Friday, October 9, 2015

Cloudsplitter 100 Mile Race Report (2015)


Grindstone Cloudsplitter (2015) Race Report

The tweet went out less than 24 hours before we were scheduled to depart. With hurricane Joaquin off the coast and torrential rains moving in, the forest service had revoked all permits and Grindstone, my focus race for the fall, had been cancelled. An hour later, before the shock had a chance to set in, my friends had already scrambled to find alternative plans. Cloudsplitter was on the same weekend and appeared to have openings. Was I interested? Knowing nothing about the race, I looked it up. A hundred miles along a ridge on the Virginia-Kentucky border, with 25,900 feet of elevation gain (2700 ft more than Grindstone) and only one road crossing. It looked interesting. I was in.
            Lee and I (Mark and Gabe, who had also planned to run Grindstone, couldn’t make it) headed south from Cleveland on Friday morning, arriving in the evening. After a decent night’s sleep we arrived at the start in Elkhorn City, Kentucky, with a light rain falling and temperature around 50 F. As it turned out, the rain didn’t stop all day. It was sometimes heavy, sometimes light, but went on without pause until after dark. I wore a light short-sleeved shirt and carried an ultralight windbreaker in my waist pack, anticipating somewhat lower temperatures on the ridge. But the temperature stayed fairly steady through the day and night, mid-40s to lower 50s. I’m comfortable at these temperatures, even in the rain, and never did pull out the jacket.
            The course starts off with an ascent to the ridgeline, in what appears on the elevation profile to be the major climb of the race. But it’s a gentle ascent. Most of the elevation gain actually comes along the ridgeline, with a succession of short, steep ascents and descents. The cool rain was refreshing, and so far it hadn’t had much impact on the trails. I remember remarking to Lee during the initial ascent that I didn’t expect to see much mud on the course, despite the rain, knowing that the entire ridge was composed of quartz sandstone and conglomerate (I’d scoped out the geology before we left). And throughout the day, there wasn’t. One spot near an aid station (which I learned later had recently been logged) had deep, shoe-sucking mud. And there was mud in a gully that ran down the middle of long sections of trail – but the inward-sloping sides of the gully had decent traction and for the most part the sloppy stuff was avoidable. It didn’t slow us down very much on the outbound stretch.
            As we ascended to the ridge we turned onto single-track trails, and began moving through rhododendron thickets and tall trees. Occasionally we passed over bare rocky knobs with misty views of Kentucky and Virginia. Clouds hugged the valleys on either side of the ridge. It was beautiful. I lost my footing once or twice on slippery rocks, there were some calf-busting climbs, and we noticed that some sections of the trail were not very well marked. But overall the outbound traverse of the ridge was smooth sailing. We came into the Pound Gap aid station, at ~30 miles, in 8th and 9th place.
