ARE ATHLETES NEAR THE LIMIT? : BREAKING TRACK AND FIELD RECORDS WILL BE RARE IN NEXT MILLENNIUM.

Byline: Barbara Huebner Boston Globe

In 40 days Michael Johnson attacked the world record for 200 meters, a mark that had stood for 17 years, and lowered it twice: from 19.72 seconds to 19.66 in the U.S. Olympic Trials, then to a mind-boggling 19.32 in the Olympic Games.

As if that weren't enough, Johnson said the next afternoon that a tiny stumble on his fourth step had slowed him on his way to demolishing the record. ``I really have to believe that I can run faster than what I ran out there last night because of the fact that it wasn't a perfect race. So I would hope that I could break it sometime soon,'' he said.

Johnson's pace in the 200 was faster than Donovan Bailey's in his world record for the 100 meter dash, set just five days earlier. Just as impressive, a New Zealand statistician in 1984 had projected that no one would run a 19.32 in the 200 until somewhere around the year 2026.

And there was Johnson, sure that he can run faster still. Records are made to be broken, the saying goes, and historically they have been. But with some of the speeds being attained, distances jumped and weights lifted these days, some are beginning to wonder how much longer improvements - which athletes, coaches and spectators all have come to expect - can be made. Are there no limits?

Certainly there are. Although it depends on how you define certain, as well as how you define limits.

``Michael would know better than anyone else whether he can go faster,'' said Peter Snell, Olympic gold medalist at 800 meters in 1960 and 1964, who twice held the world record for the mile. But for the most part, breaking world records ``is going to be a very uncommon event in track and field in the next millennium,'' predicted Snell, who is now an exercise physiologist at the University of Texas Southwestern Medical Center in Dallas.

In track and field, as well as most other sports, several factors help determine the limits of human potential, and not all of them are human at all.

Physiology: As we now know it, the human body can run only so fast, jump so high, throw so far.

``The primary thing that makes an athlete is genetics,'' Ann Grandjean, chief nutritional consultant to the US Olympic Committee, said in an interview.

For instance, most successful sprinters have an abundance of fast-twitch muscle fibers, which contract and relax quickly, and legs that are long in relation to their torso for greater stride length. For any athlete, even the ability to train at high levels of intensity without repeated injury and time off for recovery is at least partially determined by genetics.

Gideon Ariel, founder of Ariel Dynamics Inc., and formerly an adjunct professor of computer science at the University of Massachusetts-Amherst, watched Johnson in Atlanta. ``Basically his stride length is about 20-30 centimeters shorter than his opponents', but his stride frequency is much higher,'' he said. ``This means he is in contact with the track longer, and that gives him an advantage, like having a bigger propeller on a boat.''

Then there is the matter of knowing how to make the best use of those genetic gifts. Ariel has been studying the biomechanics of elite athletes since the late 1960s, using ever-more sophisticated computer techniques to analyze such factors as force, angle of joints, acceleration and velocity. A slight adjustment in the speed of the non-jumping leg before liftoff in the long jump, for instance, could make the difference between winning an Olympic gold medal or going home empty-handed.

In 1976, Ariel projected the outer limits of athletic performance in four track and field events. No one is ever likely to run 100 meters in less than 9.6 seconds, he said, because greater speed would probably tear muscles, if not break bones. Others have predicted that the 100 will be run in 9.15 seconds sometime after the year 2100, but these projections are based on current statistical trends, rather than physiology.

Bailey's newly set record is 9.84 seconds. In the past 10 years, the record for the 100 has been lowered six times, starting at 9.95, but only once by more than two one-hundredths of a second. So even the most conservative of projections appears safe for decades.

As for the mile, Snell believes that world-record holder Noureddine Morceli of Algeria, at 3 minutes, 44.39 seconds, is bumping up against the ultimate possibilities for that distance.

``The name of the game in mile-running is to be able to produce enough energy to maintain your running speed,'' he said. ``The rate of energy production is very largely dependent on the rate of oxygen getting to the working muscle. Those muscles utilize oxygen for a chemical reaction to produce energy. So a

limiting factor is the delivery of oxygen.''

Snell said he doubts that training will make big inroads in that area, ``so we're sort of left with not much room for improvement.''

But several specialists caution that evolution might give a boost to record-breaking. Projections are based on what we know now of the body's limits, and the average body at that. ``There will be new human beings, taller and stronger, who will probably be able to do better,'' said Ariel.

