What Actually Happens When You Scream
Research by Aliverti et al. revealed something important about forceful vocalisations during exercise. During normal exercise, the expired volume is almost entirely abdominal — driven by the diaphragm and abdominal muscles working together. But during phonation — yelling, grunting, screaming — all three chest-wall compartments contribute: the abdomen, the rib cage, and the upper chest.
This matters enormously for climbers. It means that every scream or grunt shifts your breathing mechanics away from the efficient, diaphragm-driven pattern and recruits accessory muscles that are already under load from stabilising your body on the wall.
The Three-Compartment Problem
Think of your breathing system as having three compartments: the abdomen (most efficient, driven by the diaphragm), the rib cage (moderate cost, intercostal muscles), and the upper chest (highest cost, accessory muscles — scalenes, sternocleidomastoid, upper trapezius).
Efficient breathing uses compartment one almost exclusively. When you scream, all three light up simultaneously. The thoracic and abdominal pressures shift. The pattern that was working in your favour gets disrupted. And as Dempsey et al. proposed, the respiratory system's own control can contribute to exercise limitation through complex respiratory-cardiac interactions — meaning that breathing mechanics that go wrong have consequences beyond just ventilation.
"Forceful yelling may exert a considerable effect on thoracic and abdominal pressure as well as cause capacity changes that affect ventilation effectiveness during extreme exercise."Aliverti et al.
But Screaming Also Works — Sometimes
This isn't a case against screaming. It's a case for understanding when it helps and when it costs. Ohya et al. (2015) found that yelling increases ventilation and performance output in maximal efforts. Chen et al. (2021) showed that yelling boosts VO₂, O₂ pulse, and ventilatory efficiency through enhanced neural drive. For a single explosive move — a dyno, a deadpoint, a desperate lock-off — a well-timed power exhale or shout can genuinely enhance force production.
The problem arrives when screaming becomes a habit rather than a tool. Satoh et al. (2023) found that repeated forceful vocalisations can overload the diaphragm, creating strain risk. And in the Pranaclimb framework, each scream adds approximately +5 BPM to your Effective Breathing Rate — meaning ten screams in a minute pushes your Effective BR deep into the severe domain regardless of what your raw breath count says.
The Effective Breathing Rate Model
This is why Pranaclimb uses Effective BR rather than raw breath count. Raw BR misses the hidden cost of expression. A climber who takes 40 breaths per minute but screams six times has an Effective BR of 70+ — well into the severe domain — despite what the raw number suggests.
| Expression | Δ BR Adjustment | Threshold |
|---|---|---|
| Grunt / Passat | +3 BPM each | Useful in small doses |
| Scream / Yell | +5 BPM each | 1–3 = enhancer; 4+ = limiter |
| Breath hold (<1s) | +2 BPM | Tactical on cruxes |
| Breath hold (>4s) | +10 BPM | Avoid — accelerates fatigue |
| Sigh (relief) | 0 to −1 BPM | Recovery signal — use at rests |
The Practical Rule
One precise power exhale at the hardest move of a crux sequence — timed, controlled, complete. That's the target. Not ten screams scattered across a route. Not a shout at every hard clip. Budget your expressive breathing the way you budget your anaerobic reserve — because physiologically, they are the same thing.
The climbers who seem to stay calmest at their limit aren't suppressing expression. They're directing it. One breath, one move, maximum effect.