            From Pound Gap there are two iterations of a ~20 mile out-and-back stretch south along the ridge before heading back to the start in Elkhorn City. On the first outbound stretch we caught and passed a couple of runners, and at the far end of the first lap, just before turning to the aid station, Lee and I encountered two hikers carrying digging tools of some sort. One of them spoke in a pleading tone, “Can y’all help us, please?” Not breaking stride, Lee responded. “What do you need help with?” “Can y’all tell us how to get to Kentucky?” (I'd thought we were already in Kentucky…) “We’re not from here, follow us to the aid station and you can ask some locals.” We never did find out what these two wanderers were doing out there, miles from the nearest road. Lee thought they might be digging ginseng.
            We had to turn on our headlamps just before arriving back at Pound Gap, at the halfway point of the race. We were on pace for a finish of ~22:40, and in terms of effort this pace felt more or less sustainable. But with all of the foot traffic, the trails were beginning to become slicker, and muddier. And the night mist scattered the light from our headlamps, restricting visibility to a cone that extended not very far beyond our feet. It was clear we would not be able to be as aggressive on the downhills as we had been during daylight hours. Still, I felt good, and at this point a sub-24 hr finish seemed possible - even likely.
            Somewhere in the middle of the second outbound loop from Pound Gap Lee and I separated. I was a little reckless on the downhills, and she was holding back a bit to protect a sore heel. I passed a couple more runners, putting in a brief surge to gap one runner who was following me on the
My Cloudsplitter "tattoo"
downhills. Not long after, still pushing the pace a bit on a steep, rocky section, my foot clipped a rock and I took a pretty hard spill. Getting back up and retrieving a bottle that had skittered down the trail, I looked down. My left forearm had a bloody scrape, and my shins, which had borne the brunt of the impact, were on fire. But all parts seemed to be working, and I carried on.
            I returned to Pound Gap for the final time still on ~23-hour pace and feeling good. At this point I was in 3rd or 4th place overall. I power-hiked up a dirt road to the top of the ridge and was then back on single-track. The rain had stopped and the sky was beginning to clear. I caught an occasional glimpse of stars, and of the moon. But the trail conditions had deteriorated badly. Many sections were slick, soupy mud. I slid down one smooth hill almost like a skier. Fun! The uphills, on the other hand, were less fun. It was becoming clear that the final 30 miles might be quite a bit slower than the first 70 had been.
            A couple of miles after passing through The Doubles aid station, I caught a glimpse of a large animal as it crossed the trail ahead and crashed into the woods. Although I knew there were bears here, I thought I’d seen a flash of white. A few minutes later, another animal appeared in the trail just ahead – definitely a deer. Soon I found myself descending on a wide trail with good footing – gravel and bare rock, with no mud. The trail/road continued down, and although I didn’t particularly remember this section from the outbound leg, and hadn’t seen a trail marker in a while, I didn’t consider that I might be off course. I vaguely remembered that there were some wide sections of trail here, and that there were often substantial gaps between markings. And it felt so good to be going downhill on smooth trail with sure footing...  Down and down I went, and before long I saw a light on the right side of the trail. I must be at the aid station, slightly earlier than expected. I really was moving well!

