Even Pacing Should Sometimes Mean Uneven Splits

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This article originally appeared in the January 1989 issue of UltraRunning Magazine

By Charles Greene

The Firetrails Fifty 50-mile trail race has taken place each of the past six years; in all there have been 155 finishers, several of whom have run it more than once. The course is out-and-back, primarily on fire roads (33%) mostly exposed to the full strength of the sun, and trails (24%) mostly offering partial to full protection from the sun. The remainder is a paved bike path and two short sections of road. Most of the course (87%) coincides with the East Bay National Skyline Trail. There is about 4,000 feet of elevation gain and 3,200 feet of loss for a net gain of 800 feet outbound. The inverse holds true for the return.

For each of the six races each runner’s arrival time at each of the 13 aid stations has been recorded. I used a spreadsheet program to manipulate the data in various ways, generating reams of output, some of it quite perplexing. My ultimate purpose is to develop techniques for analyzing Western States splits so as to optimize aid-station arrival times for various projected finish times.

Because the race is out-and-back and because the return has a net elevation loss I expected most runners would run close to even splits but a comparison of the halfway and the finish times showed this to be false.

The bar graph shows the return time as a percentage of the out time for those runners finishing in each half-hour increment of finish time. There is only one runner in the first half-hour and three in the second half. Only six finishers in the event’s history have recorded negative splits, and no runner finishing over 10:30 has ever been close to a negative split. The averages accurately represent the data, although there is much more scatter in these percentages as the finish times increase.

even-pacing

Perhaps the return leg is tougher despite the 800-foot net loss. I have measured all of the poorly-measured sections of the course and compiled an accurate course profile (see the Dec., 1988, issue of Ultrarunning) using USGS maps. There is 7.2 miles of 3% or greater grade (a 5% grade requires 35% more energy than level running) going out and 7.3 miles returning. Identical. The relative proportions of short steep grade to longer more gentle appears to be about the same. (I have a hunch that large elevation gains made over short distances are more energy efficient than the same elevation gains made over relative long distances.

That is, I prefer to gain elevation walking up short steep hills rather than gaining the same elevation trying to run up an 8 or 10% grade. Someday I am going to try to confirm this.)

Some of the slowdown can be attrib

uted to going out too fast and dying. And some can be attributed to general fatigue, especially for those out there for more than 10 or 11 hours. But I think the percentage of time exposed to the hot afternoon sun accounts for a significant percentage of the slowdown.

Bob Glover in his book, The New Competitive Runner’s Handbook, suggests a 25- second-per-mile slower pace at 80° degrees over the 50°-degree pace for six- to eight- minute-per-mile 10-km runners. He further says that slower runners “are often affected even more by the heat” and “it could be worse … over a marathon.” In Galloway’s Book on Running, leff Galloway, based on personal experience and the opinion of others suggests a 20% slower pace for 80°-85° conditions.

The Firetrails Fifty starts at 6:30 a.m. with a temperature of about 50° (there was ground fog in the valleys this year for the first 7 or 8 miles) which rises to possibly 80°

or 85° on the exposed ridgetops by one or two in the afternoon. Most of the runners who finished in under 10 hours had reached the turnaround by 11 a.m. and all of the runners had reached that point before noon. If we assume that it is decidedly warm by 11 a.m. then all of those runners who took more than four and a half hours to reach the turnaround ran the return leg in significantly higher temperatures than the out leg. The faster runners, of course, spend a smaller percentage of their time running in the higher temperatures and are well on their way back by 11 a.m.

Optimal pacing is based on even effort (energy expenditure) — the effort is constant and not the pace. Even effort demands a slowdown in pace in the presence of higher temperatures (and hills and poor traction) because the body expends some of its energy to promote cooling and blood is diverted away from the running muscles to the peripheral areas of the body to facilitate cooling. Interestingly, this suggests that even splits for out-and-back races where high temperatures are encountered in the second half are a sign of poor pacing! Does the high afternoon temperature account for most of the slowdown seen at this, and many other, ultras? I think so. Any ideas?

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