A former youth-league football coach on trial in Montgomery County on child sex abuse charges testified yesterday that he developed a close friendship 10 years ago with one of his players, but emphatically denied any sexual improprieties.

"Absolutely not," John Stuart Mackintosh responded when asked if he had fondled or touched improperly a 14-year-old youth during weightlifting workouts at a weekend outing in Western Maryland and at his Silver Spring apartment.

Mackintosh, 51, is charged with child sexual abuse stemming from a series of alleged incidents between January 1981 and March 1982. At that time, Mackintosh was the head football coach for Catholic Youth Organization teams sponsored by St. Camillus Church in Silver Spring.

Mackintosh, who now lives in Laurel, has been football coach at Pallotti High School in Laurel since 1983. After his arrest last June, he gave up that post pending the outcome of his trial.

The alleged victim, now 24, testified Wednesday that Mackintosh massaged and fondled him after showers at the coach's apartment. The man, whose name was withheld to protect his family, said Mackintosh also took nude photographs of him. He said he decided to tell authorities about the alleged abuse after recent extensive therapy sessions.

Also yesterday, the alleged victim's older brother testified that he saw Mackintosh fondling his brother while the latter was lifting weights in the church basement. On cross-examination, the older brother, who has also accused Mackintosh of sexual abuse, said he had told authorities only on Monday of what he had seen.

Mackintosh, appearing relaxed, repeatedly denied all the allegations yesterday during more than three hours on the witness stand. More than 20 supporters, friends and Pallotti football players listened in the gallery.

Mackintosh, a management analyst with the federal government, said he had coached about 2,100 boys and girls during 24 years at St. Camillus and that his football teams had won 14 youth football championships. He described himself as an affectionate, caring coach who had invited more than 200 youths to his home and frequently arranged weekend outings for players.

"I am the type of person to have my arms around people, pat them on the back, hug them. I'm a hugger," he testified.

Mackintosh testified that the alleged victim often came to his apartment after weightlifting practices, but that he never massaged the youth's body or saw him nude.

"He would take a shower, get dressed and we would go wherever . . . usually to get something to eat," Mackintosh said. To relieve sore muscles, Mackintosh said he sometimes "rubbed the neck and arms" of the youth for a few minutes, but did not touch him below the chest.

Mackintosh said that during a trip to Deep Creek Lake in Western Maryland in March 1982, he slept in the same bed with the youth after the teenager and a friend became frightened by unknown noises. But Mackintosh denied allegations that he had fondled the youth in the bed.

In September 1982, Mackintosh said the youths' parents called him and told him to stay away from their two sons. Mackintosh said he was hurt and shocked by the allegations and the youth's rejection. "In all my years of coaching young men, I had never had one to say he didn't want to see me again," Mackintosh said he wrote in a December 1982 letter to the youth.