Altitude Acclimation for Runners: Complete Guide to Preparing for Elevation

Racing at altitude without proper preparation can torpedo your performance. Whether you're heading to Boulder for a race or training in the mountains, understanding acclimation is crucial for success.

What Happens When You Go to Altitude

When you first arrive at altitude, your body immediately starts compensating for reduced oxygen:

Acute Response (Minutes to Hours)

Increased breathing rate - Your body tries to get more oxygen
Elevated heart rate - Heart works harder to deliver oxygen
Reduced plasma volume - Fluid shifts as body adjusts
Possible symptoms: Headache, mild fatigue, sleep disturbance

Short-Term Adaptations (Days to Weeks)

EPO release - Erythropoietin production increases
Red blood cell production - More oxygen-carrying capacity
Plasma volume recovery - Blood returns to normal volume
Metabolic adjustments - Improved oxygen extraction

Long-Term Adaptations (3+ Weeks)

Increased hemoglobin mass - Peak oxygen-carrying capacity
Capillary density - More blood vessels in muscles
Mitochondrial efficiency - Better cellular oxygen use
Reduced symptoms - Full adaptation to conditions

Timeline of Acclimation

Understanding the timeline helps you plan your approach:

Duration at Altitude	Adaptation Level	Performance Penalty
0-5 days	Acute stress	100% (full effect)
5-10 days	Early adaptation	~85% of full effect
10-21 days	Partial acclimation	~70% of full effect
21-28 days	Good acclimation	~50% of full effect
4+ weeks	Full acclimation	~50% of full effect

Note: Full acclimation doesn't eliminate the altitude penalty—it reduces it by about half.

The "Dead Zone" Problem

There's a timing issue that catches many runners:

Days 3-10 are often the worst for performance
Your body is stressed from acute exposure
Red blood cell adaptations haven't kicked in yet
Sleep quality is typically poor
Perceived exertion is high

This is why the standard advice is:

Arrive 1-2 days before a race OR 3+ weeks before—avoid the 3-14 day dead zone.

Live High, Train Low: The Gold Standard

Elite athletes often use "live high, train low" (LHTL) protocols for altitude training:

The Concept

Live at moderate altitude (2000-2500m) for 12-16+ hours daily
Train at lower altitude (<1500m) or with supplemental oxygen
Get altitude adaptation WITHOUT compromising training quality

Why It Works

Altitude exposure triggers EPO and red blood cell production
Training at altitude is compromised—you can't hit the same paces
LHTL provides both: adaptation stimulus + quality training

Practical LHTL Protocol

Week	Living Altitude	Training Altitude	Notes
1	2000-2500m	Easy only	Adjust to altitude
2	2000-2500m	Mix of descents	Add quality sessions at low alt
3-4	2000-2500m	Regular descents	Normal training pattern

Duration

Minimum: 3 weeks for measurable hemoglobin changes
Optimal: 4-6 weeks for best adaptation
Return: 2-3 weeks before major sea level competition

If You Can't Do LHTL

Not everyone has access to altitude camps. Here are alternatives:

Altitude Tents/Masks

Sleep in a hypoxic tent at simulated altitude
Can achieve some of the living-high benefits
Requires 8-12 hours daily exposure
Mixed research on effectiveness vs. real altitude

Intermittent Hypoxic Training

Short sessions (1-2 hours) at simulated altitude
Primarily for acclimatization, not adaptation
Useful in the 2 weeks before an altitude race
May reduce acute mountain sickness symptoms

Just Show Up Early

If you can't do structured altitude training:

Arrive 3-4 weeks before your race
Accept slower training for the first week
Gradually build quality as you adapt
This approach works, just less optimally than LHTL

Pre-Race Strategy for Altitude

Option A: Arrive Late (1-2 days before)

Best when:

You can't arrive 3+ weeks early
The race is at moderate altitude (1500-2500m)
You're well-prepared at sea level

How to execute:

Arrive no more than 48 hours before race
Keep pre-race activities minimal
Expect full altitude effect—plan pace accordingly
Hydrate aggressively

Option B: Arrive Early (3+ weeks before)

Best when:

You have the time and resources
The race is a high priority goal
Altitude is significant (2000m+)

How to execute:

Plan a build-up block at altitude
Easy first week, then gradually resume normal training
Include some quality sessions, adjusted for altitude
Consider descent workouts for key sessions

Training at Altitude: Practical Tips

Week 1: Adjustment Phase

Volume: Reduce by 25-30%
Intensity: Easy runs only
HR: Expect 10-15 beats higher for same effort
Sleep: May be disrupted—prioritize rest

Week 2: Transition Phase

Volume: Return to ~80-90% of normal
Intensity: Begin adding strides, light tempo
HR: Starting to normalize
Sleep: Should be improving

Week 3+: Training Phase

Volume: Normal or near-normal
Intensity: Resume quality sessions (adjusted paces)
HR: Close to normal response
Recovery: May need extra time between hard efforts

Pace Adjustments During Acclimation

Use these rough adjustments for training at 2000m:

Workout Type	Week 1	Week 2	Week 3+
Easy Runs	5-10% slower	3-5% slower	2-3% slower
Tempo	Avoid	8-10% slower	5-7% slower
Intervals	Avoid	6-8% slower	4-6% slower
Long Runs	8-10% slower	5-8% slower	3-5% slower

Better yet: Run by heart rate or effort rather than pace during acclimation.

Iron Status: The Hidden Factor

Your body needs iron to make new red blood cells. Before altitude training:

Pre-Altitude Checklist

Get ferritin levels tested
Target ferritin > 30 ng/mL (ideally 50+)
Consider iron supplementation if low
Address deficiency 4-6 weeks before altitude

Why It Matters

Low iron = can't make new hemoglobin
Altitude triggers EPO but body can't respond
Many runners (especially women) are iron deficient
This is a common reason altitude training "doesn't work"

Recognizing Altitude Sickness

Mild altitude sickness is common above 2500m. Watch for:

Acute Mountain Sickness (AMS)

Persistent headache
Nausea or loss of appetite
Dizziness or lightheadedness
Fatigue and weakness
Difficulty sleeping

When to Descend

Symptoms persist or worsen after 24-48 hours
Any signs of confusion or coordination problems
Difficulty breathing at rest
Symptoms of HAPE or HACE (medical emergencies)

Never ascend with symptoms—rest, hydrate, and descend if needed.

Hydration and Nutrition at Altitude

Increased Needs

Fluid: 25-50% more than sea level
Carbohydrates: Slightly higher utilization
Iron: Critical for adaptation
Antioxidants: May help with oxidative stress

Practical Tips

Carry water on all runs
Monitor urine color (pale yellow = good)
Eat well—altitude can suppress appetite
Avoid alcohol in first few days

Returning to Sea Level

After altitude training, performance typically follows this pattern:

Days Post-Altitude	Performance
0-3	Variable, often slightly worse
4-14	Good—optimal window for racing
14-21	Benefits starting to fade
21+	Returning to baseline

Timing Your Return

High-priority race: Return 7-14 days before
This gives: Time for travel recovery + peak hemoglobin benefits
Avoid: Racing within 2-3 days of descending (jet lag + adjustment)

Summary: Key Takeaways

Acclimation takes time: 3+ weeks for significant adaptation
Avoid the dead zone: Days 3-14 are worst for performance
LHTL works best: If you have access, use it
Check your iron: Critical for adaptation
Adjust training: Run by effort, not pace
Plan race timing: Arrive late OR very early
Prioritize health: Altitude sickness is real—listen to your body

Use the Altitude Running Calculator to predict your performance at different stages of acclimation.

Altitude Running Calculator - Pace conversion
Altitude Running Pace Chart - Quick reference tables
How Altitude Affects Running - The science
Running Heat Calculator - For hot, high-altitude locations