NEW YORK (AP) — Football star Steve Gleason was known for throwing caution to the wind. He'd launch himself down the field with seemingly no regard for his own well-being.

Gleason cemented his place in New Orleans Saints lore with a blocked punt during the Louisiana Superdome's reopening following Hurricane Katrina. He retired from the sport in 2008, saying: "I can walk away with my health."

Fate had other plans.

You'd better have plenty of tissues on hand when you watch the moving, remarkable "Gleason," a documentary about the ex-Saint whose bravest days were actually ahead of him.

Five years to the day after his memorable block, Gleason went public with his diagnosis of amyotrophic lateral sclerosis, also known as Lou Gehrig's disease. Doctors said he had only a few more years to live. Adding to the anguish of the moment was that his wife was pregnant with their first child.

Clay Tweel's documentary could so easily have turned into a gooey pile of Hallmark aphorisms but it refuses to be maudlin, faithfully capturing the unmerciful progression of the disease as it robs Gleason of his voice, the use of his legs and later control over his bowels. It never robs his spirit, though.

The footage is mostly shot by Gleason himself in the form of an ongoing video diary to his newborn son, Rivers. He wants to give advice, read nursery books and tell him who his father is before he runs out of time. Gleason comes across as irrepressibly optimistic, even as his body turns on him. He's as fearless as when he was playing.

Tweel (whose other documentaries include "Print the Legend" and "Finders Keepers") includes interviews with family members and friends, but stumbles when he strays further afield — like interviews with members of Pearl Jam, Gleason's favorite band.

Tweel occasionally adds piano or classical music to signal poignant moments, as when Rivers happily eats cake with his hands at his first birthday while his father beside him in a wheelchair needs to be fed. The best footage is the kind that's unanticipated, as when cameras capture a marital spat or a spontaneously dad-son nuzzle.

Gleason tries to outwit his disease at every turn. He believes technology like eye-tracking software can give back to ALS patients whatever the disease robs. But it's a brutal illness. Within a year, Gleason starts to walk awkwardly, then needs a cane, then a wheelchair. Subtitles eventually are added, as if he was slowly slipping into a foreign land.

"I think the last of my talking days are here," he addresses his son at one raw point. "I have no hope. I want to punch something but I can't. The only thing I can do is scream."

The former football play's humor, though, won't be dulled. One of the film's most enduring images is of Gleason zooming along in his wheelchair with his gleeful infant son in his lap. Gleason even keeps upbeat while undergoing a painful enema.

While struggling against the disease and advocating for fellow ALS patients, Gleason is also trying to heal the rift with his own stern father and deliver wisdom to the next generation. It's a movie as much about fathers and sons as it is about living with ALS.

It's also a moving portrait of grace under pressure for someone else in the home — artist Michel Gleason, his wife. Her life now is unspeakably hard, caring for two people at the opposite ends of life. One needs his tracheotomy wound cleaned, the other needs his boo-boos kissed. Both need their diapers changed.

She shares her husband's can-do, free spirited energy, but the film reveals the strain, as when she re-watches her marriage video while her husband and newborn slumber. There is something like terror in her eyes. "I am wearing u down to bones," he writes to her later.

The tissues will pile up — there's so much tender and funny footage that it spills over into the end credits — but "Gleason" is worthy of the tears. It's exactly what Gleason says about his own life: "It's not going to be easy, but it's going to be awesome."

"Gleason," an Amazon Studios release from Open Road, is rated R by the Motion Picture Association of America for language. Running time: 110 minutes. Four stars out of four.

___

MPAA Definition of R: Contains some adult material. Children under 17 are required to have a parent or guardian accompany them.

___

Mark Kennedy can be reached at http://twitter.com/KennedyTwits