            But, no. This was a house. Hmm, I didn’t remember any houses on this section. I looked around – more houses. This was definitely not right. I must have run halfway down the mountain! I briefly considered knocking on the door of the house with lights on, but then looked at my watch – 2 a.m. – and at one of the upstairs windows, from which a large confederate flag hung. This Yankee in a kilt had better just turn around and hike back up the trail.
            And so I did – climbing steadily for 25 minutes. Approaching the ridge, I noticed a bright yellow-green marker on the left and thought I must be back at the trail, but coming closer I saw that it was a gas pipeline marker. Maybe that is what threw me off course to begin with. A few minutes later, on the ridge, I reached a clearing with a gas pipeline coming up out of the ground, but saw no course markers, and wasn’t sure where to go. Eventually I was able to make out a trail to the right, and following this for a short distance came to a cross-trail with course markings. Off I went, until I saw a headlamp approaching from the other direction. I was on the trail, but heading in the wrong direction. Grrr. I turned around - not happy to have lost 40-45 minutes and gained a couple of miles due to my own negligence, but feeling good physically and not too dispirited. I felt certain that Lee was now ahead of me and pressed ahead to try to catch up and have company again for the first time in hours.
            I was back on muddy trails now, which had gone from bad to evil. The downslopes were steep, canted, and sometimes rocky. I was slipping all over the place, and fell more times than I can count. Twice my fleet slid out from under me and I slammed flat on my back, the impact knocking my headlamp off into the mud. None of the falls hurt, but they were frustrating - and I was becoming a real mess. My gloves, my bottles – everything was caked with mud. 
And the uphills. The uphills were even worse. Steep grades – 25% and up in places – thick with mud. I panted up them, losing almost as many inches as I gained. At the crest I had to walk to catch my breath before sliding off on another harrowing descent. Even the trees had mud on them, in the shape of handprints. Progress had become painfully slow. But still, I was catching people – losing time, but regaining places I’d lost going off course. By the time I reached my drop bag at Birch Knob, 15 miles from the finish, I’d passed three 100-mile runners. But still no sign of Lee – and when I asked at the aid station I was told she hadn’t yet come through. 
I remember only a few things about the last 15 miles. The Turnip Patch Gap aid station, 12 miles from the finish, was out of almost everything – no water, no drinks of any kind, no gels. This wasn’t an issue for me because it was cool and I wasn’t relying on aid stations much at this point in the race. On a warm day, though, it could be a problem. Many of the aid stations on the course appear to be accessible only by foot or on horseback. Under these circumstances I thought the race director and local volunteers did an admirable job putting on the race. For those running it in the future, it’s a good idea to keep in mind that you can’t necessarily expect the more remote aid stations to have everything you need. Plan accordingly.
Arriving at the Goldfish Pond aid station (somewhat appropriately named, as it occupied a depression with foot-deep, orange-yellow mud) I asked how far it was to the finish. Eight miles. This was a disappointment. Given the time, I’d convinced myself that I must have missed an aid station, and that I was only 5 miles from the finish. I drank a cup of ginger ale and carried on.
The rising sun revealed beautiful views of the river valleys on either side of the ridge, which had been covered by clouds the previous morning. I reached the Elkhorn City Overlook aid station, 5.3 miles from the finish, at 8:30. From here, it was mostly a gentle downhill. The trails were sandy, and almost mud-free. I told myself I would run all of the downhills the rest of the way, and as many of the uphills as I could. My energy was good, my quads were sore but not shot, and I ran this last stretch in under an hour, arriving at the finish line with a time of 25:26:36, 4th overall and 3rd place male. Lee arrived a couple of hours later, 2nd place female. She had dozed on the side of the trail in the middle of the night, which explained why she hadn’t passed me when I’d gone off course.
Some final thoughts on the course. Overall, it is comparable in difficulty to Massanutten, which similarly runs along a ridge. Whereas Cloudsplitter is built on a gently folded sandstone unit in the hanging wall of the westernmost thrust of the Appalachians, Massanutten is built on tightly folded quartzite from a considerably deeper part of the former mountain belt’s core. The Massanutten ridgeline is more technical - rockier and off-camber - while Cloudsplitter has more ups and downs. Massanutten (in May) is likely to be considerably warmer than Cloudsplitter (in early October); certainly that was the case this year. I think if Cloudsplitter had been dry (and I had managed to stay on course…) I could have run it a little faster than I ran Massanutten in the heat. All that mud cost me close to an hour, I’d guess, over the last 30 miles. 
I expect my next big race – the HURT 100 in Hawaii this January – to combine the most challenging elements of Massanutten and Cloudsplitter. Elevation gain similar to Cloudsplitter, heat/humidity and technicality similar to Massanutten. Time to start training…

