A talented young group at the top of the world marathon rankings — and a speculated step up to the distance for the 2012 Olympics by 5,000 meter and 10,000 meter world record holder Kenenisa Bekele — will produce shocking results, but the 4:34 per mile pace required for a sub-two-hour marathon is too close to the half marathon world record for the next hour barrier to be in jeopardy.

With the training resources available to today’s athletes, records in several sports that were once safe are being shattered. Usain Bolt, Lance Armstrong and Michael Phelps are enigmas. Their feats are more publicized than distance running’s phenom, Samuel Wanjiru the half-marathon world record holder of Kenya, but Wanjiru’s nearly half-minute margin ahead of marathon world record holder Haile Gebrselassie’s half-marathon time, which he bested in 2007, makes the 22-year-old the most apparent threat to the two hour feat. Wanjiru could cover nearly another mile though in the 3 minutes and 59 seconds between Gebrselassie’s marathon record and the milestone.

On Sept. 28, 2008, Gebrselassie, from Ethiopia, lowered his record set on the same Berlin course a year earlier by 27 seconds and became the first to cover the 26 mile, 385 yard distance within four minutes above two hours, stopping the clock at 2:03:59.

In five years, nearly an entire minute was shaved off Kenyan Paul Tergat’s record 2:04:55 clocked in the 2003 Berlin race. Four minutes seems like a blink of an eye compared to the other two hours of continuous running, but when the average mile split of the world record is 4 minutes and 43 seconds, the discussion becomes scientific to determine whether the human body can sustain a greater effort.

Although Gebrselassie was able to take almost half a minute off his record in one year, it took 25 years to complete the last four-minute progression. Great Britain’s Steve Jones set a world record of 2:08:05 in 1984 at the Chicago Marathon.

Both Gebrselassie and Tergat set the half-marathon world record before breaking through in the marathon. Wanjiru broke Gebrselassie’s half-marathon record of 58:55 in 2007 a month after it was set with a 58:33 in the Fortis City-Pier-City Half. Wanjiru, who won the 2009 Flora London Marathon with a personal best 2:05:10 and the gold medal in the 2008 Olympic Games Marathon in Beijing, went through the first 10 kilometers in The Hague, The Netherlands in 27:27.

Mount Desert Island Marathon Race Director Gary Allen ­— a member of the trio bounding up the hills of Acadia National Park’s carriage roads — pointed out that the 2009 Beach to Beacon 10k — an elite event held in Cape Elizabeth — was won by Kenya’s Ed Muge in 28:05. Wanjiru covered more than twice the distance at a pace of 4:28 per mile, and his arranged pacesetters could not keep up.

Wanjiru’s race proved that at the pace required of a sub-two hour marathoner, even elite pacesetters would be of minimal assistance. Unless a cooperative group of runners were able to match Wanjiru’s ability, maintaining a 4:34 mile clip for the second half of the race would be an unthinkable solo effort.

By the time Sunday’s running group finished and returned to the parking lot, another 22-year-old from Kenya, Sammy Kitwara, became the sixth person to eclipse the 59 minute barrier in the half, winning a race in Rotterdam, The Netherlands, in 58:58.

Wanjiru’s first of three career marathons was in London, so he has not been tested on the flat and fast Berlin course, which is void of 90 degree turns that slow the field down. Four of the last six progressions in the marathon world record were run in Berlin. Wanjiru’s next attempt at Gebrselassie’s mark will be at the Bank of America Chicago Marathon on Oct. 11. American Khalid Khannouchi set the world record at 2:05:42 in Chicago in 1999 when he was a Moroccan citizen, and two of the last three women’s records were set there.  Chicago’s lack of hills resembles the Berlin course.

Examining trends in the progression of the marathon record reveals the contrasting era’s of distance running. As the jogging craze of the late 1960’s through the ’70’s hit, and athletes were allowed to compete professionally as well as maintain their Olympic eligibility, the marathon world record was lowered significantly and frequently. That phase settled down in the ’80’s, before the Africans began their dominance at distance running and began moving into uncharted territory.

