🫁 The Hidden natural blood reservoir
"I held my breath for over four minutes on an exhale."
In the days before his Era Vella send, Emmett paired cold water immersion with a structured breathwork protocol — two minutes of hyperventilation followed by an exhale breath-hold, repeated five times.
Tim Emmett, in Climbing · November 2025 · Era Vella 9aTim's four-minute exhale hold before his Era Vella send is consistent with the spleen priming mechanisms reviewed in Elia & Lemaître, European Journal of Applied Physiology, 2025 — and with the broader breath-hold physiology literature. Whether his breathwork preparation directly contributed to his performance remains an open question, but the timing and method are striking.
🩸 The Spleen: Your Body's Secret O₂ Reserve
The human spleen stores approximately 200–300 ml of blood with a hematocrit approaching 80% — roughly twice the concentration of red blood cells circulating in the rest of the body (Koga, 1979). It acts as a natural blood reservoir, waiting to be deployed under physiological stress.
💧 What the Spleen Stores
200–300 ml of oxygen-rich blood at ~80% hematocrit — double the normal circulating concentration of red blood cells.
⚡ What Triggers Release
Apnea → O₂ falls, CO₂ rises → chemoreceptors fire → sympathetic activation → spleen contracts → erythrocytes flood the bloodstream.
During breath holding, this sequence unfolds within minutes and the effect can persist for 5–10 minutes post-hold (Overgaard et al., 2020). The result is a temporary but meaningful increase in circulating haemoglobin and oxygen transport capacity.
"The spleen contracts, concurrently releasing its stored erythrocytes into the systemic circulation."— Elia & Lemaître · European Journal of Applied Physiology, 2025
📊 Performance Impact: What the Research Shows
| Mechanism | Effect | Duration | Magnitude |
|---|---|---|---|
| Splenic contraction | ↑ circulating Hb | 5–10 min post-hold | 3–8 g/L extra Hb |
| Hematocrit increase | ↑ O₂ transport capacity | Up to ~3 hours | 3.3–6.4% increase |
| Spleen volume reduction | ↑ erythrocyte release | Minutes of apnea | Up to 20% volume decrease |
| Bradycardia effect | ↓ HR, ↑ vagal tone | Immediate post-hold | Recovery cue for HRR₆₀ |
| EPO stimulation | Long-term RBC production | Weeks of training | Adaptation benefit |
🧗 Why This Matters Specifically in Climbing
Climbing creates uniquely favourable conditions for splenic response. During maximal efforts climbers hold their breath for multiple reasons:
- → Valsalva-like bracing during lock-offs, dynos, and powerful moves
- → Trunk stabilisation to maintain body tension on small footholds
- → Concentration and fear response — the nervous system naturally restricts breathing under stress
- → Minimising torso movement on balance-critical sequences
"The spleen has for centuries been considered to act as a dynamic reservoir. Breath-hold apnea has been shown to reduce spleen volume, releasing stored, oxygen-rich red blood cells into circulation."— Inoue et al. · Effect of Breath Holding on Spleen Volume Measured by MRI
Elite freedivers and some endurance athletes often demonstrate larger spleen volumes and greater splenic contraction than untrained individuals, although the extent to which this reflects training adaptation, genetics, or both remains under investigation.
🫁 The Pranaclimb cMBT — Climbing Maximum Breathlessness Test
The Pranaclimb cMBT is a field-based assessment developed to estimate functional breathlessness tolerance in climbers. It measures tolerance to breathlessness under load — a critical limiter in climbing. In climbers, breathlessness is rarely about oxygen shortage alone. It reflects CO₂ tolerance, chemoreflex sensitivity, diaphragm control under tension, and the ability to stay calm during pump, fear, and crux effort.
How to Perform the cMBT (Off the Wall)
- 1 Stand upright and relaxed
- 2 Exhale normally through the nose — do not force it
- 3 Pinch your nose to hold the breath
- 4 Walk at a normal, relaxed pace
- 5 Count your steps until the first clear urge to breathe
- 6 Stop immediately — do not push into distress
👉 The number of steps = your cMBT score. This test is about control, not suffering.