Saturday, June 6, 2015

Pacing an Ultra


When I started running ultramarathons not so long ago I was surprised at how difficult it was to find practical information on choosing an appropriate pace. For races from the mile to the marathon, it is well established how performances compare across distances, and it is easy to find tables and online calculators that help you choose an appropriate pace for a marathon, say, based on your 5k time. But if you’re running a 100k, 100-miler or 24-hr race for the first time, choosing an appropriate goal pace is not so easy. Aphorisms are pretty easy to find, and many of them, like “start slow, then slow down” I’ve found to be surprisingly effective. But quantitative information on establishing a reasonable goal time (or distance) is hard to come by. The same is true for information on race pacing strategies.

So, here is an attempt to provide some quantitative guidance on how to pace yourself during an ultra. There are, of course, a number of factors other than distance that can have a large influence on your pace, particularly if it’s run on trails. Topography, trail conditions, heat/humidity, elevation and other factors can combine to slow you by up to a factor of two or more in some of the most difficult races, even if all goes well. In most races it is absolutely critical to take these factors into account. These are discussed below, but to start it’s useful to consider the baseline case of a flat road or track ultra (even those these races aren’t currently in vogue).

Setting a Goal Time

Figure 1. Race distance vs. finish time, mile to marathon.

    A widely used algorithm for predicting race times for distances between the mile and the marathon is based on Jack Daniels’ VDOT calculator, where VDOT values essentially correspond to an individual’s level of talent and fitness. Figure 1 shows calculated finish times across a range of distances for a few different VDOT values, along with world record times for men and women. Note that each axis on this figure is plotted with a logarithmic scale, on which an equal spacing between ticks indicates a doubling of the units. Plotting the data in this way is useful because the points form nice straight lines. The important take-away from Fig. 1 is that – woman or man, world-beater or back-of-the-packer – the average pace falls off at about the same rate as the distance increases. Of course there is individual variation – some people are better at marathons, others at the mile – but in general it’s a good rule of thumb that your average race pace will fall off by about 5% for every doubling of the distance. This is the basis for calculators that allow you to set a reasonable goal for your first marathon, based on your race times at shorter distances.

Figure 2. Running world records (women - blue; men - black)
So, can you simply extrapolate from Fig. 1, and assume that your pace will continue to fall off at the same rate beyond the marathon? Sadly, no. As shown in Fig. 2 to the right, an extrapolation of the world record lines for distances of 1500 m to a marathon significantly underestimates finish times at ultra distances. The longer the race, the greater the mismatch. (I know it doesn’t look like a huge misfit on this plot – but it really is!) Why the mismatch? One difference is that, generally speaking, the shorter distance races are competed at a higher level than ultras – there are simply more athletes competing at these distances, and more of the top athletes are able to devote full time to their running careers than at ultra distances. I’m sure this plays some role, but it can’t plausibly explain the mismatch. At 100 miles, the extrapolation underpredicts the actual world records by 3-4 hours – a woman would need to average 5:46/mi over 100 miles, and a man 5:11/mi! I’m quite confident this is not humanly possible, regardless of the training regime (or doping regime, for that matter – not even Lance Armstrong levels of PEDs can buy that kind of speed in a 100-miler!). Sure, if there were more money and more competition in ultras, the records would come down a bit, and the record time vs. race distance trends would smooth out. But I don’t think the changes are likely to be huge – and they certainly won’t be enough to bring the ultra records onto the middle-to-long distance world record curve.

         
Figure 3. World record pace vs. distance (blue - women; black - men)
  
To understand the origin of the mismatch, it’s useful to look at the data in a slightly different way  – in terms of the average pace for different distances (Fig. 3). This plot shows that ultras are in a different regime than middle-distance to long-distance races – just as middle- to long-distance races are in a different regime than sprints. In contrast to the relatively small change in pace between the mile and the marathon – slowing by 5% per doubling in distance – for ultramarathons the pace slows about 16.5% for every doubling in race distance.

Why do these different running regimes exist? I have no expertise in exercise physiology, and I suspect many factors are involved, but one clear difference among the regimes is the dominant metabolic process. Sprints are anaerobic. As the race distance increases there is a gradual transition to aerobic metabolism. For middle- and long-distance events, glycogen stored in the muscles is the predominant source of aerobic fuel, but stored glycogen alone can only fuel a race of approximately the marathon distance. Beyond the marathon, the body must rely increasingly on its fat stores as a fuel source, and on carbohydrates, fat and protein that are consumed during the race. These are metabolized slowly compared to muscle glycogen –if the fuel doesn’t burn as fast, the machine doesn’t run as fast.

