At Pranaclimb, we use breathing rate (BR) not just as a signal of exertion, but as a window into your body's internal state — especially CO₂ regulation. CO₂ is one of the most powerful drivers of breathing and performance in climbing. Three tests help us map your relationship with it.
🔵 MBT — Maximal Breathlessness Step Test
Type: Dynamic Movement-Based CO₂ Tolerance Test
The MBT tests how well a climber tolerates breathlessness during actual movement — directly reflecting crux performance, BR spikes, and W′bal depletion. It's the Pranaclimb primary diagnostic.
What it Measures
Breathlessness tolerance during movement · CO₂ accumulation under exercise · Anaerobic resilience · Crux-style discomfort tolerance
Best For
Hard redpoint sequences · Boulder circuits · Identifying climbers who "panic breathe" under load · Pre-RBA diagnostic
🟢 BOLT — Body Oxygen Level Test
Type: Static, Resting CO₂ Tolerance Test
The BOLT is your daily respiratory efficiency score — a simple, resting breath-hold test that tracks progress over weeks and months of breathwork training.
What it Measures
Basic chemoreceptor sensitivity · Breath-hold comfort · Nasal breathing ability · Baseline respiratory efficiency
Best For
Morning assessments · Recovery days · Baseline tracking in RBA · Monitoring long-term breathwork progress
🟣 Huberman CO₂ Tolerance Protocol
Type: Controlled breath-holding for stress regulation
The Huberman Protocol trains your psychological response to rising CO₂ — building composure, focus under discomfort, and parasympathetic switching. It's the mental performance tool of the three.
What it Measures/Trains
Psychological response to rising CO₂ · Focus under discomfort · Sympathetic/parasympathetic switching · Stress resilience
Best For
Before climbing · During rests · Mental reset after failed attempts · Pre-crux calming · Fear management
Side-by-Side Comparison
| Test | Type | Primary Use | Pranaclimb Role | When to Use |
|---|---|---|---|---|
| 🔵 MBT | Dynamic / Movement | Performance CO₂ test | Primary RBA diagnostic | Pre-season, RBA, redpoint prep |
| 🟢 BOLT | Static / Resting | Baseline CO₂ health score | Daily efficiency tracker | Every morning, recovery days |
| 🟣 Huberman | Psychological | Stress + CO₂ control | Mental performance tool | Before climbing, between burns |
"In climbing, CO₂ is both signal and lever. Learn to read your breath — and you learn to read your limit."— Pranaclimb
The Pranaclimb Summary
- MBT — tests how well you tolerate breathlessness during movement → directly reflects crux performance and W′ depletion
- BOLT — your daily respiratory efficiency score → predicts lower BR, better recovery, calmer climbing
- Huberman — trains composure while CO₂ rises → reduces panic breathing, improves focus, stabilises BR↔RPE
🫁 The Pranaclimb MBT Scale (Climbing-Specific)
The cMBT (Climbing Maximal Breathlessness Test) gives you a direct readout of your CO₂ resilience on the wall. Here's how to interpret your score:
| cMBT (steps) | Zone | Interpretation | What This Means for Climbing |
|---|---|---|---|
| <25 | 🔴 Low | Poor tolerance | Early panic breathing, rapid BR spikes above CP |
| 25–40 | 🟠 Limited | Struggles above CP | Grey Zone feels chaotic, early fatigue |
| 40–60 | 🟡 Moderate | Functional | Holds CP briefly, fades late in route |
| 60–80 | 🟢 Good | Strong control | Better pacing & recovery between burns |
| 80+ | 🔵 Elite | Exceptional | Calm under pump, delayed RCP, redpoint resilience |
CO₂ Discard Rate & Exhale Duration
How long you can exhale is a window into your CO₂ tolerance and nervous system regulation. Here's how to interpret exhale duration in the field:
| Exhale Duration | CO₂ Tolerance Level | Breathwork Implications for Climbers |
|---|---|---|
| <15 sec | Low | Over-breathing, poor recovery, stress reactivity. Train slow exhales + breath holds. |
| 15–30 sec | Average | Functional but improvable. Use CO₂ retention drills and nasal-only breathing. |
| 30–60 sec | High | Supports endurance, composure, and efficient energy use. Maintain nasal dominance. |
| 65–120 sec | Optimal | Excellent nervous system regulation. Ideal for active recovery between attempts. |
🔬 The Science: Breath Holds, Valsalva & Forced Exhalation
A study published in The Journal of Applied Physiology presents the first evidence that well-trained climbers exhibit breath holding and Valsalva-like efforts during climbing movements — with intermittent mouth pressures averaging 31 ± 46 cmH₂O.
"Breath holding may serve an important function in supporting climbing-specific movements, particularly on overhanging wall inclines."— Journal of Applied Physiology
However, research also shows that forced exhalation outperforms the Valsalva manoeuvre for force production while minimising cardiovascular risk:
Indoor rock climbing evokes a substantial pressor response — high blood pressures that may exceed those seen during 40 other resistance exercises. This is why managing breath holds and exhalation timing is critical for both performance and safety.
🫁 Field Drills — MBT Warm-Up & Cyclic Sighing Reset
CO₂ Tolerance Drill (MBT Warm-Up Test)
When: After warm-up, before your first burn.
- Sit or stand relaxed
- Normal inhale → normal exhale (don't force it)
- Pinch nose, hold breath, start stopwatch
- Stop at the first definite urge to breathe — not maximum hold
- Record time as your CO₂ tolerance score
20–30s = moderate → average buffering
30s+ = high tolerance → better anaerobic resilience, calmer at cruxes
Stress Recovery Drill (Cyclic Sighing Reset)
When: At rests on the wall, or between redpoint attempts. Quick, discreet — can be done on a shake-out stance or while chalking up.
- Take a double inhale through the nose — one big inhale + a top-up sniff
- Long, slow exhale through the mouth until empty
- Repeat 1–3 times
"MBT = diagnostic (capacity). Cyclic sighing = intervention (recovery). Together they extend your battery life above CP."— Pranaclimb
Breathwork Training Exercises
🌬️ CO₂ Exposure Training
After a normal exhale, hold breath as long as possible. Gradually increase duration over time. Builds chemoreceptor tolerance.
📦 Box Breathing
Inhale 4s → Hold 4s → Exhale 4s → Hold 4s. Repeat 5–10 minutes. Balances nervous system before climbing.
💨 Slow Controlled Breathing
Extend exhale to twice the inhale length (e.g., 4s inhale, 8s exhale). Activates parasympathetic response.
👃 Nasal Breathing
Breathe through nose during daily activities, exercise, and sleep. Enhances CO₂ retention and nitric oxide production.
Aerobic Thresholds & Energetic Capacity in Climbing
V̇O₂peak, Critical Power (CP), and W′bal represent interconnected markers of aerobic performance. CP is typically 70–90% of V̇O₂peak depending on training status. W′bal quantifies the finite anaerobic energy reserve available once exercise exceeds CP — it depletes during high-intensity bursts and recovers below CP.
Pranaclimb models these dynamics non-invasively using BR, RPE, and HRR₆₀ to estimate CP and track W′bal depletion and recovery in real-time field settings — no lab required.