Finger flexors fatigue in trained rock climbers and untrained sedentary subjects

The present series of experiments were conducted to access the surface EMG frequency parameters during repeated fingertip isometric contractions to determine if they can be used as a fatigue index under specific grip used in rock climbing. Electromyograms of the finger flexors and extensors were characterised in ten elite climbers and ten non-climbers. The exercise consisted in reaching 80 % of maximal isometric finger force as quickly as possible intermittently with a 5-s contraction followed by 5-s of rest until exhaustion (i. e. when the subject was unable to maintain 80 - 70 % MVC force range for the 5 s). The results clearly indicate that expert climbers performed significantly greater fingertip force than sedentary subjects (420 +/- 46 N vs. 342 +/- 56 N). This force was maintained during twelve repetitions (12.88 +/- 4.96) in sedentary subjects, whereas the climbers maintained the force during nineteen repetitions (19.33 +/- 4.84). The median frequency of both the flexor and extensor EMG power spectra decreased during fatiguing isometric contractions, but at different rates in climbers and non-climbers. In non-climbers, the results replicated previous findings, whereas in climbers the results were novel.