Not only could someone be born tomorrow with a combination of genes better suited to an event than we have yet seen or imagined, someone could well exist already, undetected. `` There's probably a lot of talent around capable of gold medal stuff but they don't know it. Maybe we'll come up with some identification of people who have absolutely the best genetic capacity'' for breaking records, said Snell.

Equipment: Hard surfaces such as the Mondo track in the Atlanta Olympic Stadium promote faster times, because the return of energy into the leg with each stride is greater - little is lost by the foot's sinking into the surface, the way it would in dirt, cinders or even a softer synthetic track. Improvements in the cushioning and stability of running shoes, the flexibility of vaulting poles, the fabric and fit of swimsuits and speed skating skins, the degree of wash absorbed by lane markers in a pool - all contribute to faster times. Although most observers believe the largest gains in these areas have already been made, no one is ruling out some unforeseen product or invention.

Conditions: Sprinters love hot, humid weather, because it keeps their muscles looser. Distance runners prefer it cooler. Performances in track and field tend to be better at higher altitude, because of less wind resistance, and athletes who train at altitude see an increase in red blood cells, and thus the ability for oxygen to be carried in the blood, that carries over for awhile to performance at sea level as well.

Training and technique: For years, weight training for anyone but weight lifters was shunned, as athletes and coaches feared the extra muscle would result in slower performances. Now even marathoners understand the benefits of a strong upper body, to maintain form and minimize fatique.

Periodization - varying the cycle of training so an athlete peaks for a major event - is relatively new. In general, athletes now start with a period of relatively high volume (a lot of miles running or swimming, for instance) at a lower intensity (or speed), dropping the distance and increasing the speed as the event date nears.

Steven Fleck, an exercise physiologist and former head of physical conditioning for the US Olympic Committee, says periodization ``is one area in which a lot of improvement can still occur.''

Engineers at the USOC and elsewhere are continually seeking ways to electronically monitor the form and strength of athletes in a variety of sports, from archery to swimming. In the latter, Amy Van Dyken, who failed to qualify for the 1992 Olympics but went on to win four gold medals in Atlanta, trained for several weeks at the USOC facility in Colorado Springs strapped into a tow system that measured water resistance while she was being filmed by an underwater camera.

Van Dyken used the system in two ways, said Tom Westenburg, senior design engineer of the development lab there. She could either be towed along at a rate 5 to 6 percent faster than her usual pace - ``to experience what it's like to swim faster without having the ability yet'' - or she could take advantage of a tow to just try out new positions and attempt to streamline her stroke.

``I don't want to take credit for her hard work,'' said Westenburg. ``We're just kind of polishing a finely-tuned machine here.''

Psychology: Perhaps the least measurable but most wide-open factor. ``It's the last frontier area in which great breakthroughs will be made,'' said Dr. Jim Loehr, president and CEO of LGE Sports Science in Orlando, Fla., which works with athletes. ``The greatest breakthroughs people make are often associated with changes mentally and emotionally.''

Advances in brain scanning, for instance, give a clearer picture of how such techniques as visualization and imagery actually work, he said.

Loehr, who worked with the speed skater Dan Jansen before the 1994 Olympics, said Jansen was reluctant to even write down one of his most-yearned-for goals, to break 36 seconds for 500 meters. ``For 10 years he had failed, and he didn't want to fail again,'' Loehr said. He said he told Jansen, ``If you really don't set it out there and treat it as reachable, for sure you will end your career without reaching it.''

So every day Jansen wrote at the top of his training log: 35.99. In the months leading to his retirement, he broke 36 seconds three times: twice at 35.99 and once at a blistering 35.76. ``It was inconceivable, beyond what anyone could ever imagine,'' Loehr said.

Something like breaking the four-minute mile for the first time. When Roger Bannister ran 3:59.4 in 1954, it redefined what many saw as the limits of human potential. Seven weeks later, the record was broken again and within a few years four minutes had been breached dozens of times. Once one person overcame the barrier, others realized it could, indeed, be done.

``It's pretty hard to say what is a limit and what's not,'' said Loehr, who added that athletes need to concentrate on reaching their own potential, not on beating someone else. But if you're Michael Johnson, who is setting the standard for what is possible at 200 meters, every time you better your personal performance you're also redefining the standard.

``He can go faster, there's no question about it,'' says Ariel of Johnson.

Snell adds an intriguing thought: ``For some reason, there are days when you can actually perform better. It's just sort of a twilight zone. Maybe one day he'll be more in the zone than he ever has been before.''

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Photo: Experts say athletes like Michael Johnson will have a difficult time felling marks in the future.

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