Sport Climbing
Precision over power.
Finger flexors are a different species of muscle — short, fatigue-resistant, catastrophically injury-prone when overloaded. FitX measures them the way strength scientists do in the lab, with the Critical Force model, not the rep-and-set thinking that belongs in a weight room.
What FitX brings to climbing.
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Critical Force Calculator
Enter one 10-second max-hang load and your bodyweight. Get your CF as a percentage of bodyweight, placed in Giles’s research-backed zones.
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Hangboard periodization
Three-week rotation across max-hang, repeaters, and no-hang grip work — the exact structure López-Rivera validated for continued finger-strength adaptation.
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CNS fatigue tracker
Logs grip-specific nervous-system load so you don’t climb a project the day after a heavy hangboard day. The app says no for you.
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Full CF Protocol (Elite)
A three-session guided test that fits the full hyperbolic curve to your data — not a one-point estimate. Research-grade finger-flexor benchmark.
The science in one paragraph.
Monod and Scherrer modelled muscle endurance as a hyperbolic Force–Time curve in 1965. Giles adapted the model to finger flexors in 2006. Above CF, you burn a finite anaerobic reserve (W′) until failure; below CF, you can hold forever. Every FitX climbing calculator derives from that curve.
Read the full methodologyCF progression across a 16-week training block — intermediate to advanced zone crossing at week 10.
Ready to climb with numbers?
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