Race Time Prediction

Have you ever seen those race prediction calculators or charts?  You looked at your latest 5K time and perhaps saw what time you might be able to run for a marathon.  Did you believe the answer?  Did you actually try it, only to miss the projected time badly, leading to frustration and self doubt?  We did too and thought we would research it a little more.

What we found is that the tables or calculators use a formula based on world record times.  If the marathon world record is 9 times slower than the 5K world record, it takes your 5K time and multiplies it by 9 to get your predicted marathon time.

That sounds reasonable, doesn't it?

We think not.  First of all, the formulas used are very old.  Do you think the ratio of Roger Bannister's 3:59.6 mile in 1954 to the marathon record of about 2:20 at that time provides the latest data.  All of the formulas appear to be almost that far out of date.  They predict that anyone who can run a 13:01 5K (about 3 dozen men worldwide) can run a 2:04 marathon.  The first is a decent standard for "world class".  The latter is 1 second off of the world record.  Obviously, all 3 dozen men can't run a 2:04 marathon.  In fact, when 13 minutes was broken for 5000 meters, the marathon record was 2:07:12.  The only man who ever has run a 2:04 is Haile Gebrselassie.  He not only has run 12:39 for 5,000 meters, but also is probably the most gifted endurance athlete ever.  By that we not only mean he can outrun everyone else, but he translates the speed he has into endurance, by holding a very fast pace for a very long time.  A 2:04 marathon is 4:44 per mile for 26.2 miles!

A second issue besides the outdated ratios, is that Haile was probably running 140 miles per week when he was preparing to set the world record.  How many runners do you know that are running 140 miles per week?  Do you think the average 25 minute 5K runner can hold a pace only 45 seconds slower for 26.2 miles?  Not likely.  Us mere mortals run 40 miles per week for some, to 80 miles per week for the more elite, trying to get ready for a marathon.  Why would we be able to hold as high of a percentage of our maximum capability for an entire marathon as someone who runs almost a marathon every day?  Yet, every prediction chart or calculator we have found uses the same ratio for the 30 minute 5K runner as the super elite.  We have never seen runners actually live up to those expectations.

In response to these issues, we created the table below.  It first of all, uses the ratio of the current world records for the super elite.  We then have a factor included that backs off of the predicted values incrementally as you go up the chart to less elite times.  This back off in performance, or increase in slowdown, for the less elite was based on actual performances recorded for well conditioned athletes.  By well conditioned, we are not referring to 140 mile per week runners, but athletes using targeted, appropriate training, similar to our articles Training for the Serious Runner or  Marathon Training - Intermediate.  Note that this level of training is important to ever translate a fast 5K PR into a Boston qualifying kind of marathon time, but less than this can translate a 5K time into a comparable 10K time, assuming your long runs are long enough that the distance itself is not a challenge.

In using this chart, please note that results vary by individual.  Some of us have more speed and some more endurance.  Also, if moving up in distance a fast marathon or half marathon may require stepping your training up.  However, with that  said, each row in this table is approximately comparable in skills and capability.

The bottom row are world class times, but not (male) world records.  They use the ratio of current world records to compare times.  As you go up each row, there is a progressive slowdown over distance as you progress through the ranks of the rest of us.  For example, the top row is about 20 minutes slower than the world record ratio for the marathon (which is still very challenging).  Our data says we are pretty close, on average, if you really do the training, and the other charts are unobtainable for most runners.  For example a 25 minute 5K runner is not going to run a sub-4 marathon (like other charts predict) unless they really improve their 5K time also.

We offer this as a data-based alternative to the other demoralizing prediction charts and calculators.  It is still challenging as you move up in distance, but actually achievable without running 140 miles per week like Haile.  We greatly admire him, but we can't emulate his performance or his training.

Note: One possible exception to not being able to meet the expectations of other charts is a woman I trained with who I could beat in a 5K by 20 seconds or so, but beat me by 15 minutes in the marathon.  She was about the ultimate on the endurance side of the equation.  She never reached world class status, but did place in the top 10 at the Disney Marathon and went on to be an "elite" seeded runner when we both ran Boston.  However, she is the (extreme) exception and not the rule.

Copyright 2011 by Florida East Coast Runners and Frank Norris.  Reproduction or reprinting without written permission is illegal.

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