One of the big questions in the buildup to Nike鈥檚 Breaking2 marathon last year was the pacing strategy. To run a two-hour marathon, should you plan to run at聽exactly two-hour pace for the entire race? Should you start a little quicker to bank some time against the threat of late-race slowdown (a fast-slow approach known as 鈥減ositive splits鈥)? Or should you hold back at the beginning to feel good for as long as possible, then use the excitement of the approaching finish to accelerate (a slow-fast approach known as 鈥渘egative splits鈥)?
In theory, you can construct pretty reasonable physiological arguments for all three approaches. Several months before the Breaking2 race, when I asked Nike鈥檚 scientific team about their pacing plans, they still hadn鈥檛 decided. Part of the challenge, they explained, is that pacing isn鈥檛 just about physiology. They needed to ensure that the three athletes they鈥檇 selected were fully comfortable and confident about whatever strategy they selected鈥攁nd at that point, the athletes were evenly split. One wanted positive pacing, another wanted negative pacing, and the third wanted even pacing.
In other words, the 鈥渞ight鈥 way to pace a marathon is complicated. One way to gain insights into what works best is to get outside the laboratory and study how the fastest marathons in history have been run. That鈥檚 what researchers in Spain, led by senior author Jordan Santos-Concejero of the University of the Basque Country, have done in 聽published in the European Journal of Sport Science.
Drawing on data collected by the Association of Road Running Statisticians, Santos-Concejero and his colleagues analyzed the pacing patterns of the most recent 15 men鈥檚 world records in the marathon, dating back to Derek Clayton鈥檚 2:09:36 in Fukuoka in 1967. They divided the race into eight 5K sections, plus a final 2.195K finishing section. Overall, the athletes tended to run the second half of the race slightly (pretty much negligibly) faster than the first half.
Here鈥檚 what the first-half and second-half speeds look like, as a percentage of overall race speed:
On the surface, this looks like a pretty good endorsement of the even-split school of pacing. But there鈥檚 a catch. When the researchers split the records into two groups, the records prior to 1988 showed a distinctively different pacing pattern compared to the records since then.
Here鈥檚 what the splits from the two groups look like over the nine sections of the race (eight 5K sections plus 2.195K):
The older 鈥渃lassic鈥 records are characterized by a fast start, a progressive slowdown after about 25K, then a last gasp of reacceleration in the final 2.195K (though even that finishing kick is slower than their overall average race speed). The newer 鈥渃ontemporaneous鈥 records do exactly the opposite, starting more slowly than the eventual average pace and accelerating after 25K.
So, what鈥檚 going on here? The authors point out that the break point between the two eras happens to coincide with Ethiopian runner Belayneh Dinsamo鈥檚 1988 record. Of the older records, three were set by Australians, one by a Welshman, and one by a Portuguese runner. Of the newer records, the tally is four by Kenyans, three by Ethiopians, two by a Moroccan-born runner, and one by a Brazilian runner.
Do East African runners pace themselves differently? That鈥檚 a fraught question, but the authors point out previous research (some by Santos-Concejero) suggesting that Kenyan elite runners are better able to during exhaustive exercise compared to runners of European origin. Perhaps, they speculate, there鈥檚 some link between brain oxygenation and the ability to accelerate during the second half of a marathon. Interestingly, Ethiopian runner Abebe Bikila, who set a pair of marathon world records in the early 1960s (prior to the period analyzed in this study), paced himself more like the 鈥渘ew鈥 group of record setters.
The other big question is whether the shift to negative splits is the best way of running a fast marathon. In another subanalysis, the authors calculate the 鈥渃oefficient of variation鈥 of the nine subsegments of each race, which is a measure of how even or uneven the splits were. Plotting that number over the years, there appears to be a slight trend toward smaller variations, meaning that runners now tend to keep their pace within a narrower band for the entire race. The best example of this is the current record, Dennis Kimetto鈥檚 2:02:57, which was noticeably more even than previous records.
With this in mind, the authors suggest that 鈥渁 pacing strategy characterized by very little speed changes across the whole race may be the way to go in the future.鈥 To be honest, I think the evidence for this statement is weak (the coefficient of variation data isn鈥檛 very convincing), but I鈥檓 inclined to suspect that it鈥檚 correct, thanks to Occam鈥檚 razor, if nothing else. That, in the end, is what Nike鈥檚 Breaking2 team opted for, instructing its pacing team to run at precisely two-hour pace for as long as possible.
In the real world, of course, the challenge with perfectly even pacing is that you have to know exactly how fast you plan to run before you even start. It requires hindsight, and perhaps some circular logic, to conclude after the fact that the best way to run a given time is to have started out at exactly that pace. If we knew exactly what our capabilities were before every race, then trying to run that pace as evenly as possible would be a no-brainer.
But when you add the uncertainties inherent in real life, with time flowing in the forward direction, you still have to decide whether you鈥檙e going to err on the side of caution or ambition in your early pacing. And I鈥檓 not sure physiology will ever provide a definitive answer to that, because the 鈥渞ight鈥 approach depends on your goals and how you weight them. Is it 3:10 or bust for you? Then you should start out at a 3:10 pace. But if 3:15 or 3:20 are still meaningful secondary goals, then perhaps starting at a 3:13 pace maximizes your overall chance of a positive outcome even if it makes it slightly less likely that you鈥檒l hit 3:10.
I do think Santos-Concejero and his colleagues are probably correct that for future elite runners to keep whittling away at the world record, they鈥檒l have to set out at world record pace right from the start and maintain as even a pace as possible. The consequence, for those runners good enough to dream of records, will be lots of spectacular flameouts鈥攚hich can be fun to watch but are less fun to participate in. For the rest of us, aiming for a slight negative split still sounds like a pretty good plan.
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