Hands tell the story in “On Freddie Roach,” a six-episode documentary series beginning on Friday on HBO. The flashing fists of young boxers in the ring move in counterpoint to the trembling fingers of Mr. Roach, a trainer and former fighter who now does battle with Parkinson’s disease.

They come together in a scene that partly redeems that hoariest of boxing-movie clichés, the prefight taping. Mr. Roach, who has been betrayed by his own hands, slowly and laboriously prepares those of one of his young fighters, Amir Khan, for a title bout. As he applies the long strips of tape to Mr. Khan’s fists, he pauses to dangle his arms and shake out the tremors.

In most cases you would expect a reality show centered on a high-profile Hollywood gym (headquarters for the superstar Manny Pacquiao), run by a celebrity trainer with a potentially debilitating illness, to capitalize on the tawdriness and sentimentality that are hard-wired into the story and milieu. “On Freddie Roach” doesn’t ignore them: in one scene, as Mr. Roach walks through a Las Vegas hotel lobby with Mr. Khan’s entourage, a buxom young woman exposes her breasts, driven by the celebrity wattage or the film crew or both.

The heart of the show doesn’t lie in exposé or sensationalism, however. It’s in observation and vérité technique, explicitly inspired by Frederick Wiseman, whose documentaries have been cited as a model by Peter Berg, an executive producer of “On Freddie Roach.” (No one is credited for directing the individual episodes, and it seems safe to assume that Mr. Berg largely filled that role as well.) Technically there is no narration, though extracts from interviews with Mr. Roach, heard in the background, often serve that purpose.