Finger flexor strength and the effect of acute handgrip fatigue in advanced level boulderers

Bouldering is a discipline of rock climbing that involves short (~4m-high) typically overhanging problems without ropes. Bouldering places a high demand on the finger flexors and consists of ~8s isometric holds across 30-40s climbing problems, with ~115s rest between attempts (White and Olsen, 2010, Journal of Strength and Conditioning Research, 24, 1356–1360). Strength and endurance of the fingers appear to discriminate rock climbing ability (Marcolin et al. 2022, Journal of Strength and Conditioning Research, 36, 1099-1104), however this has not been tested in boulderers or outside a laboratory setting. The aim of this study was to investigate if climbing specific finger strength relates to ability in advanced boulderers, and to assess the effects of acute fatigue and recovery. With institutional ethical approval, 13 advanced boulderers (12 males, 1 female; age 22±3 years; height 172.5±8.2cm; mass 65.8±5.3kg; International Rock Climbing Research Association (IRCRA) scale 19-22) volunteered. At baseline, dominant arm finger flexion strength was measured using an open-hand crimp hold on a 20mm edge. Participants performed the test in a seated, cross-legged position on the floor (with a weighted vest if required) with the dynamometer height adjusted on an individual basis so that the arm was positioned directly above the head with no elbow flexion observed. Peak force was recorded at 80Hz using a climbing specific Tindeq Progressor 300 dynamometer (Trondheim, Norway), and reported in Newtons/ body mass (N.kg^-1). Participants climbed a circuit on a training wall, and repeated until failure due to fatigue. Immediately after failure, participants repeated the open-hand crimp strength test. The strength test was repeated every 2 minutes until 20 minutes. At baseline, the peak force for the open hand crimp was 7.86±1.40 N.kg^-1 and was significantly correlated with self-reported climbing grade (r=0.810, P <0.001). Peak force was significantly reduced immediately after the fatiguing protocol (6.24±1.03 N.kg^-1; P <0.001) and remained significantly reduced at both 10 (6.73±0.95 N.kg^-1; P <0.001) and 20 min (7.05±1.29 N.kg^-1; P <0.001). However, the gradient of recovery for the first 10-minutes was steeper for the higher ability boulderers (IRCRA 22, m=0.059) than those graded IRCRA 21 (m=0.046) and 19-20 (m=0.038). The results indicate that boulderers climbing at higher grades demonstrate higher finger flexor strength and recover from a fatiguing effort at a faster rate. In addition, 2-minute rest periods between force measurements appears to impact force generation recovery, suggesting that advanced boulderers typically require longer rest between bouldering attempts.