The determination of finger flexor critical force in rock climbers

Purpose: To determine if the mathematical model used for the estimation of critical force (CF) and the energy store component W’ is applicable to intermittent isometric muscle actions of the finger flexors of rock climbers, using a multi-session test. As a secondary aim, the agreement of estimates of CF and W’ from a single-session test were also determined. The CF was defined as the slope coefficient and W’ the intercept of the linear relationship between total “isometric work” (Wlim) and time to exhaustion (Tlim). Methods: Subjects performed three (separated by either 20 m or >24 h) tests to failure using intermittent isometric finger flexor contractions at 45, 60 and 80% of their maximum voluntary contraction (MVC). Results: Force plotted against Tlim displayed a hyperbolic relationship, correlation coefficients of the parameter estimates from the work–time CF model were consistently very high (R2 > 0.94). Climbers mean CF was 425.7 ± 82.8 N (41.0 ± 6.2% MVC) and W’ 30882 ± 11820 N·s. Good agreement was found between the single and multi-session protocol for CF (ICC(3,1) = 0.900, 95% Confidence Interval [CI95%] 0.616 – 0.979), but not for W’ (ICC(3,1) = 0.768, CI95% 0.190 – 0.949). Conclusions: The results demonstrated the sensitivity of a simple test for the determination of CF and W’, using equipment readily available in most climbing gyms. While further work is still necessary, the test of CF described is of value for understanding exercise tolerance and determine optimal training prescription to monitor improvements the performance of the finger flexors.