Tim Green’s days are full.

The former linebacker and defensive end for the Atlanta Falcons, who in retirement has practiced law, worked as a commentator on NPR, hosted TV shows and written more than 20 books, spends his mornings tackling his emails. After that, Green, 57, works through a series of conference calls and law firm business through the middle of the day, then he writes all afternoon until it is time for what are often extended family dinners.

Green watches his grandchildren play until their bedtime arrives, then he watches TV with his wife, Ilyssa, and youngest son, Ty, 15, before reading himself to sleep.

And Green does all this while having amyotrophic lateral sclerosis, also known as A.L.S., or Lou Gehrig’s Disease, the degenerative nervous system disorder that causes the loss of muscle control, getting plenty of assistance at every turn.

A ventilator keeps him breathing. He eats with a feeding tube. He cannot speak. He communicates and writes using a device that tracks his gaze as he selects letters on a screen to create messages that the device types out for conversations, or as a chapter in his next book. His latest, “Final Season,” about a family grappling with whether a child should keep playing football after his father, who is also his coach, is diagnosed with A.L.S. — yes, it is based on true events — debuted recently at No. 1 on The New York Times’s best-seller list for children’s middle grade hardcover.

“It takes immense patience, even now, when I’ve been writing several hours a day, six days a week, for three years,” Green said of the laborious process during a video interview last week. The swoosh of his ventilator hummed through the airwaves every few seconds. “This machine is beautiful, but temperamental. When I had the use of my fingers, this book would have taken me less than a year to write.”

To see Green in this state, to hear that powerful tenor voice that once melodically coursed over public radio airwaves transformed into halting, computer-generated sentences, to look at a former wrecking ball on the football field nestled practically motionless in the high-tech chair that allows him to function, is a reminder of the disease’s cruelty — and of the nimble mind still seeking to make the most of a body that can no longer survive without constant assistance.

Green has sustained a rewarding existence by carefully managing the disease with the aid and intervention of the latest medical technology. He can still write, and practice law, and be a husband, and father to his five children, and grandfather, and football fan, even though he believes his A.L.S. was caused by the game he played for so many years.

Brain injury experts and neurologists have performed extensive research on whether repeated blows to the head from contact sports can significantly increase the risk of A.L.S., hasten its onset, or even lead to another disease with very similar symptoms. While research continues, Green has no further questions on the matter.

“My A.L.S. doctor is Merit Cudkowicz, one of the most highly regarded authorities on A.L.S. in the world,” he said. “If she says repeated blows to the head caused my A.L.S., then that’s what caused it.”

One of Green’s sons, Troy, said his father’s life can be divided into two distinct phases.

The first was built around physicality. Green was a star at Syracuse and a first-round N.F.L. draft pick in 1986 who played eight seasons with the Atlanta Falcons. His chiseled bone structure and deep-set eyes did not hurt his efforts when he launched his television career. At home, he got on all fours and his children rode around the house on his back like he was a pack horse.

In his second phase, Green pursued a legal career and work as an author following his retirement from the N.F.L. in 1993. Green first started struggling with his hands and fingers around 2011, but he was not diagnosed with his slowly progressing form of A.L.S. until 2016. A.L.S. is not a subtle condition. Before long, he was coping with slurred speech, trouble walking and even breathing.

Green despaired at what lay ahead — brutal decisions about whether to get hooked up to ventilators and feeding machines — but Troy convinced him that what the family needed from Tim had little to do with how his body functioned.

“His soul and his brain,” said Troy, who is 27 years old. “That is what we love and call Dad.”

These days, the disease does not cause Green all that much pain other than the bronchial suctioning he has to endure because his lungs can’t clear fluid, and the necrosis (the death of body tissue) in his right foot and shin that can make them feel like they are on fire. Other than on rainy days, when falling barometric pressure can take its toll, old football pains in his knees, shoulders and neck do not ache as they once did because he no longer uses them.

His mental health is another matter. Green forces himself to focus on what he still has, and his memories of what he used to.

He said when he wakes in the morning, he tries to first be grateful for another day with his family, friends, and those around him. He gives thanks for the close-knit nature of his family life, with several of his adult children living in homes steps away from his, and for the nearby lake, “the hills, the trees, the birds, blue sky, clouds, wind, rain and snow. And the sun, moon, planets and stars.”

At the dinner table, he watches his family eat and conjures memories of tasting fresh tomatoes and bacon and red sauce over pasta and sausage, “and a fat glass of Caymus Cabernet.”

Sometimes, the power of those memories becomes overwhelming and the tears flow. But mostly, there is solace in the routines that dominate his life, though even those can have their challenges.

The family real estate business that Troy largely runs has had to work hard this year to address maintenance and safety complaints about its management of several of its low-income housing properties in upstate New York.

And, of course, there was the tension that formed “Final Season.” As his A.L.S. worsened dramatically three years ago, the family argued over whether Ty should continue to play football on his local youth team. Tim and some of his sons felt that because practice routines and tackling techniques have changed during the past 20 years, Ty, who was then 12, could continue to play safely. Ilyssa wanted football out of Ty’s life. He now focuses most of his athletic energy on lacrosse.

Tim Green said he does not regret his own football career. He remains a fervent fan who watches games all season, especially the Falcons, missing nearly everything about his playing days.

“The TV cameras, the uniforms, the colors, the pageantry, the smell of fresh air spoiled by sizzling dogs, spilled beer, fresh tape, and cut grass, the crowds, their cheers andtheir boos,” he said, ticking off details of a life still fresh in his mind. “The paychecks, fast cars, the bursting joy on the face of a kid, and all you did was scribble your name on his cap. The joys are endless.”

So, too, are the consequences. All of it makes for a good story.