25 OCT 2006 General News Chicago, USA

The Marathon - pushing the limits of human performance

Berhane Adere en route to her national record 2:20:42 in Chicago (Victah Sailer)Berhane Adere en route to her national record 2:20:42 in Chicago (Victah Sailer) © Copyright

Thirty years ago the top sports medicine specialists and exercise physiologists met in New York on New York City Marathon weekend to participate in the landmark New York Academy of Sciences conference titled: The Marathon: Physiological, Medical, Epidemiological, and Psychological Studies. The proceedings of the conference were published in the New York Academy of Sciences Journal special edition, a 1090 page book with a blue cover that became a treasured resource of what was known at the time about endurance athletes. 

In Chicago last week a follow up conference was held prior to the LaSalle Bank Chicago Marathon titled the ‘World Conference on the Science and Medicine of the Marathon’.

Documenting and describing what we know

It was a mix of the old and the new and chronicled progress and changes of the last 30.  The 1976 conference was organised by Paul Milvy, an educator, environmental scientist, biophysics marathon runner.  Two marathon medical directors, Dr. Bill Roberts, medical director of the Medtronic Twin Cities Marathon, and Dr. Greg Ewert, medical director of the LaSalle Bank Chicago Marathon, organised this year's event. 

Topics ranged from the "evolution of man as a marathoner," to "the physiological limits to marathon performance," to "the central governor model of exercise performance," to medical issues such as thermal regulation and hyponatremia.  The full proceedings are scheduled to be published in a special issue of the journal Sports Medicine.  It was an intense four days of debate, discussion, and reflection on what we know and don't know about human performance in endurance sports.
 
"There really hasn't been a lot of new stuff in the past 30 years," said Dave Costill, an emeritus professor and founding director of the Human Performance Lab at Ball State University, where many of the top exercise physiologists in the US got their early training and a co-organiser of the 1976 conference.

"It's mainly been descriptive work, studies that document and describe what we know.  But we're approaching the point where we are getting the technology to examine what is going on in the body on a molecular level.  So, while we've been able to describe, thus far, the changes that a body goes through as the athlete improves, we may, with the new technology, be able to look at the genetic triggers that regulate the adaptive responses."

"Nature vs. nurture"

Costill, a collegiate swimmer, had grown up in the 1950s with runners such as Dr. Roger Bannister and Chris Brasher as idols, and became a marathon runner himself as an adult.  His passion for studying what made runners tick, therefore, was both professional and personal.  "I wanted to know why all these guys were faster than me," he said.  He used to have arguments with a top US road racer who, himself, became a renowned exercise scientist, Bob Fitts, who Costill had also coached.  Fitts was on the side of "nurture" in the "nature vs. nurture" debate of the day as to what was most important in an athlete, parents or work ethic.  Fitts believed that anybody could be a champion if he or she worked hard enough. Costill said genetics was the primary engine for champions.  Today they both agree that to rise to the top of the athletic pyramid requires the right parents, the genes that make one more adaptable than another to distance running greatness.

Twitch fibers

Harvard anthropology professor Daniel Liberman described how man had evolved to become an endurance animal two million years ago because the evolutionary adaptations during that period made man a better hunter and contributed to brain growth.  All humans, therefore, are genetically endowed to be endurance athletes because of their superior ability to dissipate heat and running economy.  The questions other physiologists are attempting to answer is whether or not there are tiny, more specific adaptations within humans that allow one person to be a superior endurance athlete.  Is it muscle fiber composition, the percentages of the various types of fast and slow twitch fibers, that differentiate the marathon champions from the also rans?  Is it structural, something in the size, power production, and/or running economy of athletes that allow them to triumph over others who train the same and/or appear to be evenly matched? 

These questions still await definitive answers, if there are any to be found.  And instead of doing muscle biopsies to examine what the tissues of champions are made of, the examination has gone down to the molecular level to see if the scientists can discover the "triggers" or adaptations champions make to training.  How they are able to transform the basic "machine" each was given into a racing machine that runs faster and/or more economically than others.

