Change in finger force production and muscle activation in the forearms of rock climbers during treadwall climbing

Abstract

Rock climbing is a multi-faceted sport requiring finger flexor strength and endurance. Sustained isometric contractions lead to the build-up of metabolic byproducts that fatigue the finger flexors, however the effect of climbing ability on muscular fatigue is not fully understood. The purpose of the present study is to investigate the effects of rock climbing ability on time to fatigue (TTF), relative finger force production (REL FP), change in FP (DeltaFP), and changes in muscle activity during bouts of climbing on a treadwall. Eight advanced (6 male, 2 female: 29.3 + or = 4.7 yrs, 69.1 + or = 6.9 kg, years experience: 11.1 + or = 5.2) and seven novice (5 male, 2 female: 21 + or = 2.3 yrs, 67.6 + or = 3.8 kg, years experience: 3.0 + or = 2.6) subjects participated. Subjects warmed-up on the treadwall and mounted force tranducer. Electromyographic (EMG) electrodes were placed over the flexor digitorum superficialis (FDS), biceps brachii and triceps brachii muscle to measure motor unit action potentials. Root mean square (RMS) and median frequency (MF) were analyzed from EMG data. Subjects performed a pre-exercise, 20-second maximal voluntary isometric contraction (MVIC PRE) with the fingertips of the dominant hand (DH) and non- dominant hand (NDH). The climbing protocol consisted of climbing for 5-minute intervals. Subjects performed another MVIC after each interval. EMG and force data were recorded during MVICs. A total of six intervals were performed, or until failure. Group comparisons were made at the 5th interval (MVIC POST). Climbing ability and handedness were analyzed using a 2x2 mixed ANOVA with repeated measures (alpha level < 0.05). Significant group differences were observed for TTF, REL FP, and percent DeltaFP and FDS DeltaMF. Advanced climbers' average REL FP during MVIC PRE was 5.6 + or = 1.4 N/kg BW and 5.2 + or = 1.6 N/kg from the DH and NDH, respectively. Novice REL FP was 3.1 + or = 0.8 N/kg BW and 3.1 + or = 1.0 N/kg. Novices DeltaFP decreased 30.8 + or = 16.0% and 24.9 + or = 18.6%, advanced climbers experienced no change. Advanced MF increased 4.8 + or = 25.9% and 7.7 + or = 18.8%, novice MF decreased 22.7 + or = 6.5% and 12.6 + or = 15.5%. In conclusion, advanced climbers demonstrated a resistance to climbing-specific fatigue during bouts of treadwall climbing.