So, how do you choose an appropriate goal time for an ultra race distance you’ve never run? It’s probably a reasonable assumption that your own (potential) performance varies with distance in a way that is not too dissimilar from the trend of world record performances. This seems to hold fairly well for middle- to long-distances (see Fig. 1), and there’s no reason to think it doesn’t hold for ultra-distances also. As a general rule of thumb, you could anticipate that the ratio of your performance to the world record performance is relatively constant across distances. For example, let’s say you’ve run a marathon in 3.5 hours and want to try a 50-miler. Your marathon time is 71% longer than the men’s world record time, and you could anticipate that it’s about 71% longer at 50 miles as well. Although world records are not tracked officially for the 50 mile distance, the trend shown in Fig. 3 gives a men’s world-record-equivalent pace for this distance of 3.65 min/km, which corresponds to a time of 4:52. So, you might consider a goal of around 8:20 for the 50-miler – IF it’s on a course similar to your marathon.

What About Trail Ultras?

Of course, it’s rather unlikely that the 50-miler is on flat terrain with good footing. Unlike marathons, most ultras these days (in contrast to 2-3 decades ago) are run on trails, many of them on technical trails with serious elevation gain (and loss). If your 50-miler is on this sort of course, it would be a major mistake to stick with your 8:20 plan – it’s going to take you a lot longer. But how much longer? Unfortunately, there is no simple way to account for all of the variables that come into play in a trail race. Your best bet is to rely on the performance of others who have run your target race, whose abilities you can infer from their performances in other races you are familiar with, or have run yourself.

Based on such inter-race comparisons, the folks at realendurance.com have calculated the relative finish times for a number of North American ultras, focusing primarily on 100 mile races. I am not sure exactly what their methods are, but in essence their calculations are based on a dataset for individuals who have run multiple ultras in the same year. The relative finish times for individuals in these races are averaged in some way, and normalized to the finish times for the Western States 100. The table on their site provides a useful baseline to estimate your time in a race you’ve never run, provided you’ve run at least one of the races on the list. However, if you haven’t run any of the races on the list, it’s necessary to have some other point of comparison.

Below (Table 1) I’ve made an attempt to re-calibrate the realendurance.com list of hundred-mile races to the road and track world record curve. My assumption is that the course records for the Western States 100 (14:46:44 for men, 16:47:19 for women) represent performances that are comparable to the world records for 100 miles on track. This seems reasonable, given the level of competition at WS100. The WS100 course record times are 28.8% and 21.7% longer than the corresponding track world record times for men and women, respectively, suggesting that the WS100 course is ~22-29% more difficult than a track. The higher value (based on the men’s records) seems somewhat more reasonable. On one end of the spectrum, it gives track-world-record equivalent times that are comparable to the actual track world record, for races that are run on flat non-technical courses. On the other end, it gives a track-world-record equivalent time for the Hard Rock 100 of 23:30, which is close to but actually a bit slower than the course record of 22:41 set by Kilian Jornet in 2014. This suggests that Jornet’s performance at HR100 may actually be superior to the track world record, or the WS100 world record held by Timothy Olson (which seems plausible enough). Similarly, on the women’s side, Ellie Greenwood’s course record at WS100 appears to be superior to Ann Trason’s earlier track 100 world record, since calibration to Greenwood’s WS100 record yields track-world-record equivalent times for the flatter races in the realendurance.com database that are ~9% faster than the actual world record.