A sub-2hr marathon...in theory

Director of the Human Performance Laboratory at the University of Texas at Austin, Edward Coyle used simple physiological measurements to formulate a prediction of what the top marathoners of the day are capable of running.  Using VO2 max, a measurement of how much oxygen an athlete can utilize, Coyle used formulas postulated by fellow scientist Mike Joyner to calculate that at 80% of the top VO2 readings produced by endurance athletes today a runner is theoretically capable of running a 1:45 marathon.  These laboratory calculations do not take into account the stress 26.2 miles takes on the body, and it has not been demonstrated that an athlete can maintain 80% of VO2 max for the full marathon distance, so Coyle adjusted the calculation to include a 10% slowdown due to fatigue and still came up with a marathon time under two hours, 1:57:48 for an athlete with an 84 ml/kg VO2 max.  Coyle also showed data compiled by British exercise physiologist Max Jones on Paula Radcliffe that used similar physiological parameters to predict that Radcliffe is capable of running the marathon in 2:13, not far from her 2:15 world best, and she is still improving, raising the possibility that she could run even faster.

Identifying the physiological attributes of champions

Jones' data on Radcliffe, that stretches back to 1991, shows that she has been able to steadily increase her "running economy" over her running career at an average rate of about 1% a year.  While that doesn't sound like much, over more than a decade it amounts to a significant shift in her ability to run fast, which has been mirrored by Radcliffe's steadily improving performances.  All of this is what Costill described earlier as "descriptive" work.  It chronicles physiological changes that can be compared to performance.  The unanswered question and focus of future research is why?  Do Radcliffe and other champions have some identifiable physiological attributes or adaptations that other athletes don't?  What is happening inside her muscles?  Does her body respond the same or differently to the stress of training?  Is there something in her genes and/or physical composition that makes her a champion?

Processing oxygen

Back in the 1970s, Dr. Michael Pollack and other physiologists, collaborated to study the top US distance runners of the era, such as 1972 Olympic champion Frank Shorter and Steve Prefontaine.  The data gathered from these athletes, such as muscle biopsy samples and oxygen consumption data, provided a profile of the make up of top endurance athletes but also created almost as many questions as it answered. 

Foremost among them, perhaps, remains the issue of what is lumped into the term "running economy."  It is sort of a catch all term used to record the fact that an athlete can run at a given speed at a given cost. Some runners can run at higher speeds seemingly because they have a greater ability to process oxygen.  They have a higher VO2 max.  Others, with lower VO2 readings, can run as fast or faster, presumably because they are more "efficient."  But what makes them more efficient?  What allows them to generate as much or more power and maintain their speed for as long or longer than other athletes?  These are the mysteries that future studies may discover.  These are the questions that may be answered by research into the "triggers" of athlete's physiological adaptations to the training they endure to reach the heights of athletic excellence.

Coaching - a mix of art and science

Is there a "central governor" within every athlete that determines how he or she performs?  If so, what is it?  The brain?  The central nervous system?  Something else?  These are all questions that are searching for answers.  Are there ultimate limits to athletic performance?  Is a 1:45 marathon possible?  Will somebody run under two hours for the marathon anytime soon?  They seem to be physiologically possible, but are there elements of physiology and/or endurance performance that we still need to probe more fully to get these answers?  The answer to that question would be a resounding yes. 

As Costill once said, the sports scientists usually "discover" what coaches already have figured out from years of trial and error in training athletes.  Coaching is really a mix of art and science, said Costill, who was both a coach and a scientist during his career, and science usually lags behind art in understanding or discovering the keys to human performance.  So, while the secrets of sporting ability may be eventually explained in the laboratory, they are usually discovered during the time coaches and athletes train to improve their times, pushing the limits of human performance.

Jim Ferstle for the IAAF