The World Marathon Majors (Boston, London, Berlin, Chicago, New York) series standings show a depth of talent that history has not seen. The paying job of these runners is to utilize scientific findings in their time consuming training regimen and earn prize money at world-class events. The extent of the research is only as valuable as the human body is willing to benefit from it though, and physiological limitations will likely allow sub-three-hour marathoners to maintain the pride that they are within the same hour as the world record holder.

Last Monday, Ryan Hall and Kara Goucher ended the drought by both finishing third in the world’s oldest annual marathon.

The race highlighted a promising group of young American marathoners who are making an effort to deter the distance-running dominance from Kenya, Ethiopia and Morocco. Kenyan men have won 16 of the last 19 Boston Marathons, and Kenyan women have won seven of the last 10.

Ethiopian Deriba Merga won the men’s race this year, and Salina Kosgei of Kenya took the women’s race. The last American male to win in Boston was Greg Meyer in 1982, and the last American female winner was Lisa Larsen-Weidenbach, who took home the crown in 1985.

In 2006, the five most prestigious marathons in the world – Boston, New York City, Berlin, London and Chicago – collaborated to form a race series known as the World Marathon Majors. Similar to professional golf’s major tournaments, the prize money is increased for these events, adding incentive for runners to move up to the grueling distance.

Older runners have historically raced the 26.2-mile international marathon distance in the United States becuse they can no longer maintain the leg speed necessary to be competitive in the shorter distances on the track. Some exceptions to the age trend are 24-year-old Frank Shorter’s win at the 1972 Munich Olympics, Alberto Salazar winning the New York City Marathon in 1980 at age 20 and Cathy Schiro’s 2:34:24 in the 1984 Olympic Trials Marathon at age 16.

Lately, U.S. coaches have been assisting the transition of several young, elite 5000- and 10,000-meter runners who have had success in their own country in the events, but stand a better chance of competing with the Africans at the marathon distance based on their physiology.

Since 2006, nine American men under the age of 25 have run faster than 2:20.00 in their marathon debut. Eleven women since that time have opened with times faster than 2:45.00.

Hall debuted at age 24 and trained under coach Terrence Mahon of Team Running USA. Mahon felt Hall performed better in the longer duration workouts required of marathoners. Hall’s college career at Stanford University was marred by injury, though he was a two-time All-American in cross country. He won the University of Maine’s Murray Keatinge Cross Country Invitational in his collegiate debut.

Hall made a statement to the rest of the world in 2008 with a 2:06:17 in the London Marathon, giving him the fastest time ever clocked by an American-born runner. The time seeded him first among eight Africans in the elite field at Boston who had all run sub-2:08.00 marathons. Moroccan immigrant Khalid Khannouchi holds the American record of 2:05:38.

In November 2007, Hall and 26-year-old Dathan Ritzenhein took the top two spots on the U.S.A. Olympic Marathon Team. Hall went on to finish tenth in the 2008 Beijing Olympics, while Ritzenhein finished ninth.

Ritzenhein ran the London Marathon on Sunday and finished 11th at 2:10.00. The University of Colorado graduate ran his first marathon at age 23, competing in the 2006 New York City Marathon. His college track career was also shortened by injuries, and after a disappointing 11th place finish in his debut, Ritzenhein returned to New York City for the Olympic Trials and finished with a personal best of 2:11:07.

Goucher, 30, of Portland, Oregon, is coached by Alberto Salazar. She burst into the world marathon scene last November when she finished third at her marathon debut in New York City. She competed in the 10,000-meter run on the track in Beijing and finished 10th in the final. Goucher had plans of running the Boston-London double after she felt the initial pace at Boston was too slow, but Salazar reportedly talked her out of racing on Sunday.

The young American contingent has inspired some of Maine’s under-30-year-old talent to recent post-collegiate marathon success. In Boston, four of the top five finishers from Maine were age 30 or younger. Two were just 22.

