You can trigger many of the same physiological adaptations that happen at altitude without leaving sea level. The key is exposing your body to reduced oxygen, whether through hypoxic equipment, breathing techniques, or complementary strategies like heat training. None of these perfectly replicate living at 8,000 feet, but each method nudges your body toward producing more red blood cells, expanding blood volume, or improving your tolerance for low-oxygen environments.
What Altitude Does to Your Body
At elevation, the air contains less available oxygen. Your kidneys respond by ramping up production of a hormone called EPO, which signals your bone marrow to produce more red blood cells. More red blood cells means more hemoglobin, the protein that carries oxygen to working muscles. EPO levels peak within one to three days of altitude exposure, then gradually decline over the following weeks, though they stay above baseline for some time. The downstream result, an increase in total hemoglobin mass and red blood cell volume, typically requires at least three weeks of consistent exposure to become meaningful.
This is the adaptation endurance athletes chase. In studies of elite biathletes training at roughly 6,700 feet for three weeks, total hemoglobin mass increased by about 9% in men, and red blood cell volume rose from around 39 to 43.5 mL per kilogram of body weight. Those changes translate directly to better oxygen delivery during hard efforts.
Hypoxic Tents and Rooms
The most direct way to simulate altitude at sea level is a hypoxic tent or chamber that reduces the oxygen concentration in the air you breathe. These systems pump nitrogen-enriched air into an enclosed sleeping space, dropping the effective oxygen level to mimic elevations of 6,500 to 9,000 feet. The idea follows the “live high, train low” model: you sleep in thin air to stimulate red blood cell production but do your hard workouts in normal oxygen so training quality stays high.
For this approach to work, the research consistently points to a minimum of 12 to 14 hours per day in the hypoxic environment, typically overnight plus additional resting hours. Duration matters too. Interventions lasting longer than three weeks produce significantly greater improvements in hemoglobin levels and aerobic capacity compared to three-week blocks. If you’re investing in a hypoxic tent, plan on using it nightly for at least four weeks to see real hematological changes.
Hypoxic tents are expensive, often $2,000 to $5,000 or more, and can be noisy and uncomfortable for sleep. Renting is an option through several specialty companies. The payoff is real but requires disciplined, sustained use.
Intermittent Hypoxic Training
A more accessible alternative is intermittent hypoxic training, where you breathe low-oxygen air through a mask or mouthpiece connected to a hypoxic generator during short sessions. These typically last less than two hours, two to five times per week, and can be done either at rest or while exercising. Blood oxygen saturation during these sessions often drops to the 78 to 95% range, depending on the protocol.
The sessions alternate between periods of breathing hypoxic air and normal air, creating repeated cycles of oxygen stress and recovery. Some protocols have you sit quietly while breathing through the device (intermittent hypoxic exposure), while others incorporate exercise like cycling or running on a treadmill (intermittent hypoxic training). The exercise-based approach tends to produce more robust performance improvements because you’re combining the oxygen stress with a training stimulus.
You can find intermittent hypoxic training at specialized sports performance centers, altitude training studios, or through portable hypoxic generators designed for home use. These generators are less expensive than full tent setups, though still a significant investment.
Why Elevation Masks Fall Short
Elevation training masks, the neoprene devices with adjustable valves that restrict airflow, are marketed as altitude simulators. They don’t deliver. A study measuring their effects found no significant changes in hemoglobin, hematocrit, or lung function after a training block with the mask. Blood oxygen saturation during exercise was only about 2% lower in mask wearers compared to controls (94% versus 96%), far less than the drops seen with genuine hypoxic devices.
What these masks actually do is make it harder to breathe in, essentially functioning as respiratory muscle trainers. That’s not worthless. Stronger breathing muscles can reduce the sensation of effort during hard exercise. But if your goal is to boost red blood cell production or genuinely prepare your body for altitude, an elevation mask won’t get you there. Save the money for a real hypoxic device or use the breathing techniques described below.
Breath-Hold and Hypoventilation Training
You can create brief, self-generated episodes of low oxygen through controlled breathing techniques during exercise. The most studied approach is voluntary hypoventilation at low lung volume: you exhale to a comfortable low point, hold your breath for 4 to 8 seconds while continuing to move (running, cycling, or swimming), then exhale any remaining air and breathe freely for a short recovery period of 16 to 30 seconds before repeating the cycle.
This technique drives blood oxygen saturation below 88% during repeated efforts, enough to create genuine hypoxic and hypercapnic (high carbon dioxide) stress. Swimmers have used this extensively, holding their breath for set distances like 15 to 40 meters during sprint intervals. Runners and cyclists can apply the same principle during short repeats.
The primary benefit is improved tolerance to the discomfort of low oxygen and high carbon dioxide, the exact sensations that overwhelm you at altitude. Long-term practice builds your body’s comfort operating in oxygen-depleted states. This won’t increase your red blood cell count the way weeks of sleeping in a hypoxic tent will, but it sharpens your ability to perform when breathing gets hard, and it costs nothing.
Heat Training as a Complement
Training in hot conditions produces overlapping adaptations with altitude exposure. Heat acclimation expands plasma volume by roughly 6.5%, increases maximal cardiac output by about 9% in cool conditions, and reduces oxygen demand at a given effort level. It also spares muscle glycogen and lowers blood lactate during exercise. These are many of the same performance markers that improve with altitude training, delivered through a different stress.
Heat acclimation won’t boost red blood cell production the way true hypoxic exposure does. But the cardiovascular improvements, particularly the expanded blood volume and improved cardiac efficiency, provide a meaningful performance foundation. If you’re preparing for a high-altitude event, combining heat training with one of the hypoxic methods above covers more physiological ground than either approach alone. Practically, this means doing some training sessions in warm environments (overdressing for runs, using a heated room on the bike trainer) for 10 to 14 days before your altitude exposure.
Get Your Iron Stores Right
None of these strategies work if your body lacks the raw materials to build new red blood cells. Iron is the critical ingredient, and low iron stores can completely blunt the altitude response. In a study tracking athletes at altitude for four weeks, those with low ferritin levels (below 30 ng/mL for men, below 20 ng/mL for women) showed no increase in red blood cell volume or aerobic capacity. Athletes with adequate iron stores increased both significantly.
The recommended target before any altitude or hypoxic training block is a serum ferritin level between 40 and 90 ng/mL. Get your ferritin tested well in advance, ideally six to eight weeks before you start, since building iron stores takes time. Many endurance athletes, particularly women and vegetarians, run chronically low without knowing it. If your levels are insufficient, iron supplementation paired with vitamin C for absorption can bring you into range, but this is worth working through with a healthcare provider since excess iron carries its own risks.
Planning Your Timeline
If you’re preparing for a race or trek at altitude, start your sea-level altitude training at least four to six weeks before the event. The research is clear that interventions lasting longer than three weeks produce more substantial improvements in both blood markers and actual performance compared to shorter blocks. A realistic timeline might look like this: begin iron optimization eight weeks out, start intermittent hypoxic sessions or tent use six weeks out, and layer in heat training during the final two to three weeks.
For the budget-conscious athlete without access to hypoxic equipment, combining breath-hold training during interval sessions with heat acclimation work still provides meaningful preparation. You won’t get the red blood cell boost, but you’ll arrive at altitude with better cardiovascular efficiency, expanded plasma volume, and a nervous system more comfortable operating under respiratory stress. That combination meaningfully reduces the performance drop most people experience in their first days at elevation.