Former NFL star Chris Johnson diagnosed with ALS

"There's no history of ALS in my family," Johnson told Michael Strahan as he was using a speech-generating device based on recordings of his voice to speak. "My doctors believe my case is what's called sporadic ALS, which is actually how the vast majority of ALS cases happen.

"That's one of the reasons this disease can be so shocking. It can happen to someone who never expected it."

Johnson played 10 seasons in the NFL, split between the Tennessee Titans (2008-13), the New York Jets (2014), and the Arizona Cardinals (2015-17). During the 2009 season, in which he was named the Offensive Player of the Year, Johnson set the NFL record with 2,509 yards from scrimmage, including 2,006 of those on the ground. 

Now, the 39-year-old is in the fight of his life because ALS is a progressive disease that attacks nerve cells that control muscles throughout the body. It became commonly known as Lou Gehrig's Disease after the New York Yankees baseball player got the disease in 1939 and was forced to retire. Currently, there is no known cure. But Johnson is going to battle as he's currently in a clinical trial as part of the treatment he's been receiving.

"Honestly, I don't know if you ever fully process it," Johnson said of the disease. "At first, you're in shock. Then you realize you have two choices. You can give up, or you can fight. I chose to fight."

Despite what is happening, Johnson remains upbeat and the same guy who set the NFL on fire with his breathtaking speed.

"I want people to know that I'm still me," Johnson said. "ALS has changed what my body can do, but it hasn't changed who I am. People sometimes look at the physical disability and assume you're not still the same person inside. I still think the same. I still dream. I still love my family. My body just doesn't cooperate."