Apr 11, 2019 7:00 AM

How the Boston Marathon Messes With Runners to Slow Them Down

The course is mostly downhill and has few dramatic turns, yet it ranks among the slowest marathons in the world. Here's why.

The Boston Marathon course looks like it should be fast. You start out in the distant suburb of Hopkinton—elevation 490 feet above sea level—and then cruise steadily downhill until about mile 9. The finish line has an elevation of a mere 10 feet above Boston Harbor. Fans pack the sides cheering you on. The route is pretty straight, west to east, with few 90-degree turns of the sort that slow your momentum. The road is asphalt, which is more forgiving than concrete.

So when the gun goes off Monday morning for the 123rd running of the race, everyone should feel good about hitting a personal best, right? Of course not. As every veteran marathon runner knows, Boston is slow, wicked, and tempestuous. It’s a wonderful course if you want to experience camaraderie, history, and emotional uplift. It’s a terrible course if you want a personal best.

The average finishing time in Boston is fairly good, but that’s just because you have to qualify for it. People run fast in other marathons so that they can get into Boston, where they will then slow down. The men’s winner in Boston last year ran 2:15, while the winner in Berlin ran 2:01. The 10th place man ran 2:27 in Boston, a time that would have gotten him 72nd in Berlin. The 10th place woman in Boston ran a time that would have gotten her 39th in Berlin.

Of course, one race on one day isn’t a good way to analyze results. The weather last spring on Marathon Monday in Boston was hellacious: driving wind and freezing rain. More than 60 percent of the elite men dropped out. So many elite women dropped out that a Spanish teacher at my Boston-area high school, who had never placed remotely as highly in a major road race before, came in fourth. In other words, 2018 was a particularly bad year to head from Hopkinton to Kenmore Square. But it’s also true that, in general, Boston is slow. And the reason comes down to at least four factors, all of which are partly endemic to the course itself.

The first and most important is temperature. Running quickly generates heat, which the body needs to dissipate. The ideal temperature for running a marathon is roughly 45 degrees Fahrenheit, though the faster you are the colder you want it . Cloud cover is probably good. In Boston, if the sun’s out and you’re not paying attention, you’ll get a sunburn on the right side of your body. Rain, which makes roads slippery and clothes heavy, can feel good but is actually bad. Humidity matters too, since the more vapor there is in the air, the harder it is for a runner to dissipate heat. Boston’s weather in the spring is famously unpredictable. In 2004, temperatures on the course reached 85 degrees. In 2007, the wind chill was in the 20s. In 2012, it went back up into the 80s and more than two thousand runners needed medical treatment for heat-related illnesses.

What’s the weather going to be on Monday? Not great. Enter the current nasty forecast for Boston—15 mph winds, 50 degrees, and 75 percent humidity—into a race calculator, and it suggests one should revise one’s goals downward by roughly two to three minutes. And that isn’t even taking into account the hills.

The second factor affecting the speed of a course is elevation, and downhill is good. But downhill isn’t unambiguously good. Runners have to fire their quadriceps muscles to keep from tipping over when a hill is too steep. The wear and tear builds up over the course of a race, particularly for runners who haven’t been training on similar terrain. And Boston has a series of famously steep uphills between miles 16 and 21, just when your glycogen stores are running out. “Downhill running requires a bit of braking and eccentric contractions that can wipe your legs out,” says Michael Joyner, a former elite marathoner and current sports scientist. “And the hills at Boston are at exactly the right place to make people suffer as a result.”

The hills don’t hurt everyone the same. I spoke with Alan Ruben, a legendary local runner who completed 15 consecutive New York City marathons in under 2:40. His theory is that Boston is actually faster than New York, and possibly as fast as London, with its historically quick course. “Boston is a hard course to execute correctly, given where the hills are. It sucks you into going too fast from the start,” he says. But he adds that if you take your time early on, the net downhill pays huge dividends. The course, in other words, is hell for rookies. But good for wily veterans who don’t blow up their quads.

