A MIDDLE-AGED RUNNER had embossed on his T-shirt the statement: "You haven't really run a good marathon unless you drop dead at the finish line," recalls Dr. Edward Colt, medical director for five years of the New York City marathon. One week later, this runner ran what must be considered, by his own standards, the perfect marathon: he dropped dead of an excruciatingly painful heart attack.

Last weekend another middle-aged runner died under tragic circumstances, trudging along a solitary Vermont back road. This runner was Jim Fixx, the 52-year-old author, lecturer and all-round guru on long-distance running.

Fixx's books, "The Complete Book of Running" and "Jim Fixx's Second Book of Running" encouraged many inactive people to get active again, quit smoking, lose weight and organize their lives along more healthful patterns. But along with these sensible suggestions were intermixed advice and beliefs that may have hastened Fixx's death and, I am convinced, may hasten the death of other runners.

Indeed, Jim Fixx conforms to a profile, accepted within medical circles, of the type of runner who is most at risk for death or serious injury. I am speaking now of what psychiatrist Alayne Yates and her colleagues at the University of Arizona Health Sciences Center refer to as the "obligate runner" -- those for whom running is a compulsive drive that preempts fulfillment in other life areas or who run to the point of inflicting physical damage on their bodies.

As many as 25 percent of serious runners may be neurotically attached to their sport, claims Dr. Kenneth E. Callen, associate professor of psychiatry at the Oregon Health Sciences University, in a study published in Psychosomatics, the journal of the Academy of Psychosomatic Medicine.

First, the obligate runner takes up serious running -- defined as more than 40 miles per week -- relatively late in life as compared to other athletes. Jim Fixx, for example, was 35 when he started. Most obligatory runners "become unequivocally committed to running in the third to fifth decade of their lives," wrote Yates and her colleagues in the Feb. 3, 1983 issue of The New England Journal of Medicine.

Second, obligate runners are found among those who generally feel unfufilled in their professional or personal lives and use running as a method for achieving meaning. In this area, too, Fixx fits the profile.

Despite impressive professional accomplishments (managing editor at Horizon, excutive editor at McCalls), Jim Fixx's sense of direction as well as his greatest life satisfaction date from his discovery of running. In his books and lectures, he offered his readers a similar enlightenment by promising to "show you how to become healthier and happier than you ever imagined you could be." Nor was Fixx's enthusiasm insincere. To Fixx, running was an activity that could "change your life" and, in his case, it did.

Third, obligate runners use running as an aid towards the denial of aging, physical dissolution and death. In the survey published in the February 1983 issue of Psychosomatics, Callen described the typical runner likely to wind up hurting or killing himself: a middle-aged man tortured by the prospect of growing old, troubled by diminished physical attractiveness and bored by the absence of job or marital fulfillment.

In their attempts to understand the personality traits common to obligate runners, the psychiatrists at the University of Arizona discovered important similarities with anorexics. "The runners in our sample shared many of the qualities of the anorexic patient," wrote these doctors in their paper, "Running -- an Analogue of Anorexia?" published in The New England Journal of Medicine. "They were generally self-effacing, hard-working, high achievers from affluent families who were uncomfortable with anger and who characteristically inhibited the direct expression of affect (mood). Their singular commitment to running occurred at a time of heightened anxiety, depression and identity diffusion."

This "grim asceticism" mentioned by these authors elsewhere in their paper can be confirmed by anyone who takes the trouble to observe the pained, but stoic, faces of obligatory runners when they perform their rituals on our city streets and country byways. Observing these runners, it's hard to escape the conclusion that many of them are attempting to discover who they are and who they want to be via running.

"The heightened commitment to sport or diet provides the runner and the anorexic with a clear identity in that it differentiates them from other less dedicated people," writes Yates and her colleagues.

Another characteristic of the runner at risk for disaster is a tendency to think of running in quasi-mystical, even irrational terms. "It is here with my heart banging against my ribs that I discover how far beyond reason I can push myself. Furthermore, once a race has ended, I know what I am truly made of. Who can say how many of us have learned some of life's profoundest lessons while aching and gasping for breath?" wrote Jim Fixx.