Whether the youth movement is fueled by the appeal of trying something new or the potential success in an event traditionally cherished by the older generation of runners, the rest of the world should become more familiar with the young nucleus of American marathoners in the coming years.

On Monday, approximately 23,000 runners who registered before the field size limit was reached in February made their way past about one million fans lining all 26 miles, 385 yards in the 113th edition of the world’s oldest annual marathon.

At 22-years-old, it was my first trek from Hopkinton to Boylston Street, and despite a disastrous last 10 miles, the three-day experience justified for me why qualifying to run this unforgiving course and passing all of its historic landmarks is a goal for most marathoners.

I earned my qualifying time of 3 hours and 2 minutes at the Mount Desert Island Marathon in October 2008, and registered online for Boston the next day in hopes of redeeming myself from a disappointing marathon debut. I traveled down in a rental van to a hotel in Waltham, Mass., Saturday afternoon with three runners from Nova Scotia that have run the race nearly 40 times combined.

Sunday morning we awoke early to get to the pre-race expo held at the Hynes Convention Center in downtown Boston before the crowds built too much. With 23,000 runners along with their families and friends converging on the auditorium over 3 days, the set-up for number and t-shirt pick-up was remarkably efficient.

That evening we returned to the city for a pasta dinner in the City Hall parking garage. There was no shortage of food, the line moved briskly, and there was even a circus act to entertain and let us out of the wind for a few minutes as we walked through the tent.

On Monday morning, my 4:30 a.m. alarm went off, and we were out the door of the hotel headed to the Alewife subway station by 5:30. The first train of about 25 school busses idling at Boston Common was filled before 6:00. As they departed for the hour-long drive to Hopkinton, another fleet of empty ones rolled in to replace them.

Athlete’s Village in Hopkinton is an athletic field complex surrounded by hundreds of Porta-Potties, and even longer lines of runners waiting to use them. As the first of two waves of participants walked down the road nearly a mile to our assigned corral based on qualifying times, many sought out pleasant locals that didn’t mind the side of their house being temporarily turned into a urinal.

I waited in the third corral of 1000 runners as a military flyover, and a motivational address by former Boston Marathon champion Uta Pippig commenced before the 10 a.m. start. The elite women and wheelchair competitors had been given an advanced start 30 minutes earlier. The first wave was led by some of the world’s elite male marathoners, including 2008 U.S. Olympic Trials marathon winner Ryan Hall, who finished third on Monday.

I slapped the outstretched hand of a little kid in a Red Sox hat as we bounded down the steep decline of the opening miles and then focused to avoid tripping over people on all sides of me.

By the 11-mile point the crowd had dissipated enough to enjoy some personal space. The dull roar of the famous Wellesley College “Scream Tunnel” could be heard from a mile away and built to a deafening pitch as we approached. I scanned the crowd of girls on the right side of the road and quickly dashed to the barrier to give one a kiss.

My Wellesley girl’s inspiration kept me on pace for a few more miles and through the halfway point in 1 hour and 26 minutes, but I knew something wasn’t right when the same sensation in my legs that I should have started to feel with three miles to go crept in seven miles early. That’s the unpredictable part of punishing your body systems for that long though.

I lumbered over the series of four long, gradual hills leading up to the 20-mile mark that was narrowed by thoroughly intoxicated Boston College undergrads. The last and most painful rise is appropriately nicknamed “Heartbreak Hill.”

For one day a year, the giant Citgo sign behind Fenway Park’s Green Monster is appreciated more by the distance running community than baseball fans, as it marks the one-mile-to-go point.

Making the final left turn onto Boylston Street with the blue finish line banner in sight, the roaring crowd amplified by towering skyscrapers give even the most spent runner an extra push to get across the finish line.

The next few days will require frequent use of the elevator and walking down stairs backwards, but I’m already anxious to make a return run to Boston in 2010.