The third and most interesting factor is wind. Most marathon courses finish roughly where they start, meaning that the wind will likely blow in your face as frequently as it blows at your back. The Berlin Marathon begins on one side of the Brandenburg Gate and ends on the other. On a course like that, you just want there to be as little wind as possible. On courses like New York—which is roughly south to north—you want a little tailwind, though you also know that any winds blowing from the south will hit you in the face as you come down from the Bronx toward Central Park. In general, marathon runners spend about 2 percent of their energy overcoming wind resistance on a normal day.

Boston, though, is run almost entirely west to east, which means the wind can be either entirely in your face or at your back, adding an extraordinary variability to the results. In 2007, an easterly wind pummeled runners for the entire journey. The winner finished in 2:14, and the wheelchair winners finished in 1:29 (men) and 1:53 (women). In 2011, the winds reversed. Geoffrey Mutai crossed the finish line first in the best time ever recorded there, 2:03. The wheelchair winners came in at 1:18 and 1:34.

There are ways, of course, to deal with the wind. Runners can draft behind each other, a strategy that could save approximately 1 percent of energy expenditure on an average day. (This is assuming you can draft the entire time off of someone the same size as you who doesn’t start spitting at about face height in frustration with you.) That doesn’t sound like much, but it’s the difference between running a 3:01 marathon and a 2:59. When Eliud Kipchoge set out to break the two-hour marathon, in conditions arranged meticulously by Nike, runners arranged themselves in a V shape for the entire race to cut the wind. On Wednesday, I spoke with Mebrahtom Keflezighi, who won the Boston Marathon in 2014. His advice is to tuck into a group of runners, but not too tightly. You don’t want them to bump into you or knock off your stride. And be strategic. If the wind is coming from the front, move to the back. If it’s coming from the right, move to the left.

Wind at one’s back helps, unless of course there’s too much. I spoke with Amby Burfoot, who won the Boston Marathon 51 years ago, and he told the story of how it can hurt. “In 1979, I was in New Orleans for the New Orleans Marathon, a citywide tour. The police went on strike at midnight before the marathon, and the race directors had to find a course that didn’t need security.” The race took place on the Lake Pontchartrain Causeway Bridge, beginning just as a massive storm was dying down. “The wind blew directly at our backs at 30 mph for 25 miles. Tons of people set personal records. Not me. I distinctly remember that the wind forced my body to go faster than it was conditioned for, and hence my legs cramped up.”

The fourth factor is the number of turns. Marathons are measured precisely so that the shortest line from the start to the finish is exactly an international standard based on the distance Pheidippides purportedly ran in 490 BC. But almost no one can run on that exact line. You’d have to take every turn precisely on the inside, and with every twist of the road you’d have to “run the tangents,” which means following a precisely straight line to the furthest point you can see. This is hard to do running on any road. It’s nearly impossible when jostling with 50,000 other runners, some of whom are dressed up as Elvis or Wonder Woman. A decent rough estimate is that every substantial turn in a marathon slows runners down by approximately a second. This fall, I ran both the Chicago marathon and the New York City one. According to my GPS data, my pace was better in New York, but my overall time was better in Chicago. How could that be? Because the total distance I covered in Chicago, with its simpler course, was about a tenth of a mile shorter.

So how much molasses does Boston really add to your legs? The best estimate I’ve found comes from Ken Young, an obsessive analyst of running data, known as the Nate Silver or Bill James of the sport. Over the years, he meticulously tracked runners and racers, spending roughly 50 hours a week entering numbers into spreadsheets and studying courses. According to his data, the Berlin Marathon is the second-fastest major race around, with elites going about 81 seconds faster than they would in an average race. (Paris tops the list.) Boston is one of the slowest, with elites going about 90 seconds slower. Eliud Kipchoge, who in 2018 set the world record at 2:01 in Berlin, could have put in the same effort in Boston, on a day with average weather, and finished in 2:04. He wouldn’t have even gotten the course record.

Of course no one knows what will happen on Monday. Every runner is different, and every day is different too. But if you’re doing the race, wake up on Monday morning and refresh the weather forecast. Pray for a cool, cloudy, rainless day. And, most of all, pray for winds, not too strong, blowing WSW. Also, take the advice that Keflezighi gives. “The first thing is that a marathon is going to hurt, no matter what.” And, he adds, “if it rains, it’s going to rain on everybody.”

Updated 4-11-2019, 1 pm ET: The story was updated to clarify how marathons are measured.