Is it best to start slow in a marathon?

Posted by Dave on October 4, 2012 | 1 Comment


One of the toughest things about running a marathon is the fact that if you’re running it correctly, the first half seems almost ludicrously easy. Most runners I’ve talked to — and my own experience bears this out — say that if they feel like they are exerting themselves much at all during the first half, they inevitably crash and burn at the end. A friend of mine, the always-entertaining Allen Strickland, had this experience just this past weekend. He started a bit too fast, and although the first 20 miles felt pretty easy for him, he struggled at the finish and just missed an opportunity to qualify for the Boston Marathon.

Now, it’s probably impossible to say whether the fast start caused Allen to run slower than he wanted to at the end; there are too many other factors at play. But a new study by Andrew Renfree and Alan St. Clair Gibson seems to suggest that starting not just at your target pace per mile, but actually slower than target pace, might be the best strategy.

Renfree and St. Clair Gibson analyzed the pacing strategies of the participants in the 2009 Women’s World Marathon Championship by dividing the finishers into four groups: the top 25%, the next 25%, and so on. They compared the average speed of each group of runners to their speed when running personal-best times (PB). They found that the fastest group did better relative to their PB than the second-fastest group, and so on down the line to the slow group:

Only the slowest group, Group 4, was significantly different from the others, but the faster groups were all faster relative to PB than the slower groups. Arguably this means that the faster groups paced themselves better than the slower groups: After all, they came closer to their PRs. So what was the difference in pacing between the groups?

While slower groups tended to run close to their PB pace at the start of the race, the fastest groups actually ran slower than their PB pace for the first 10K of the race. At the end of the race, the fastest group was running closer to PB pace than any of the other groups, and doing significantly better relative to PB than groups 3 and 4.

Clearly the winner of the race had a great strategy for winning: The proof is in the pudding, and China’s Xue Bai won the race. But did she run as fast as she could? No, she didn’t set a PB. For most runners, a performance that approaches but doesn’t beat a PB isn’t great. If you’re a 3:25 marathoner and you run 99% of your PB speed, that’s a 3:27. In my friend Allen’s case, a 3:25 would have qualified him for the Boston Marathon, but his 3:27 fell short.

So while it might be a good strategy for one of the top runners in the world trying to win a championship, if you’re a recreational runner, running slower than your PB for the first 10K may not be the best way to set a new PB.

What is clear from Renfree and St. Clair Gibson’s study is that it’s probably a very bad idea to exceed your PB pace early in the race. The bottom groups ran faster than PB pace at the start of the race and paid the price at the end. Group 4’s overall average speed was just 92.4 percent of their PB speed: That’s the equivalent of 15 minutes added to a 3:25 marathoner’s pace.

What this study does not tell us is whether you should actually go slower than your PB pace at the start if you’re trying to set a PB. There’s no question that’s a better strategy than going too fast at the start, but my hunch is that the best strategy is simply to run a consistent pace for the entire race.

Note: This write-up is based on a preprint of the study, which is not slated to be published until next May.

Renfree A. & St Clair Gibson A. (2012). Influence of Different Performance Levels on Pacing Strategy during the Female World Championship Marathon Race., International journal of sports physiology and performance, PMID:


One Response to “Is it best to start slow in a marathon?”

  1. DanB
    October 8th, 2012 @ 6:39 am

    Glad you’re back