The science behind running

The Cooper River Bridge Run does one thing that few fitness events do: It pulls in practically all fitness enthusiasts to participate in one big 10K each year.

Marathoners and 5K addicts. Cyclists, triathletes, swimmers, group fitness exercisers and walkers. Beginners, novices and seasoned veterans. They drop their special interests for the Bridge Run, often an excuse for a fun-filled, early spring weekend of indulgences and the subject of the proverbial Monday morning "water cooler" talk.

The Bridge Run also is a local signal that, despite the tough financial times of the past two years, running for fitness not only has survived but continues to flourish.

Science has responded by studying it and offering "evidence-based" guidance to help people make good decisions and understand why running is such an efficient, natural way of maintaining a healthy body. Studies seem to pop up on a monthly basis, often turning conventional wisdom on its head, causing a flurry of reactions and sometimes creating confusion among the less-scientifically inclined masses.

Here's some of what has come out in recent months:

Marathons bad for you?

Just this month, new research by the Athens (Greece) Medical School found that marathon runners have increased stiffness of large arteries, suggesting that high-intensity exercise may actually be bad for the heart.

The study, which the researchers said was the first to examine the long-term effect of intense, protracted endurance training on the elastic properties of the large arteries, found that male marathon runners (females were not included in the study) had significantly increased stiffness of the aorta, the major artery leading from the heart, when compared with people who took part in recreational exercise.

The researchers evaluated blood pressure and artery elasticity in 49 healthy men who regularly trained to run marathons and 46 control subjects who weren't endurance athletes.

The marathoners had significantly higher systolic blood pressure (the top number in a reading) than the nonmarathoners, about 11 points higher on average when measured at the brachial artery in the upper arm. Their mean blood pressure was also about eight points higher on average than the control subjects.

The researchers said one explanation for the stiffer arteries in marathoners is that extreme exercise may place repeated and excessive stress on the artery wall, leading to its fatigue.

"Regular long-term endurance training is generally beneficial for heart health, but it seems that the cardiovascular system is like a sports car engine. If you do not use it, it will decay, but if you run it too fast for too long, you might burn it out," study lead investigator Dr. Despina Kardara of Athens Medical School, Hippokration Hospital, said in a news release.

The findings were presented earlier this month at the American College of Cardiology's annual scientific session in Atlanta.

Keeping you young

Last month, a study in Germany of active and sedentary people, both young and middle age, found that runners had less cellular damage.

From the beginning, scientists looked at the "striking" difference between active middle-age athletes compared with both sedentary young and middle-age people.

"Many of the middle-aged athletes looked much younger than sedentary control subjects of the same age," recalls Dr. Christian Werner, a resident at Saarland University Clinic.

Beneath the surface, the scientists examined white blood cells from each of their subjects and found that the cells in both the active and inactive young adults had similar-size telomeres. Telomeres are tiny caps on the end of DNA strands, and the discovery of their function won several scientists the 2009 Nobel Prize in medicine.

When cells divide and replicate these long strands of DNA, the telomere cap is snipped, a process that is believed to protect the rest of the DNA but leaves an increasingly abbreviated telomere.

Eventually, if a cell's telomeres become too short, the cell either dies or enters a kind of suspended state, says Stephen Roth, an associate professor of kinesiology at the University of Maryland who is studying exercise and telomeres.

Most researchers now accept telomere length as a reliable marker of cell age. In general, the shorter the telomere, the functionally older and more tired the cell.

The younger subjects' telomeres were about the same length, whether they ran exhaustively or sat around all day. None of them had been on Earth long enough for multiple cell divisions to have snipped away at their telomeres. When the researchers measured telomeres in the middle-age subjects, however, the situation was quite different.

The sedentary older subjects had telomeres that were on average 40 percent shorter than in the sedentary young subjects, suggesting that the older subjects' cells were, like them, aging. The runners, on the other hand, had remarkably youthful telomeres, a bit shorter than those in the young runners but only by about 10 percent.

In general, telomere loss was reduced by about 75 percent in the aging runners. Or to put it more succinctly, exercise "at the molecular level has an anti-aging effect," Dr. Werner says.

One reason why is that older runners had more activity in their telomerase, a cellular enzyme thought to aid in lengthening and protecting telomeres. Exercise may be affecting telomerase activity and not telomeres directly.

Midfoot landing is best

While you won't be seeing many people tossing off their shoes to run the Bridge Run this weekend, one study this winter gave another breath of life to the barefoot running movement and underscored the importance of running form to prevent injury.

Published in the journal "Nature" in January, a Harvard University study found that those who wear heel-cushioning running shoes are more likely (75 percent) to strike with their heels and thereby cause a jarring effect that leads to injury.

The researchers found that while people run in a variety of ways, most barefoot runners tend to strike on their forefoot or midfoot, which absorbs more impact, according to study author Daniel Lieberman, a professor in Harvard University's department of human evolutionary biology.

Lieberman and colleagues studied runners from the United States and Kenya as they ran on tracks. All ran at least 20 kilometers (12.4 miles) a week, and those in Kenya were from the Rift Valley Province, whose residents are known for endurance running.

"The human foot evolved its peculiar and characteristic anatomy in response to barefoot walking and was later tweaked, most likely due to barefoot endurance running around two million years ago," says William L. Jungers, chairman of the department of anatomical sciences at Stony Brook University Medical Center.

What to do?

Lieberman suggests that you train yourself to strike the front ball of your foot first, but that doing so requires a gradual transition to avoid developing Achilles tendinitis.

Born to run faster

Genetically, some of us were born to run and others to just jog.

In an Israeli study published in February's "Physiological Genomics," researchers examined 155 track and field athletes and found that 80 percent of those who excelled in endurance events, such as marathons, had variations of the NRF2 gene, compared with 46 percent of sprinters.

An analysis of 240 nonelite athletes produced similar findings.

While the study shows an association between these gene variations and athletic endurance, it didn't establish a cause-and-effect relationship. Further research is needed to determine precisely what role the NRF2 gene plays in athletic performance.

However, previous research has shown that the NRF2 gene helps produce new mitochondria (cellular structures that produce energy) and reduces the harmful effects of oxidation and inflammation, which increases during exercise.

"These findings suggest that harboring this specific genotype might increase the probability of being an endurance athlete," one of the study authors, Nir Eynon of the Wingate Institute in Israel, said in a news release from the American Physiological Society. "So some of us are truly born to run."

Women and pollution

A study published in the March edition of the “American College of Sports Medicine” found that higher levels of particles in the air were associated with slower performance times for women, though men were not significantly affected.

The evaluation consisted of major U.S. marathons in cities such as New York, Boston and Los Angeles, where pollution tends to be highest, in seven marathons over a period of eight to 28 years. The top three male and female finishing times were compared with the course record and contrasted with air pollutant levels, taking high temperatures (detrimental to performance) into consideration.

Although the person might not be significantly affected by low-yet-still-acceptable air quality, marathoners are atypical because of their breathing patterns.

“Previous research has shown that during a race, marathon runners inhale and exhale about the same volume of air as a sedentary person would over the course of two full days,” lead researcher Dr. Linsey Marr said in a release. “Therefore, runners are exposed to much greater amounts of pollutants than under typical breathing conditions. ... Although pollution levels in these marathons rarely exceeded national standards for air quality, performance was still affected.”

Particulate matter appeared to be the only performance-altering factor in air quality, with carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide levels not affecting race times.