The Red Blood Cell Claim, Checked
You will hear it everywhere: hold your breath and your body makes more red blood cells, just like altitude.
Part of that is grounded in real physiology. Part of it runs well ahead of the evidence.
Coaches and sports scientists deserve the full picture, so here is what the studies actually measured, and what they did not find.
The Spleen Response Is Real
The spleen stores red blood cells. During a breath hold, it can contract and push some of them into circulation.
Persson and colleagues (2023) measured this in 18 people. After a breath hold of around 137 seconds on average, spleen volume was about 21% smaller than at rest, and haemoglobin rose by 2.4%.
This is an acute effect. It describes what happens around a set of breath holds, not a lasting change in how much blood an athlete carries.
The EPO Signal: Present, But Inconsistent
EPO, or erythropoietin, is the hormone that signals the body to produce red blood cells. This is where the evidence gets mixed.
De Bruijn, Richardson and Schagatay (2008) had 10 healthy volunteers perform 15 maximal breath holds in three series. Serum EPO rose by an average maximum of 24% compared with baseline.
Elia and colleagues (2019) compared elite breath hold divers with non divers. In the elite divers, EPO rose from 6.85 to 10.87 mIU/mL three hours after the holds, an increase of 63%.
Those elite divers reached very low blood oxygen, with end of hold saturation averaging 62% during dynamic holds. Lower oxygen at the end of the hold was associated with a larger EPO rise.
But Bouten and colleagues (2022) found something different. Their breath hold test protocol did not raise EPO in 22 men, either before or after a six week training block.
So an EPO response can occur. Whether it does seems to depend on how deep the hypoxia goes, and many protocols may not go deep enough.
Does It Add Up To More Red Cells?
A short spike in EPO is not the same as more red blood cells. What matters for performance is whether training changes the blood over weeks.
Elia and colleagues (2021) trained eight non divers with ten maximal dynamic breath holds, four times a week for six weeks. EPO was raised only after the first session.
Reticulocytes, the young red blood cells, did increase, from 57 to 72 × 10⁹/L after week one, and again after week six. But mature red cell count, haemoglobin and spleen volume did not change.
Bouten and colleagues (2022) ran six weeks of daily static breath holds, five maximal holds a day. Haemoglobin mass did not change. Neither did VO2peak or 3 km cycling time trial performance.
That is the honest state of play. There is a signal in reticulocytes in one small study, but no study here showed an increase in haemoglobin or red cell mass after weeks of breath hold training.
So Why Train Breath Holds At All?
Because the strongest evidence for breath hold training in sport is not about the blood.
Repeated sprint training with breath holds at low lung volume has improved fatigue resistance and repeated sprint outcomes in team sport athletes. That is a training stimulus during the session, not a red cell adaptation.
In Vincere Protocol, we sell breath holds on what they have been shown to do. We do not promise a natural EPO boost, and you should be sceptical of anyone who does.
Reading The Research Like A Sports Scientist
When you see a breath hold claim, check four things.
Who was studied? Elite breath hold divers who train for years to tolerate extreme desaturation are not the same as a rugby squad doing a few weeks of holds.
What was measured? A rise in EPO in the hours after a session is a signal. A change in haemoglobin mass after weeks of training is an adaptation. They are not interchangeable.
How deep was the hypoxia? Across these studies, the strongest responses appeared where blood oxygen fell furthest. Gentle holds at rest may not reach that point.
How big was the study? Several of these trials had between 8 and 22 participants. Small studies can miss real effects, and they can also produce findings that do not repeat.
Applying that filter is what separates a credible breath program from marketing. It is also how staff protect athletes from chasing adaptations that may never arrive.
What This Means For Your Squad
If your goal is more red cell mass, the evidence here does not support breath holds as the tool.
If your goal is a hypoxic training stimulus during sprint sessions, breath holds at low lung volume have a stronger case, and that is where we focus.
Set the expectation clearly with athletes from day one. It builds trust in the program and keeps the work honest.
It also keeps the focus on outcomes your staff can actually measure in training, such as repeated sprint performance, rather than blood markers that may never shift.
And if a squad does want to monitor blood changes, that work belongs with qualified medical and sports science staff, using proper testing rather than assumptions.
Safety: breath hold training is done on land only. Never in or near water, never while driving, never alone. Stop if you feel dizzy. Seek medical clearance first if you are pregnant or have a heart, lung or blood pressure condition.
FOR ELITE ATHLETES, THIS CAN HELP YOU
✔ Understand the acute spleen response that follows a series of breath holds
✔ Know that EPO responses have been recorded, mainly with deep desaturation
✔ Set realistic expectations: weeks of breath hold training have not been shown to raise haemoglobin or red cell mass
✔ Separate the hype from the training effects breath holds can deliver
Performance takeawayThe spleen response is real. The red cell claim is not proven.
Control your breath. Control the result.
Want this in your program? Enquire about Vincere Protocol for your team.
