United Kingdom, June 29 -- Former NFL running back Chris Johnson has been diagnosed with ALS and has lost the ability to speak.

The 40-year-old sportsman was diagnosed with the progressive neurogenerative disorder last year, after showing certain symptoms such as weakness in his right hand which he and wife Brittany initially put down to wear and tear from his football career.

Speaking on Good Morning America, Chris said: "At first it was little things like my grip didn't feel right, and I wasn't as strong as I'd always been."

Brittany added: "I thought because of football and his career that it has to be something with that. Maybe a pinched nerve or something along those lines, but never ALS."

But after a string of tests, Chris - who...