The Effect of Climbing Mount Everest on Spleen Contraction and Increase in Hemoglobin Concentration During Breath Holding and Exercise
Authors: Harald K. Engan, Angelica Lodin-Sundström, Fanny Schagatay, Erika Schagatay
DOI / Source: 10.1089/ham.2013.1061
Date: 01 January 2014
Reading level: Intermediate
Why This Matters for Freedivers
This paper suggests that living and working in low-oxygen environments for weeks (altitude acclimatization) can make your spleen “squeeze harder” during breath-holds and exercise. For freedivers, it helps explain why some people feel unusually strong in serial apneas after time at altitude—and it reinforces the broader idea that the spleen is a real, trainable contributor to short-term oxygen-carrying capacity.
Synopsis
Freedivers already know about the “spleen response”: do a few breath-holds and the spleen can contract, pushing extra red blood cells into circulation for a short time. That can slightly raise hemoglobin concentration and improve oxygen transport—helpful during repeated apneas. But what happens after long-term altitude exposure, when the body has been living in hypoxia for weeks and has already built more red blood cells overall. Does the spleen still behave the same, or does it change.
This study took advantage of a rare real-world situation: a team climbing Mount Everest (8848 m). The researchers tested the climbers before and after the expedition in the same lab setting in Kathmandu (1370 m). Eight climbers completed both tests.
What they did
The protocol was designed to trigger spleen contraction in two different ways:
1) Three maximal-effort breath-holds in ambient air, spaced by 2 minutes.
2) A short bout of cycling exercise (5 minutes at 100 W).
Throughout the protocol the team measured spleen volume repeatedly using ultrasound, and took finger capillary samples to measure hemoglobin concentration. Heart rate and oxygen saturation were recorded continuously.
They also included controlled breathing periods (including oxygen breathing) to standardize conditions and avoid Kathmandu’s mild altitude affecting the baseline.
What changed after Everest
Two big things were clear after the expedition:
1) Baseline spleen size didn’t change much.
Resting spleen volume before and after the climb was essentially similar.
2) The spleen contracted more strongly after the climb.
After three breath-holds, spleen volume was lower post-expedition than pre-expedition (a stronger contraction). The same pattern showed up after the exercise bout: spleen volume dropped much more after the climb than before it.
On top of that, baseline hemoglobin was much higher after the expedition, consistent with classic altitude acclimatization (more red blood cells overall). But the study’s most interesting finding wasn’t just “they had more blood” — it was that their spleen’s contractile response during breath-holding and exercise seemed enhanced and more persistent after long-term hypoxic exposure.
What didn’t change
Breath-hold duration and most cardiovascular responses didn’t show major differences between pre- and post-tests. That matters because it suggests the stronger spleen contraction wasn’t simply because they “tried harder” or had a stronger dive reflex on the day.
What it might mean
The authors interpret the findings as evidence that the spleen’s ability to contract can be augmented by altitude acclimatization, possibly because the body has been repeatedly pushed into low-oxygen states during prolonged physical work at altitude. They also note that the post-expedition spleen remained somewhat contracted and hemoglobin stayed elevated even after a recovery period, hinting that the spleen response may be more “efficient” after long-term hypoxic exposure.
Takeaway for freedivers
This study strengthens a practical idea: the spleen is not just a quirky lab effect—it responds to real hypoxic living conditions, and long-term hypoxia can make that response stronger. It also adds nuance: even if your baseline hemoglobin is already high (like after altitude), the spleen may still provide an extra short-term boost during breath-holds and exercise.
Abstract
Release of stored red blood cells resulting from spleen contraction improves human performance in various hypoxic situations. This study determined spleen volume resulting from two contraction-evoking stimuli: breath holding and exercise before and after altitude acclimatization during a Mount Everest ascent (8848 m). Eight climbers performed the following protocol before and after the climb: 5 min ambient air respiration at 1370 m during rest, 20 min oxygen respiration, 20 min ambient air respiration at 1370 m, three maximal-effort breath holds spaced by 2 min, 10 min ambient air respiration, 5 min of cycling at 100 W, and finally 10 min ambient air respiration. We measured spleen volume by ultrasound and capillary hemoglobin (HB) concentration after each exposure, and heart rate (HR) and arterial oxygen saturation (Sao2) continuously. Mean (SD) baseline spleen volume was unchanged at 213 (101) mL before and 206 (52) mL after the climb. Before the climb, spleen volume was reduced to 184 (83) mL after three breath holds, and after the climb three breath holds resulted in a spleen volume of 132 (26) mL. After exercise, the preclimb spleen volume was 186 (89) mL vs. 112 (38) mL after the climb. Breath hold duration and cardiovascular responses were unchanged after the climb. We concluded that spleen contraction may be enhanced by altitude acclimatization, probably reflecting both the acclimatization to chronic hypoxic exposure and acute hypoxia during physical work.