Boston Marathon 2012 Results: Biggest Surprises from Running's Most Famous Event

Although Monday's 116th Boston Marathon ultimately went off without too much trouble, as Wesley Korir won the men's race and Sharon Cherop won the women's, it was one of the wackiest marathons in recent memory.

Heat played a major factor.

The race was run at a much slower pace than usual and the runners were clearly being bogged down. This caused a large number of registered runners to decline to participate, and it also ruined the chances of some of the top contenders.

Here are three of the most surprising happenings from one of the most unpredictable Boston Marathons of all time.

Record High Temperatures

The temperatures in Boston in April are normally cool and ideal for running, but that simply wasn't the case this year.

When the race began, it was a manageable 70 degrees outside, but escalated from there, rising to 85 by the time Korir crossed the finish line first—reaching a high of 89 degrees by the time the race concluded.

Such heat seemed to weigh on the runners as they had to pace themselves more than usual, but most were smart enough to know their limitations. Running a marathon in any weather is a gargantuan task, but with the temperature approaching 90 degrees, Monday's Marathon was truly a test of wills.

Defending Champion Couldn't Finish

Last year, Kenyan Geoffrey Mutai won the Boston Marathon in record time, but 2012 was a completely different story as he was unable to finish. Mutai entered Monday's race as the favorite due to his impressive victory in 2011, but the heat proved to be too much. Mutai experience severe stomach cramps and had to withdraw after 18 miles.

In a race that is being run by more than 20,000, almost anything can happen, but Mutai failing to even finish came as a major shock to most observers. It would have been interesting to see how Mutai might have finished in better conditions, but the environment is a big part of running a marathon and Mutai ultimately couldn't handle it.

4,290 Registered Runners Didn't Participate 

It isn't uncommon for some runners to get cold feet and drop out after registering to run the Boston Marathon, but that was the case for thousands on Monday.

Likely due to the intense heat, 4,290 of the race's 26,716 registered participants decided not to run. Those who picked up their bibs but decided not to race will have their spot reserved for next year's race as compensation for the extreme weather.

It's one thing for professionals to run a marathon in 85-degree heat, but it's an entirely different one when it comes to inexperienced runners. While many of the marathon's participants are serious contenders, most are regular people who are out for a challenge, so it's best that many decided to refrain from running as things could have gotten scary if the heat was too much to handle.