Former NFL superstar Chris Johnson just revealed he was diagnosed with ALS last year … and the disease has progressed so quickly, he now uses a speech-generating device to communicate.

The 40-year-old Tennessee Titans great and his wife, Brittany, sat down with Michael Strahan on “Good Morning America” on Monday … where the All-Pro running back stated he first noticed symptoms with weakness in his right hand.

After meeting with medical professionals and undergoing thorough testing, Johnson received the news at 39 years old he had Lou Gehrig’s disease … and a doctor recommended medication that might extend his life by a few months, while also suggesting he get his affairs in order.

CJ2K then watched actor Eric Dane and ALS expert Dr. Merit Cudkowicz‘s interview on GMA and decided to make a call … and he said working with her has provided a new approach to fighting the disease.

Johnson is now taking three medications that help slow down the illness and participates in therapy that decreases inflammation, but noted he can no longer hold a cup or lift his daughter.

Shortly after he was diagnosed, he had his voice recorded so he could hold conversations with technology that tracks his eyes.

Johnson praised his wife for taking care of him … and he’s dedicated to fighting the disease, while also raising awareness for ALS and research.

Johnson was the 24th overall pick in the 2008 NFL Draft out of East Carolina … and spent the majority of his career with the Titans. He broke an NFL record with 2,509 yards from scrimmage in the 2009 season.

Johnson made three Pro Bowl appearances and was named Offensive Player of the Year as well.

Despite the health battle, Johnson made it clear the disease has changed what his body can do … but not who he is inside.