Leadville Trail 100 Run
Race across the sky. 100 miles between 9,200 and 12,600 feet of elevation. Hope Pass twice. 30 hour cutoff.
The Quick Answer
Leadville is cold and high, but sodium needs do not drop the way the temperature suggests. Altitude adds 1 to 2 liters of respiratory fluid loss over the race, so add 200 to 300 mL of fluid per hour at elevation and plan 5 to 10 percent more sodium than a sea-level estimate. Use aid-station broth for 750 to 1000 mg sodium at Twin Lakes and Winfield.
Course Profile
Where The Sodium Math Bends
Schematic profile · Cramping windows tend to cluster around major climbs and the descents that follow them
Climate Window
35-78°F · low humidity
Climate
mild
Humidity
low
Cutoff
30 hours
10-yr avg high
68°F
10-yr avg low
40°F
Record high / low
73° / 33°F
Years with rain
40%
Why This Race Is Hard For Sodium
The Cumulative Deficit Window
Leadville is dry, cold at altitude, and long enough that sodium deficit compounds across the second and third night. The altitude-driven hyperventilation increases respiratory water loss, often 1-2 liters extra over a full race. Sweat sodium concentration drops slightly with heat acclimation, but most Leadville athletes do not heat-acclimate (they elevation-acclimate instead), so the salty-sweater profile shows up under-recognized. The Hope Pass climbs (outbound mile 45, inbound mile 55) are the cramping windows; the third-night cold around 1-4 AM is the hyponatremia window for athletes who keep drinking but stop eating salty calories.
Key Considerations
- Altitude increases respiratory water loss beyond sweat loss; add 200-300 mL fluid per hour at elevation versus what the calculator suggests.
- Sodium needs do not drop as much as temperature suggests; cold-weather underfueling sodium is the most common Leadville crewing mistake.
- Night 2 between Twin Lakes and Outward Bound is the hyponatremia window. Switch from plain water to electrolyte drinks after Twin Lakes inbound.
- Aid station broth at Winfield and Twin Lakes is a high-leverage sodium delivery vehicle; budget 750-1000 mg sodium from broth at each major aid stop.
Finish Times
Who Finishes, And How Fast
Typical finish distribution
Finish rate ~50%
Go Deeper
See The Full Leadville Strategy Playbook
Course segments, pacing bands, and a race-day execution guide.
Plan the five systems
Free Tools, Pre-Filled For Leadville 100
Tap any tool. We pre-load your event, climate, and sweat profile. Adjust your weight and finish target and the plan generates instantly.
Sodium plan
Per-hour sodium and fluid targets for Leadville 100 conditions.
Carb fueling
Hourly carb targets and a fuel menu calibrated to your weight and the Leadville 100 duration.
Heat protocol
10-14 day adaptation plan if you're racing into a warmer climate.
Hydration audit
Weigh-in test that converts a 60-minute training session into a measured sweat rate.
Caffeine timing
Pre-race dose, mid-race top-ups, and race-week taper protocol for Leadville 100 timing.
Related Reading
Dig Into The Science
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Best Supplements for Leg Cramps in Endurance Athletes (2026)
The 5 supplements that prevent leg cramps in cyclists, runners, and triathletes: magnesium, potassium, beta-alanine, creatine, and taurine, with clinical doses and loading timelines.
Your Leadville 100 Plan,
Built From Real Data.
Pro unlocks: sodium and fluid data from Leadville sub-25 finishers and Big Buckle holders, your altitude exposure history from Strava (training rides above 7,000 ft), and an aid-station-keyed plan with broth budgets per stop and a Hope Pass climb-specific sodium dose schedule.
- Measured sweat rate from a Strava ride or weigh-in test
- Per-leg sodium schedule keyed to the course profile
- Multi-event race calendar across the season
- Post-race feedback capture so the next plan is sharper
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Common Questions
About Leadville 100
Does altitude change my sodium needs?
Indirectly yes. Altitude does not change your sweat sodium concentration, but it increases total fluid loss (respiratory plus sweat), which means more sodium leaves the body even at the same intensity. Plan 5-10% higher than your calculator output for events above 8,000 feet.
How much fluid per hour should I take at Leadville?
Most finishers fall in the 18-24 oz per hour range when moving. Increase to 24-28 oz on the Hope Pass climbs where workload is highest. Drop to 15-18 oz overnight when ambient temperature is in the 30s.
When do most Leadville cramping incidents happen?
Two windows. First, the Hope Pass descent on the outbound leg (mile 50-55) when sodium intake during the climb was insufficient. Second, miles 80-90 on the climb back over Sugarloaf Pass when cumulative sodium deficit catches up. Pre-dose 600 mg sodium at every climb base.