Leadville 100 Race Week: Setting Your Altitude Heart Rate Ceiling¶
The gun goes off at 4:00 AM Saturday. It's dark, cold, and a minute into the race your heart is beating faster than your legs think they're asking for. That is not nerves. That is 10,200 feet.
You already know that altitude does this. What you may not have yet is your personal number: the heart rate ceiling, built from your own data at this elevation, that tells you whether you're working within capacity or taking out a loan you can't repay before Winfield.
Thursday and Friday are where that number comes from. Here's the method.
You're already doing the test¶
The moment you stepped off the plane or out of the car in Leadville, your cardiovascular system started adjusting to 10,200 feet. It's been running a live test ever since, tracking how hard it has to work to move oxygen at reduced atmospheric pressure.
Every walk to the convenience store on Harrison Avenue, every climb up the stairs at your motel, every easy shuffle on the dirt road at the edge of town is generating altitude baseline data. You don't need a lab to collect it. You need a heart rate watch and two mornings.
The pre-race days are not dead time. They're your calibration window. And you're already running it whether you're treating it that way or not.
Two days, two numbers to write down¶
Two readings matter.
The first is your resting HR: taken first thing in the morning before you get out of bed, before coffee. Lie still for two minutes and read the number.
The second is your easy-effort HR: put on your watch, walk or shuffle for 15 to 20 minutes at a conversational pace (the kind where you could string together four sentences without gasping), and read your average HR for the final 10 minutes of that effort.
Both readings will be higher than your sea-level equivalent. That is expected. For the physiology behind it, the altitude racing post has it in full. At this point, you just need the numbers.
Take both readings Thursday morning and Friday morning if you arrived Wednesday or earlier. If you arrived Thursday, take both days. If you're arriving Friday, take resting HR that morning and skip the easy-effort run entirely. Running at effort the morning before a 100-miler is not worth the data.
| Arrived | What to collect |
|---|---|
| Wednesday or earlier | Resting HR + easy-effort HR both mornings; average the two easy-effort readings |
| Thursday | Resting HR + easy-effort HR both mornings; average the two easy-effort readings |
| Friday morning | Resting HR Friday morning + easy-effort HR Friday morning |
| Friday afternoon or evening | Resting HR only; default to the conservative end of every ceiling range in the table below |
The number you're pulling from this is your altitude BL: your easy-effort HR at Leadville elevation. If you only have resting HR and no easy-effort reading, add 25 BPM as a rough estimate. It's imprecise, but workable.
One note on the resting HR number: if it's more than 15 BPM above your sea-level resting HR in the absence of illness, that can be an early indicator of altitude mountain sickness rather than normal adjustment. If you're seeing that, talk to the race medical staff before Saturday.
Building your segment ceilings from your own baseline¶
Once you have your altitude BL, use it to set a ceiling for each major course segment. The ceiling is not a target. It is the line above which you should slow immediately, regardless of how early in the race it is and regardless of what pace that implies.
All values are expressed relative to your altitude BL. If your BL is 145 BPM, "BL + 8" means 153 BPM.
| Segment | Miles | Elevation | What to expect | HR ceiling |
|---|---|---|---|---|
| Start to Mayqueen | 0 to 13.5 | ~10,100 ft | Cold air and adrenaline both spike HR in mile 1; the road is mostly flat but crowd pace is not yours | BL + 5; it will feel slow. That's correct. |
| Mayqueen to Fish Hatchery | 13.5 to 23.5 | 10,000 to 9,820 ft | Slight net descent, tempting to press | BL + 8; don't treat the descent as stored energy |
| Fish Hatchery to Twin Lakes outbound | 23.5 to 39.5 | 9,820 to 9,200 ft | Lowest elevation on course; the one stretch where HR can run a little warmer | BL + 10 |
| Twin Lakes to Hope Pass summit | 39.5 to 45 | 9,200 to 12,600 ft | 3,400 feet of climb in 5.5 miles; HR climbs whether you run or hike | BL + 15 to 18; when you hit ceiling, power hike until HR drops |
| Hope Pass summit to Winfield | 45 to 49.8 | 12,600 to 10,200 ft | HR should fall on the descent; watch for HR that won't drop | If HR stays above BL + 10 for more than 5 minutes of descent, that's a signal |
| Winfield to Hope Pass summit (inbound) | 49.8 to 60 | 10,200 to 12,600 ft | Second climb; 50 miles on your legs and the same 12,600 feet ahead | BL + 12; tighter than outbound because fatigue compounds oxygen demand |
| Hope Pass summit to Twin Lakes inbound | 60 to 60.5 | 12,600 to 9,200 ft | Fast descent; HR drops but quads absorb the impact | Don't chase pace on this descent |
| Twin Lakes inbound to finish | 60.5 to 100 | 9,200 to 10,152 ft | Long final section; fatigue-driven HR creep is the defining feature of the back half | Return to BL + 5 as the target; any drift above BL + 10 is an early warning |
The outbound Hope Pass ceiling is intentionally wide (BL + 15 to 18) because the climb is unavoidable. You can't pace around 3,400 feet of gain. What you control is how quickly you acknowledge the ceiling and shift to hiking.