Table 1. Relative difficulty of various North American 100-mile events, with estimated finish times that are equivalent performances to the track 100 mi world records. Based on inter-race comparisons by realendurance.com
Event
Time factor relative to WS
Time factor relative to track 100 mi WR (M)
Estd. time (hr) equivalent to track 100 mi WR (M)
Time factor relative to track 100  mi WR (F)
Estd. time (hr) equivalent to track 100 mi WR (F)
Hard Rock
1.59
2.05
23.48
1.94
26.69
HURT
1.28
1.65
18.91
1.56
21.49
Susitna
1.28
1.65
18.91
1.56
21.49
Plain
1.27
1.64
18.76
1.55
21.32
Coyote Two Moon
1.21
1.56
17.87
1.47
20.31
Grand Mesa
1.20
1.55
17.72
1.46
20.15
Wasatch
1.19
1.53
17.58
1.45
19.98
Mt. Rushmore
1.15
1.48
16.99
1.40
19.31
Massanutten
1.13
1.46
16.69
1.38
18.97
Bear
1.12
1.44
16.54
1.36
18.80
Bighorn
1.12
1.44
16.54
1.36
18.80
Superior Sawtooth
1.11
1.43
16.39
1.35
18.63
Grindstone
1.11
1.43
16.39
1.35
18.63
Pine to Palm
1.10
1.42
16.25
1.34
18.47
Angeles Crest
1.09
1.40
16.10
1.33
18.30
Tahoe Rim
1.09
1.40
16.10
1.33
18.30
Moab
1.07
1.38
15.80
1.30
17.96
Grand Teton
1.07
1.38
15.80
1.30
17.96
Eagle
1.05
1.35
15.51
1.28
17.63
Ozark Trail
1.04
1.34
15.36
1.27
17.46
Cascade Crest
1.04
1.34
15.36
1.27
17.46
Leadville
1.04
1.34
15.36
1.27
17.46
Cactus Rose
1.02
1.31
15.07
1.24
17.12
McNaughton Park
1.01
1.30
14.92
1.23
16.96
Western States
1.00
1.29
14.77
1.22
16.79
Virgil Crest
1.00
1.29
14.77
1.22
16.79
Oil Creek
0.99
1.28
14.62
1.20
16.62
Pinhoti
0.98
1.26
14.47
1.19
16.45
PCTR Headlands
0.98
1.26
14.47
1.19
16.45
Zumbo
0.97
1.25
14.33
1.18
16.28
San Diego
0.97
1.25
14.33
1.18
16.28
Pueblo Nuevo
0.96
1.24
14.18
1.17
16.12
Rio del Lago
0.94
1.21
13.88
1.14
15.78
Mohican
0.92
1.18
13.59
1.12
15.45
Haliburton Forest
0.92
1.18
13.59
1.12
15.45
Ancient Oaks
0.91
1.17
13.44
1.11
15.28
Javelina Jundred
0.91
1.17
13.44
1.11
15.28
Burning River
0.91
1.17
13.44
1.11
15.28
Old Dominion
0.91
1.17
13.44
1.11
15.28
Pony Express
0.90
1.16
13.29
1.10
15.11
Arkansas Traveller
0.89
1.15
13.15
1.08
14.94
Kettle Moraine
0.89
1.15
13.15
1.08
14.94
Sulphur Springs
0.89
1.15
13.15
1.08
14.94
Vermont
0.87
1.12
12.85
1.06
14.61
Squamish Stormy
0.87
1.12
12.85
1.06
14.61
Hundred in the Hood
0.87
1.12
12.85
1.06
14.61
Beast of Burden Winter
0.87
1.12
12.85
1.06
14.61
Run Woodstock
0.87
1.12
12.85
1.06
14.61
Mother Road
0.84
1.08
12.41
1.02
14.10
Rocky Raccoon
0.83
1.07
12.26
1.01
13.93
Lean Horse
0.83
1.07
12.26
1.01
13.93
Keys
0.82
1.06
12.11
1.00
13.77
Heartland
0.82
1.06
12.11
1.00
13.77
Umstead
0.82
1.06
12.11
1.00
13.77
Iron Horse
0.82
1.06
12.11
1.00
13.77
Boulder
0.82
1.06
12.11
1.00
13.77
Old Dominion Memorial Day
0.82
1.06
12.11
1.00
13.77
Ontario Northland
0.75
0.97
11.08
0.91
12.59
Dan Rossi Memorial
0.75
0.97
11.08
0.91
12.59
Olander Park
0.75
0.97
11.08
0.91
12.59


