Each morning millions of Americans begin their day with a lengthy run, often in the most inclement weather, which some critics of jogging claim borders on obsession.

Millions of others use their lunch hours for a run through smog-choked city streets, or wait until after-work hours for a daily, multi-mile run that they see as a ticket to a healthy body, sound mind and often, an elevated spirituality.But even before President Bush's heart flutter while jogging Saturday, which ended with his hospitalization, many were questioning the wisdom of the obsession of the long-distance runner.

In perhaps the most publicized incident, runner-author Jim Fixx, who wrote the best-selling book "The Complete Book of Running," suffered a heart attack and died at age 52 while jogging in 1984.

Fixx, who became somewhat of a guru for the exercise movement in the early 1980s, ran 60 to 70 miles a week and wrote another running book before his death.

Fixx's untimely death might have been considered the supreme irony were it not for the subsequent death of CBS sports commentator Frank Glieber, who died while jogging at a fitness center.

The facility was owned and operated by Dr. Kenneth Cooper, who wrote a book called "Running Without Fear" which explored Fixx's death and who campaigned to allay fears that jogging might be dangerous after Fixx's death.

Cooper, however, said joggers who suffered ill effects from running were failing to follow guidelines and were not getting proper medical supervision.

"Frank was doing everything opposite to my recommendations," Cooper said. "You can make recommendations but you can't force him to change his lifestyle."

Cooper also warned against overdoing it. "If you run more than 12-15 miles a week, you're doing it for something other than cardiovascular fitness," he said. Bush usually runs two to three miles a day.

Other reports, while studying the dangers of exercise, have mostly exonerated it. Researchers who studied the benefits of exercise against the chance of dying during workouts found while exercise may kill you, not exercising will kill you even faster.

Researchers from the universities of Washington and North Carolina also warned that a little exercise could be the most dangerous choice.

They studied 133 men who had had heart attacks and found for men who worked out under 20 minutes each week, the risk of having a heart attack while exercising was 56 times greater than when they were not exerting themselves. The chances of dying during exercise was lowest by far for men who exercised between 20 and 139 minutes a week.

Other studies suggested that compulsive jogging might be a male version of anorexia nervosa, the potentially fatal condition in which anorexics - mostly young women - starve themselves.

Researchers from the University of Arizona found a strikingly similar profile of characteristics between anorexics and runners.

"Obligatory runners and anorexic women must continue to prove themselves by running or dieting," the researchers warned. They found both groups got "high" through jogging or dieting, were depressed when prevented from running or dieting, and distorted their perceptions in order to continue the activity. Anorexics see themselves as fat no matter how emaciated they become, and joggers run even when injured, they noted.