The inbound Hope Pass ceiling is tighter (BL + 12) for a reason. Runners who treated the first crossing as a ceiling test tend to apply the same logic to the second. Mile 60 is not mile 45. The legs that handled BL + 18 on the outbound don't have the same capacity six hours and 50 miles later.
What drift looks like vs. what it means¶
HR drift at altitude is not a failure. Your cardiovascular system is working against a lower oxygen supply and a growing fatigue load at the same time. Some drift is baked into how this race works. The question is whether the drift you're seeing is expected and self-limiting, or compounding.
Three scenarios to know before you're in them:
Scenario 1: HR spikes above ceiling on the climb to Hope Pass, then drops back below ceiling within two to three minutes of hiking at a steady pace. This is normal. Keep hiking. The ceiling is working.
Scenario 2: HR sits at or above ceiling for more than five minutes on a section that is not a major climb, like Fish Hatchery to Twin Lakes or the miles from Winfield back to the base of Hope Pass on the inbound. Slow to a walk immediately. Drift that persists on flat or gradual terrain means your system is not recovering between efforts. That deficit compounds.
Scenario 3: HR is at or above ceiling through the final 40 miles and won't respond to slowing. This is late-race territory where fatigue, fueling, and sleep debt have taken over from altitude alone. At this point, the HR data shifts from ceiling signal to speedometer: you know you're not accelerating, and you're managing movement to the finish. If you're tracking against the cutoffs, the Leadville cutoff math post has the split targets for Twin Lakes inbound and Mayqueen to cross-reference.
The 4am factor¶
The first two miles Saturday morning will feel wrong on HR for reasons that have nothing to do with your fitness or your altitude calibration. Cold air at altitude contracts blood vessels, which raises HR independent of effort. Adrenaline after six months of training and a 4:00 AM gun produces a real cardiovascular response. Predawn temperatures in Leadville in late August typically sit between 35 and 45 degrees Fahrenheit at the start.
For the first two to three miles, your HR is not yet a reliable effort signal. It will be elevated from cold and adrenaline before it settles. The ceiling table above applies from around mile 3 onward, once core temperature has normalized.
The only thing to do in miles 1 and 2 is go slower than you think you need to. Every runner who has seen both mile 2 and mile 90 of this race will say the same thing.
One check before you sleep Friday night¶
Before you go to bed Friday night, take your resting HR one more time. Lying down, two minutes, before caffeine.
If it's more than 8 to 10 BPM above where it was Thursday morning, your body is still adjusting. Use the conservative end of every ceiling range in the table. BL + 5 instead of BL + 8 on the early miles. BL + 12 instead of BL + 15 on Hope Pass outbound.
If it's tracking flat or lower than Thursday, you've adapted as much as you're going to before the gun. Run the midpoints with confidence.
That's the whole check. Two minutes, one number, one decision. Then sleep.
The HR ceilings tell you how hard to run each segment. The cutoff math tells you how fast. Both need to line up on Saturday.
If your Strava is connected to NavRun, your last seven days of resting HR data are already there. Your altitude baseline is in that data.