Pacing the Race

            Once you have identified a target race, and have set a realistic goal time (or distance, for a timed race), what strategy gives you the best chance to reach your goal? Clearly you need to put in the training, and there is a lot you may need to figure out about how to deal with various issues that appear during the race, especially if it’s further than you’ve run before. To maximize your chances, you also need to have an appropriate pacing plan. In my experience, one of the most common mistakes – in races of all distances, but particularly in longer ultras – is to go out too fast. In a hundred-miler or 24 hour race, the pace you should start at may well be significantly slower than the easiest pace you’ve run in training. It’s all too easy to go out too hard, costing yourself precious time when you later have to slow down more than you should. Not only that, but a too-fast start could well prevent you from finishing the race altogether. Given how easy the early pace feels, there is a tendency in many runners to “bank miles” early in the race – planning ahead for the (almost) inevitable slow-down that occurs later, when your legs are fried and your energy is waning. It’s tempting to do this, and in my observation most runners (90% or more?) follow (whether by design or not) the miles-banking strategy. It’s not a good idea, in my opinion. There is nothing inherently wrong with positive splits in an ultra, but the key to a good race is to ensure that your splits are not too positive.

            It’s a truism in endurance athletics that an even effort maximizes performance. Before looking at this in slightly more detail, I would suggest that it’s not a bad strategy to aim for even splits in an ultra, whatever the distance. If your goal time is a bit ambitious, there’s a decent chance you’ll have positive splits anyway – just less positive than they would have been otherwise. In this case, striving for an even pace is likely to produce a better result. And if you nail your goal time, or even come in under it with negative splits, it’s not the end of the world. Maybe you could have gone a little faster with a more aggressive start, but the lesson learned would at least be an enjoyable one (it’s much more fun to run negative splits than positive!).

            Let’s say you’re dialed in on a clear time/distance goal and want to optimize your chances of achieving it. What’s the best pace strategy? In a 5k, you may aim for slightly negative splits. For example, Galen Rupp’s recent US 5k record had mile splits of 4:14, 4:12 and 4:04. In the marathon, even pacing to slightly positive splits (~1-2% between the first half and second half) seems to be the best strategy. Dennis Kimetto’s world record race at Berlin in 2014 had almost perfectly even splits between the first and second half.

What about ultras? Pam Smith set the 100-mile women’s track record in 2013, running even splits (50 miles in 7:06, 100 miles in 14:11). In the same race, Zach Bitter set the US 100 mile record (and world 12-hr record) with a 4% positive split between the first and second halves. So, even to slightly positive splits appear to work quite well for times up to around half a day. For longer times, the splits tend to become a bit more positive. Sabrina Little won silver with 152 miles at the IAU 24 hr world championships in 2013; her pace in the last 52 miles was 10% slower than in the first 100. I was able to find hour-by-hour splits for Yiannis Kouros’ world record (303.5 km/189.5 mi) track 24-hr race in 1997, which are shown in Fig. 4. Kouros started at a pace that was 90% of his average pace and held it steady for about 5 hrs before it gradually dropped off. His average pace in the second half of the race was 14% slower than in the first. For longer races, the splits tend to become even more positive. In Traci Falbo’s 2014 US record 48 hr track performance (and world record for indoor), her pace in the second half was 26% slower than in the first.

So, my suggestion for pacing ultras that take on the order of a day or less would be to shoot for something between even splits and a positive split of no more than 15% between the first and second half. This of course applies to races in which the first and second halves are roughly equal in difficulty, which isn’t always the case. If it's not, your level of effort may be a better guide than your pace. It can be valuable to calibrate your level of effort by doing a timed event on a loop course, or a race on flat terrain. Some races report aid station split times for all runners, which can be very valuable in judging the relative difficulty of various sections. Finally, many races, even highly technical ones, have at least some flat, smooth sections on which you can check your pace.

One final note – while your effort level should be relatively even over the course of the race, hour to hour, that doesn’t mean it needs to be absolutely even on a shorter time scale. It often makes sense to pursue a run/walk strategy.