TL;DR
- Going to altitude is a real stressor. For many people, resting heart rate rises and HRV falls for a few days.
- Sleep often gets lighter at elevation, especially the first 1 to 3 nights.
- Expect easy pace to slow down at the same effort. Adjust pace and intensity, not your self-worth.
- The first week is about acclimatization: keep intensity low, nail hydration, and sleep as well as you can.
- Century is built to turn Apple Health signals into a practical plan when your environment changes.
Why your metrics change at altitude
At higher elevation, the air pressure is lower. That means there is less oxygen available per breath.
Your body compensates by:
- increasing breathing rate
- increasing heart rate
- shifting how your nervous system regulates stress and recovery
This is why altitude can show up in Apple Health even if you are not training harder.
The most common pattern
For many athletes, the first few days look like this:
- Resting Heart Rate: up
- HRV: down
- Sleep: more fragmented
- Workouts: feel harder at the same pace
This pattern can be normal and temporary.
What is normal vs what is a red flag
Normal (common) early acclimatization signs:
- mild headache
- higher resting heart rate for a few days
- reduced appetite
- easy workouts feeling harder
Red flags to take seriously:
- severe headache that does not improve
- nausea or vomiting
- dizziness, confusion, or severe fatigue
- shortness of breath at rest
If you have concerning symptoms, do not try to "tough it out". Seek medical advice.
How to adjust training for the first week at elevation
1) Treat altitude like extra training load
If your environment adds stress, your plan should subtract stress somewhere else.
Easy rule:
- keep hard workouts easy for 3 to 5 days
- keep easy days truly easy
2) Use effort and heart rate, not pace
At altitude, pace is often the first thing to change.
If you try to force sea-level pace, you will turn every run into a threshold session.
Instead:
- keep the talk test comfortable
- cap heart rate on easy days
- shorten long runs until you feel stable
3) Prioritize sleep quality inputs
Altitude can make sleep more fragile. Stack the basics:
- consistent bedtime
- cool, dark room
- earlier caffeine cutoff
- light dinner (avoid heavy late meals)
If you are traveling across time zones too, expect the first nights to be messy.
4) Hydrate, but do not overdo plain water
At altitude, many people breathe more and lose more fluid. Hydration helps.
But if you slam plain water without electrolytes, you can feel worse.
Practical approach:
- drink to thirst
- add electrolytes if you are training, sweating, or peeing constantly
5) Give yourself 7 to 14 days for full adaptation
Some metrics stabilize quickly. Others take longer.
Do not make permanent conclusions from three days of data.
What to track in Apple Health while you acclimate
If you want a simple dashboard, track these daily trend lines:
- Resting Heart Rate
- HRV
- Sleep duration
- Subjective notes (how you feel)
If your resting heart rate stays elevated and HRV stays suppressed for a week, that is a sign to reduce intensity further or add rest.
Two YouTube videos worth watching (altitude training and acclimatization)
Disclaimer: These are educational resources, not medical advice.
Checklist: altitude travel plan for endurance athletes
Before you go:
- plan a lighter first week (especially intensity)
- pack electrolytes
- plan sleep timing as a priority, not a bonus
Day 1 to 3:
- keep sessions short and easy
- do not chase pace
- take notes on sleep and symptoms
Day 4 to 7:
- add volume gradually
- add intensity only if resting heart rate and sleep are stabilizing
Next reads
- Travel and jetlag reset: the simple plan for athletes
- Resting heart rate trends: what is normal and what is not
- HRV and resting heart rate: train or rest?
Where Century fits
When your environment changes, your training plan should adapt. Most people do not have a simple way to connect:
- Apple Watch signals
- sleep trends
- training load
- real-world context like travel, altitude, and heat
Century is built to do exactly that.
Instead of guessing whether you should push or back off, Century helps you make a better call based on trends.