Your Body’s Journey to the Summit: The 3 Phases of Acclimatization Explained
At Mons Actividades de Montaña, we know that reaching the summit isn't just about physical strength; it's about a deep understanding of our own physiology.
Have you ever wondered what actually happens inside your body as you gain altitude? Based on the concepts of Dr. Javier Seufferheld, a physician at Aconcagua Provincial Park, we explain step-by-step how your body transforms to live and perform at high altitudes—and why our itinerary designs are your ultimate life insurance.
The Great Mountain Myth: "There is Less Oxygen"
There is a common belief that there is "less oxygen" in high mountains. In reality, the percentage of oxygen in the air remains exactly the same as at sea level: 21%. The real challenge you face is called hypobaric hypoxia. As we ascend, atmospheric pressure decreases, making it extremely difficult for your lungs and tissues to capture that oxygen. This pressure change is the biochemical "trigger" that forces your body to begin a complex and fascinating three-phase adaptation process.
Phase 1: Acute Acclimatization (The first few hours)
As soon as you reach high altitude, your body switches on its emergency mechanisms. In this initial phase, which lasts from a few hours to a few days, you will experience immediate physiological responses to compensate for the pressure:
- Breathing and Pulse: Your breathing quickens (hyperventilation), as do your heart rate and blood pressure. The body works extra hard to pump blood.
- Increased Urination: To compensate for the internal imbalance, your kidneys begin to excrete a greater amount of bicarbonate. This is why it is completely normal (and healthy) to notice a significant increase in trips to the bathroom at camp.
Phase 2: Subacute Acclimatization (The secret of our itineraries)
If you give your body time—gaining meters progressively as we do at Mons—you will enter a more advanced stage. From the first few days and over a couple of weeks, changes stop being "emergency-only" and shift to the bloodstream. An increase in red blood cell concentration occurs, and substances in the plasma are modified. These changes completely transform the efficiency with which your blood captures oxygen in the lungs and releases it into the muscles. This is why expeditions like Cerro del Medio, Vallecitos, or El Plata require several days of progressive trekking: we are giving your blood the exact time it needs to enter this phase.
Phase 3: Deep Acclimatization (Cellular transformation)
This is the stage where the true magic happens, reserved for prolonged expeditions like Aconcagua or the Himalayas. If you spend weeks at high base camps, cellular respiration transforms from within. The change occurs in the mitochondria (the engines of our cells). They modify their functionality to optimally use the little oxygen available and even increase in density, generating more "engines" per cell to become hyper-efficient.
Supercompensation: Your body upon returning home
This process at altitude generates an incredible, beneficial "supercompensation." When you return to urban life after traversing the mountains, you will notice your body performs spectacularly at sea level—whether running, training, or in your daily life. Your organism becomes a hyper-oxygenated machine. (Note: Extreme exposure has a limit. Doctors warn that staying for months at extreme altitude stops being beneficial and can lead to deterioration—hence the importance of descending to rest).
Why we don't "rush" the mountain at Mons
The path to high altitude is a lesson in patience. Now you understand why our expeditions don't try to "break summit records." We design the logistics of our camps (like Veguitas, El Salto, or the huts) specifically to align with your body’s biological timing. Respecting these 3 phases of adaptation is the true key to success. Give your body the time, hydration, and logistical care it needs, and we will take you to the top!