CoachingAnswer

HOW DO I PREPARE FOR A RACE AT ALTITUDE?

By Anthony WalshRoadman CyclingUpdated 26 May 2026

ANSWER

There are only two good ways to race at altitude: arrive at least 14 days early so red blood cell mass has adapted, or race within the first 24 hours before the acute performance dip lands at days 3–5. Arriving 3–7 days out is the worst window — you carry the cost of thin air without the haematological payoff. Whichever you choose, drop power targets 6–10% above 1,800m and front-load hydration.

KEY TAKEAWAYS

Two viable windows: 24 hours before arrival fatigue, or 14+ days after full acclimatisation. Avoid days 3–7.
Power drops roughly 6–10% per 1,000m above 1,500m — pace by feel and heart rate, not sea-level watts.
Altitude dehydrates faster: respiratory water loss and higher breathing rates push fluid needs up 20–30%.
A pre-trip heat block or altitude-tent block primes the haematological system before you ever arrive.

WHO THIS IS FOR

IS THIS YOU?

The amateur travelling to a high-altitude gran fondo

Leadville, the Haute Route, a Pyrenean or Alpine sportive — events that finish above 2,000m and punish riders who arrive unprepared.

The rider who can only arrive a few days before

Work and life mean you can't get there two weeks early. You need to know how to race in the worst acclimatisation window without blowing up.

THE ROADMAN VIEW

Here's the thing nobody tells you about altitude races: the timing of your arrival matters more than almost anything you do in training. There are two windows that work and one that wrecks you. Land the day before and race within 24 hours — you've not yet hit the acute fatigue that altitude dumps on you around days 3 to 5. Or commit to arriving two weeks out and let your body actually build the red cells. The trap is the middle: showing up four or five days before, which is exactly when most amateurs book their flights, and racing straight into the worst of the adjustment.

Anthony has dug into this on the podcast through the altitude-camp conversations with coaches like Dan Lorang. The pros don't roll the dice on this. They either live at altitude for weeks before a high mountain Grand Tour, or they manage the descent-and-recovery timing precisely. The amateur version is the same logic scaled down — you just have fewer weeks to play with, so you have to be deliberate about which window you're targeting.

The free adaptation most amateurs skip is priming the system before they travel. A 10–14 day heat block at home, or an altitude-tent block if you have access, gets some of the plasma volume and red cell work done in advance. You arrive partway adapted instead of starting from zero. It won't replace genuine altitude exposure, but it shrinks the hole you're climbing out of when the air gets thin.

EXPERT EVIDENCE

WHAT THE EXPERTS SAY

Dan LorangHead of Performance, Red Bull–Bora–Hansgrohe; coach to Jan Frodeno and Anne Haug
World Tour teams treat altitude-race timing as a planned variable, not a hope. The haematological adaptation that matters takes 2–3 weeks to build, so riders either commit to that full window or manage the acute phase deliberately. Arriving mid-acclimatisation, when the body is still adjusting and performance is suppressed, is the scenario coaches work hardest to avoid.
Hear it: 13 Years Of Coaching Pros: What Amateurs Don't Know
Dr Benjamin LevineDirector, Institute for Exercise and Environmental Medicine; lead researcher on live-high train-low altitude protocols
Acute exposure to altitude produces a well-documented performance dip that bottoms out around days 3–5 as the body downregulates plasma volume before red cell mass rises. The practical consequence: a rider racing in that window performs worse than they would have on either arrival day or after two weeks of acclimatisation.

PRACTICAL APPLICATION

DO THIS WEEK

Pick your arrival window deliberately
If you can arrive 14+ days before the event, do it — that allows red blood cell adaptation. If you can't, arrive within 24 hours of the start and race before the acute dip lands. Do not arrive 3–7 days out; it's the worst of both worlds.
Recalibrate your power targets
Expect to lose roughly 6–10% of sustainable power per 1,000m above 1,500m. At 2,500m that's a meaningful chunk. Race by heart rate and perceived effort rather than chasing your sea-level numbers — the watts simply will not be there, and forcing them is how you blow up early.
Increase fluid intake by 20–30%
Altitude air is dry and your breathing rate climbs, so respiratory and urinary water losses rise. Add 20–30% to your normal daily fluid intake from the day you arrive, with electrolytes, and monitor urine colour. Dehydration at altitude compounds the performance hit fast.
Prime the system before you travel
Run a 10–14 day heat block or altitude-tent block ending the week before you leave. This pre-builds some plasma volume and red cell adaptation, so you arrive partway acclimatised rather than starting the clock at zero.

COMMON MISTAKES

WHAT CYCLISTS GET WRONG

MISTAKEArriving 4–5 days before the race.
FIXThis is the acute fatigue window — your body has downregulated plasma volume but not yet built red cells. Either arrive 24 hours out, or commit to 14+ days early. The middle window is the one to avoid.
MISTAKERacing to sea-level power numbers at altitude.
FIXYour sustainable power drops 6–10% per 1,000m of elevation. Pace by heart rate and feel for the first part of the race. Chasing familiar watts at 2,500m guarantees an early implosion.
MISTAKEHydrating as if you were at sea level.
FIXDry air and elevated breathing rates increase water loss significantly. Add 20–30% to your fluid intake from arrival, include electrolytes, and check urine colour daily.

FAQ

FREQUENTLY ASKED QUESTIONS

How early should I arrive before a high-altitude race?

Either 24 hours before, to race ahead of the acute fatigue that lands at days 3–5, or at least 14 days before, to let red blood cell mass adapt. The window between those two — roughly days 3 to 7 — is where performance is most suppressed, so avoid arriving then.

How much slower will I be at altitude?

Sustainable power drops roughly 6–10% per 1,000m above 1,500m. At 2,500m an unacclimatised rider might lose 12–18% of sea-level power. The effect is steeper for harder efforts above threshold, where oxygen delivery is the hard limiter.

Does sleeping at altitude before the race help?

Yes, if you have enough time. Sleeping at 2,000m+ for two weeks or more drives the red blood cell adaptation that protects performance. A few nights does little for red cells but does begin the acclimatisation that reduces acute altitude sickness symptoms.

Can I use an altitude tent to prepare for an altitude race?

Yes. Sleeping in an altitude tent at simulated 2,500–3,000m for 3–4 weeks before travelling pre-builds some red cell adaptation, so you arrive partway acclimatised. It requires consistent nightly use to work — sporadic use costs sleep quality without delivering the adaptation.

Should I change my fuelling for an altitude race?

Carbohydrate needs stay broadly the same, but appetite is often suppressed at altitude, so deliberate fuelling matters more. Hydration needs rise 20–30%. Iron status also matters — red cell production depends on it, so check iron levels well before an altitude block if you're adapting in advance.

Will altitude sickness affect my race?

Mild acute mountain sickness — headache, poor sleep, breathlessness — is common in the first 24–72 hours above 2,500m and can blunt performance. Arriving early enough to move through it, staying well hydrated, and avoiding hard efforts in the first days reduces the risk. Severe symptoms mean descend, not race.

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