Pranaclimb cMBT Scale (Climbing-Specific)
| cMBT Score | Zone | Interpretation | What This Means for Climbing |
|---|---|---|---|
| <25 steps | 🔴 Low | Poor CO₂ tolerance | Early panic breathing, rapid BR spikes, poor crux composure |
| 25–40 | 🟠 Limited | Struggles above CP | Breathlessness dominates; Grey Zone feels chaotic |
| 40–60 | 🟡 Moderate | Functional | Short cruxes ok; breath control fades late in climbs |
| 60–80 | 🟢 Good | Strong control | Better pacing and recovery; strong near CP |
| 80+ | 🔵 Elite | Exceptional | Delayed RCP; calm under pump; strong redpoint resilience |
Progress is typically visible within 3–6 weeks with exhale holds, apnea walking, extended exhales, and controlled expressive breathing.
🔹 The Pranaclimb Breath-Hold Coaching Module
Breath holds are not just errors in BR data — they are a trainable strategy for pre-climb readiness, mid-crux stability, and recovery. Pranaclimb distinguishes three types:
| Type | Where It Happens | Coaching Focus | RBA Adjustment |
|---|---|---|---|
| Crux Hold | Involuntary during effort (lock-off, dyno, max tension) | Keep short (≤2s), release with grunt/exhale | +2 to +10 BPM (by duration) |
| Priming Hold | Pre-climb warm-up, controlled max hold | Boost O₂ buffering, splenic release | Flag only — not added to BR |
| Recovery Hold | Post-crux sigh + short exhale pause | Downregulate HR, parasympathetic reset | No upward adjustment |
Protocol A — Pre-Climb Spleen Priming
🔹 3–5 minutes before your redpoint attempt
2–3 deep breaths → exhale → max comfortable breath hold (after inhale)
3 rounds · 2 min full recovery between holds
Effect: Splenic contraction → temporary ↑ haemoglobin · mild O₂ buffering · effect lasts ~10 min
Cue: "Settle into calm. Inhale full, hold, notice the urge rising — then recover completely."
Protocol B — Crux Management
🔹 On the wall — high-tension moves
Allow ≤2s breath hold for stability on powerful moves
Release with forceful grunt or exhale to stabilise and re-oxygenate
Cue: "Hold to stabilise — then exhale with power as you move."
Protocol C — Recovery After Crux
🔹 At shake-outs, clips, and rests
3 sighs → short exhale hold (1–2s) → nasal inhale
Repeat ×3–4 after a crux or clip
Effect: Combines vagal reset (sigh) + bradycardia (BH) → faster HRR₆₀ and W′bal recharge
Cue: "Sigh out tension, pause, then breathe calm back in."
🔗 How This Fits the Pranaclimb Stack
🫁 cMBT (off wall)
Sets your breathlessness tolerance baseline — the size of your container.
📊 BR + RPE (on wall)
Show how fast you approach your limit — how quickly the container fills.
😤 Expressive breathing (on wall)
Shows how you cope when you are near the limit — grunts, screams, holds.
❤️ HRR₆₀ (post wall)
Shows how well you recover afterward — and how fast the container empties.
"The Pranaclimb cMBT is performed off the wall to isolate CO₂ tolerance, but interpreted on the wall to understand composure, pacing, and panic near CP and RCP."— Pranaclimb
⚠️ Safety: Never push breath holds to blackout — in training or on the wall.
⚠️ Use controlled environments for longer holds. Supervised sessions recommended for advanced apnea training.
⚠️ Optional pulse oximeter monitoring for elite athletes and longer protocols.
References
- Elia, A., & Lemaître, F. (2025). The application of breath-holding in sports: physiological effects, challenges, and future directions. European Journal of Applied Physiology, 125(8), 2049–2065. https://doi.org/10.1007/s00421-025-05752-y
- Inoue, Y., Nakajima, A., Mizukami, S., & Hata, H. (2013). Effect of breath holding on spleen volume measured by magnetic resonance imaging. PloS One, 8(6), e68670. https://doi.org/10.1371/journal.pone.0068670
- Koga, T. (1979). Splenic hematocrit reference values. American Physiological Society Journal.
- Overgaard, K. (2020). Spleen contraction occurs within minutes of apnea onset and lasts 5–10 minutes.
- Schagatay, E. (2001). Repeated apnea induces spleen contraction, raising Hb and improving oxygen availability.