Such a monomaniacal search for identity and perfection, Yates and her colleagues discovered, is characteristic of the obligate runner. "Assuming an identity as a runner served an adaptive function, providing a sense of self, a feeling of control over internal and external circumstances, a difficult but obtainable goal." In most cases, attaining a goal is less important than the continued effort to achieve it. "The goal itself is entirely secondary and is reset at will to rationalize continuation of the process."

Eventually such "dedication" and "commitment" leads to behavior that one could be forgiven for labeling as simply "addictive." When questioned whether or not running was an addiction, Jim Fixx had this to say: "It's a question of definition . . . . Take me. I run every day and some people call that crazy. They say, 'It's taking over your life.' But I think it's just great."

Most obligate runners would agree. Indeed, this helps to explain why sports clinics are besieged by requests for anti-inflammatory drugs, orthopedic devices and psychological techniques aimed at bolstering the obligate runner's determination to deny and ignore painful experiences.

"To acknowledge an injury and stop running is intolerable to them (the obligate runners) because it proves what they have feared facing all along -- their own vulnerability," according to Michael H. Sacks, associate professor of psychiatry at Cornell University Medical College, who specializes in treating runners and running-related problems.

In the case of Jim Fixx, it stretches medical imagination to think that he did not have chest pains or some other forewarning of his heart attack.

The obligate runners' flight from vulnerability is rendered socially acceptable as a result of misguided but widespread attitudes concerning how runners should respond to physical pain. The runner, mentioned earlier, who literally ran himself to death in the presence of excruciating pain, is an extreme example of a process many obligate runners are putting themselves through every day: run that extra mile no matter how it hurts, break through the "wall."

In a 1982 article in Sports Illustrated, long-distance runner Alberto Salazar is described as "possessed of a certain pride" because he was willing to run 105 miles a week on a stress fracture -- tiny bone cracks caused by pounding the pavement. In one marathon, he pushed himself into heat prostration. When his body temperature reached 108 degrees, he was packed in ice and administered the last rites of the Roman Catholic Church. Fortunately, he survived. How many other lesser-known runners have died because they, too, were "possessed of a certain pride"?

Concerning the emotional health of runners, Oregon psychiatrist Callen has this to say of his large sampling of 494 runners: "Twenty-five percent state that they have experienced emotional problems associated with running. In almost every instance, the problems is one of depression, anger or frustration associated with not being able to run due to an injury."

Yates and her colleagues noted a similar pattern: "When the obligatory runners in our sample were unable to run, they experienced depression and anxiety about physical deterioration. Not surprisingly, they continued to run in spite of illness, which was often denied, or contraindications, such as arrythmias, atherosclerotic heart disease or stress fractures. Such unreasonable dedication has resulted in permanent disability or even death."

Other obligate runners -- apparently Fixx was in this group -- fail to seek medical opinion despite the fact they have reason to believe that they might be genetically predisposed to coronary disease or other health problems. Fixx's father had a heart attack at the age of 35 and died of heart disease at 43. Nevertheless, Fixx last December adamantly refused to take a stress test even though it was pressed on him at the Aerobics Center in Dallas.

This failure to seek help is particularly tragic since many of these people could now be treated by coronary bypass surgery.

Already, Fixx's tragic death has been written off by some as a coincidence. Perhaps he would have died earlier if he didn't run regularly. No one can "prove" that running killed him. But such statements fail to address the fact that, on the average, the contemporary American male doesn't die at 52, even when he weighs too much, underexercises, smokes excessively or, within lmits, otherwise abuses his body.

The death of Jim Fixx can and should lead to a reexamination of the value and wisdom of running in the 40-80 mile per week range. This is particularly true for runners who during their first 25 years led comparatively sedentary lives.

At the very least, one point appears unarguable: Obligatory running does not protect against the onslaught of serious cardiovascular disease.

Only six years ago a physician and authority on marathon running declared: "When the level of vigorous exercise is raised high enough, protection from coronary heart disease appears to be absolute." Based on the unfortunate experience of Jim Fixx, we now know that this is nonsense.

It's time to put running in its proper perspective: an acceptable, although often tedious exercise which can confer benefits when carried out in moderation and within the bounds of common sense.

But running doesn't make anybody immortal. It doesn't bestow or confirm identity. And it can't infuse meaning and purpose into lives that are otherwise unfulfilled.