The validity and utility of the all-out test for forearm flexor critical force

An all-out test has been created to measure critical force (CF) of the forearm flexor muscles, but its suitability for rock climbing is unclear. We recruited 26 participants (14 male; 12 female), to assess the reliability and validity of the all-out CF test. Using a hang board and force plate, participants completed (i) two 4-min all out tests on separate days and (i) four constant-force tests to the limit of tolerance on two additional days. CF was greater in the all-out protocol (122 [56] N) compared to the constant-force protocol (98 [43] N), with excellent consistency between the two protocols (ICC(3,1) = 0.93, p <  0.001). In contrast, W' was not different between protocols (p = 0.120), but there was only moderate absolute agreement (ICC(2,1) = 0.65, p < 0 .001) between protocols. For the repeated all-out tests, there was excellent test-retest reliability for CF (ICC = 0.97, p <  0.001) and W' (ICC = 0.97, p <  0 .001). CF derived from the constant-force (rho = 0.60, p = 0.044) protocol was related to self-reported International Rock Climbing Research Association redpoint score from the previous 12 months, whereas the all-out CF (rho = 0.59, p = 0.05) and both measures of W' were not (p > 0.05). While potentially useful for tracking changes in forearm flexor performance, the all-out test does not accurately measure the highest sustainable intensity these muscles can perform, and it likely unsuitable for exercise prescription, limiting its utility in rock climbing.