G-Tox shakeout for 9x better recovery than standard shaking (sharing my research notes)
Intro:
I'm currently researching this for a blog post, but since it's getting basically zero traffic, figured I'd share the findings here where people might actually find them useful.
Most of us shake our arms out wrong and rest too little between attempts. Here's what the actual research says.
1. Lactic acid doesn't cause the pump
Common myth. Lactate is actually used as an energy substrate, not a waste product. The real cause: when your forearm muscles contract hard, they compress the blood vessels running through them. Above ~70% max voluntary contraction, vessels are nearly fully occluded — you're working anaerobically, with no fresh oxygen in and no waste out. That's the pump. Recovery = restoring blood flow, nothing else.
2. G-Tox: a 9x improvement from one change
In 2005, a researcher at the University of Chichester (Luke Roberts) tested the standard dangling-arm shakeout against a technique developed by Eric Hörst called G-Tox.
Setup: climbers did a hard traverse, then got a 2-minute recovery window using either method. Grip strength was measured after.
- Standard dangling shakeout: +2% grip strength recovered
- G-Tox: +18% grip strength recovered
Same 2 minutes. 9x difference from a positional change.
The protocol is stupidly simple:
- Raise one arm overhead, shake loosely for 5 sec
- Drop the same arm to your side, shake loosely for 5 sec
- Switch arms, repeat
Why it works: gravity assists venous return. When your arm hangs down, blood pools in the hand/forearm. Raising it overhead helps pull that blood (and the metabolic waste) back toward the heart. Alternating creates a pumping effect.
3. Flash pump — warm-up isn't optional
Climbing hard before your forearms are properly warmed up causes a specific, disproportionately bad pump that takes way longer to clear. Cold muscle has reduced vasodilatory capacity, so even moderate effort pushes you into near-occlusion. A gradual pyramidal warm-up (easy → moderate → sub-limit) before projecting is the difference between 2 quality attempts and 5.
4. You're probably not resting long enough
Steve Bechtel / Juliet Hammer's work:rest framework, based on climbing type:
- Sub-limit boulder problems: 1:8 ratio (10s attempt → ~80s rest)
- Limit boulder problems: 1:20 ratio (5s attempt → ~100s rest, or ~1 min/move)
- Power endurance: 1:6 to 1:8 (5 min on wall → 30+ min rest)
- Endurance/sport routes: 1:4 (7 min route → ~28 min rest)
Notice limit bouldering needs MORE relative rest than endurance climbing, not less — because it hammers your CNS, not just your forearms.
5. Local fatigue vs CNS fatigue — the one that actually kills sessions
- Local fatigue (the pump): clears in 5-15 min with proper rest + G-Tox
- CNS fatigue (from max-intensity efforts — limit moves, campus boarding, heavy hangs): can persist 24-48 hours
Your forearms can feel completely fine while your power output is still down ~30%. You won't notice until you're actually on the wall. This is why sessions fall apart after the 3rd attempt even when you "feel fine" — and why going back on the board the day after a max session is often a bad idea, even though your arms don't feel pumped anymore.
A 2024 study on elite climbers post-competition found forearm swelling took a full 12 hours to return to baseline — not 20 minutes, not 2 hours.
TL;DR
- Switch to G-Tox — free, 30 seconds to learn, +18% vs +2% recovery
- Rest longer than feels necessary, especially after limit efforts (local fatigue clearing ≠ CNS recovery)
- Never skip warm-up on performance days
Happy to share sources if anyone wants to dig into the studies themselves.
