What altitude actually does to your body
At 2,400 metres above sea level, the atmosphere contains roughly 16% less oxygen per breath than at sea level. That sounds like a disadvantage — and in the short term, it is. Your power output drops, your perceived effort spikes, and recovery slows. But your body notices the shortfall and gets to work. Within days, your kidneys increase erythropoietin (EPO) production, triggering the creation of new red blood cells and expanding your haemoglobin mass. More haemoglobin means more oxygen-carrying capacity. More oxygen-carrying capacity means higher VO₂max when you return to lower elevation. That's the whole point.
A 2023 meta-analysis published in PMC confirmed that altitude training produces statistically significant increases in both VO₂max (SMD = 0.67) and haemoglobin levels (SMD = 0.50) compared to training at sea level. These aren't marginal gains — for a competitive amateur cyclist, this is the equivalent of weeks of additional structured work compressed into a single training block. If you're serious about periodising your season, understanding altitude camps belongs in the same conversation as polarised training methodology, not as a separate exotic practice.
How to structure an altitude camp that actually works
The gold standard in current research is the Live High, Train Low (LHTL) model. You sleep and rest at altitude — typically between 2,000 and 2,500 metres — while descending to lower elevation for your actual training sessions. The logic is elegant. Sleeping at altitude drives haemoglobin adaptation. But training at altitude forces you to work at lower absolute intensities because of the reduced oxygen availability, which means your muscles don't get the high-power stimulus they need. LHTL sidesteps that compromise entirely.
The research is fairly consistent on duration. Sixteen to twenty-one days seems to be the productive window. Some athletes see a drop-off in adaptation after three full weeks — the body starts to plateau and the accumulated fatigue from disrupted sleep and suppressed recovery begins to outweigh the benefits. A four-week camp at 2,454 metres was studied by Chinese researchers and produced the best aerobic outcomes in their cohort, but that's an upper bound, not a target for everyone. For most serious amateurs, a well-structured 18-day camp at around 2,300 metres will do the job.
What you train matters as much as where you sleep. Altitude suppresses your ability to produce high-intensity efforts, so this is not the time to pile on threshold intervals. Low-to-moderate intensity volume — Zone 2 work, long aerobic rides — benefits most from the hypoxic environment. The high-end intensity work should wait until you're back at sea level, where you can actually produce the power outputs the training demands. This principle of matching training stress to environmental conditions is central to how structured cycling training works at every level of the sport.
The timing problem: when to compete after altitude
Let's be honest: this is where most athletes get it wrong, and it's the detail that separates a useful altitude camp from an expensive one. The haematological adaptations — the extra red blood cells — don't just appear fully formed the moment you descend. They take time to consolidate, and they also decay once you return to sea level. Research consistently points to two performance windows: the first week after returning (when ventilatory adaptations are still high but haematological gains are freshly in place), and a second window around three to four weeks post-return (when haemoglobin mass is still elevated but the ventilatory cost of exercise has normalised).
The two weeks in between? That's the dip. Many athletes return from altitude feeling flat, stale, and slower than before they left. This is normal. It's physiological, not psychological. The ventilatory adaptations that made you feel "efficient" at altitude are fading faster than the blood adaptations are settling in. If you have a major event, you want to land on one side of that dip or the other. Either race within the first seven days of return, or give yourself a full three weeks back at sea level. Scheduling a gran fondo or sportive at day 11 post-camp is the worst possible outcome.
The same timing logic applies if your event is at altitude. Arriving two to four days before a high-altitude race is the worst-case scenario — that's the window of maximum fatigue and lowest performance. Arrive either the day before (and accept that you won't be fully acclimatised, but you'll be rested) or plan to be on-site for at least seven days beforehand, ideally more. Altitude sickness and dehydration are real risks in the first 48 hours that can derail a preparation entirely regardless of how well your training has gone.
The mistakes worth avoiding
Going too high is a surprisingly common error. Above 3,000 metres, sleep quality deteriorates sharply, recovery slows, and the risk of altitude sickness increases. The sweet spot of 2,000 to 2,500 metres is not arbitrary — it's where the hypoxic stimulus is strong enough to trigger adaptation without overwhelming your system. Some camps advertise impressive elevations; that's not a selling point from a physiology standpoint.
Going for too short a period is equally counterproductive. A five-day trip to a ski resort at 1,400 metres is a holiday, not altitude training. The physiological adaptations don't kick in meaningfully until around five to seven days, which means you need a minimum of two weeks just to get into the productive window. A single week at a modest elevation produces almost no measurable haematological change.
Neglecting nutrition is the third common failure. Altitude increases your iron demand significantly — EPO production is useless without adequate iron to build new red blood cells. Athletes who arrive iron-depleted, or who don't actively manage iron intake during the camp, often see minimal gains despite doing everything else correctly. A baseline ferritin check before any altitude block is worth the small inconvenience. Similarly, hydration management matters more at altitude because of increased respiratory water loss; mild chronic dehydration is common and blunts adaptation.
Finally, some riders treat altitude training as a shortcut around consistent structured work. It isn't. Altitude amplifies the adaptations you've already built. An athlete who arrives at a camp with a well-developed aerobic base — ideally coming off a solid block of environmental adaptation training — will respond better than one who's been inconsistent. The haematological gains are real, but they sit on top of your existing physiology. Build the base first, then use altitude to push it further.
Making altitude work within an adaptive training plan
For most serious amateur cyclists, altitude training is a once-or-twice-a-year intervention, not a year-round strategy. Placed correctly in the season — typically four to six weeks out from a key event, followed by a structured return block — it can meaningfully improve your result at that event. Placed randomly, rushed, or without attention to the timing windows described above, it won't move the needle and may leave you fatigued when it matters most.
The planning complexity here is real. You need to account for your current fitness, the date of your target event, travel logistics, the return timing windows, and your ongoing training structure. A structured plan that keeps a clear shape but can adjust as your fitness evolves — rather than a fixed 12-week spreadsheet you can never revisit — handles this kind of periodisation more reliably. When an altitude block sits inside a plan that can respond to how you actually feel and recover post-camp, you stop guessing about the timing: the plan flags what it notices, and you and your coach make the call together.
Related reads
Polarised training for cyclists
Structured cycling training
Heat adaptation for cyclists
Sources
Garvican-Lewis et al. (2023). Effect of altitude training on the aerobic capacity of athletes: A systematic review and meta-analysis. PMC / PLOS ONE. pmc.ncbi.nlm.nih.gov
Chapman et al. (2014). Timing of return from altitude training for optimal sea level performance. Journal of Applied Physiology. journals.physiology.org
Hamlin et al. (2024). Carbon monoxide supplementation and altitude training effects in elite cyclists. Journal of Applied Physiology. journals.physiology.org