Disease - or MND.
Within a few months the man who trained with 100 kilo weights could barely lift a few pounds.
Brian's focus is now on making the most of the time he has left, and preparing his family for what's to come.
The full story will be featured on BBC Inside Out North East & Cumbria on Monday 22 February at 1930 on BBC One and BBC iPlayer.
BBC Inside Out