Consider Haile Gebrselassie's world-record attempts at Berlin in 2008, where he became the first person to run under 2:04 for the marathon, and Dubai in 2009, where he faded badly in the last 10k. In Dubai, Gebrselassie was a mere 23 seconds faster at halfway than his world-record pace in Berlin the year before – that’s 1.6 seconds PER MILE difference; however, even this small shift in pace resulted in a crash that left him running 90 seconds slower than Berlin over the final 10k.
The punchline: Even the smallest of incremental efforts early on can magnify the negative effects in the latter stages of the race. In the case of Gebrselassie, running 23 seconds faster the first half led to running 90 seconds slower the second half – resulting in an overall slower run by 67 seconds between his Berlin and Dubai marathons.
OPTIMAL PACE STRATEGIES FOR YOUR RACE DISTANCE
5K and 10K
A recent study in the Journal of Strength and Conditioning Research demonstrated that in order to optimize 5K performance, runners should start the first mile of a 5K race at paces 3 to 6 percent faster than their goal race pace. When test subjects ran 3 to 6 percent faster the first mile, settled in to goal pace for the middle miles, and kicked the last 800m, their finishing times were, on average, 29 seconds faster than those runners who started slower than, or at, goal race pace.
The researchers also caution against starting out too quickly. Running the first mile more than 6% faster than goal race pace negatively impacts performance considerably, in some cases causing runners to end up jogging across the finish line.
Other studies show ideal pacing for the first kilometer (rather than first mile) is 3 to 4 percent faster than goal race pace, and a strong finishing kilometer to cross the line.
10-Mile and Half Marathon
From an energy-use perspective, we know that races of this distance should be run slightly below to at your lactate threshold pace, depending on how fast a runner you are. Running faster than your lactate threshold creates a situation where the aerobic system is unable to keep up with removing waste products that cause muscle fatigue that are being generated by anaerobic energy production. Consequently, it's important that runners run slightly slower than this threshold for as long as possible, particularly at the start of the race, to prevent waste products from building and causing fatigue during the early miles. Think of exceeding your lactate threshold as lighting a fuse. Once it’s lit, it burns until the TNT explodes. The faster you run, the faster the fuse burns and, consequently, the quicker the TNT explodes.
From a psychological perspective, it's also important to hold back a little at the start of a race. This is so when it’s time to let out the reins and really kick it in the final 2-3 miles, you know you can do so with confidence because you know you have not yet lit your fuse. To do so, runners must start the first mile or two of a race slightly slower (5–15 seconds/mile) than goal pace to ensure they have both the physical and psychological resources in reserve to finish strong.
World-record attempts are great examples to show how a negative-split strategy is optimal when seeking PRs in the marathon. We can also look at other elite performances on challenging courses, those that are not pancake flat. To be clear, running the first half of the marathon faster than goal pace in order to “put time in the bank” is a losing strategy. Sure, you may set a PR but you will most definitely not run the fastest race you have within yourself.
For example, let's consider the men's and women's top runners at the 2011 New York City Marathon. Mary Keitany's goal on race day was to win the race and set a course record. The course record at NYC is 2:22:31, and Keitany scorched the first 13 miles in 1:07:56. Even at 15 and 16 miles, Keitany was still more than 6 minutes faster than record pace, and she had what seemed an insurmountable 2:24 lead on the next pack of women. Over the final few miles, Keitany fought hard and ran tough, but she eventually finished third with a time of 2:23:38, more than a minute over the course record and 8 minutes slower than projected at 16 miles.
The men's race in 2011 was quite the opposite. The men raced in a tight pack of 10 runners through halfway, reaching the 13.1-mile marker in 63:17–a 4:49/mile pace and just under the old course-record pace. The pace remained "gentle" until 20 miles, when a pack of seven runners ripped off a couple of 4:30 mile splits. At mile 24, eventual winner Geoffrey Mutai broke away and crushed the previous course record by finishing in 2:05:06, averaging 4:40/mile for the last 10K and 4:47 for the race.
When it comes to how your body works, the main issue with the "put time in the bank" strategy concerns burning through available muscle glycogen. The more intensely you run, the faster you burn through the glycogen. Muscle glycogen is like gas in a car’s tank – when the tank is empty, the car can’t go anywhere. This is akin to the dreaded bonk, when your legs feel like lead and you fantasize about Big Macs or donuts.
Consequently, what makes sense for the marathon is to run your first 3 to 5 miles at slower than goal pace to conserve energy, maintain goal marathon pace through 20–22 miles, and then run your fastest over the last 4-6 miles.
DEVELOPING A SENSE OF PACE
It’s critical to learn what it feels like to run at goal pace – what sensations are you experiencing, how do your legs feel both early on and later on, what is your breath rate like, and so on. It is also critical to trust in the pacing process come race day. It is so very easy to start out too fast because you’re surrounded by the excitement and energy of other runners. It is imperative to focus on yourself, the sensations you’re feeling and to not panic. If you end up starting out too slowly the first mile, that’s OK! You’ve got plenty of race left, regardless of the distance, to speed up. Better to start 5 to 10 seconds too slowly than that many seconds too fast.
By understanding the reasons behind optimal race day pacing, you can go into your next race with greater confidence in how to pace your race and, just as importantly, why you need to pace your race that way. After all, if it works for the fastest runners in the world, it will work for you as well.