Force control during fatiguing contractions in elite rock climbers

Abstract

The differences between rock climbers and controls in finger flexor (FF) muscles’ motor control were determined in 11 climbers and 10 sedentary participants. Maximal voluntary contraction (MVC) was assessed and after 5 min of rest an isometric contraction at 80% MVC was performed until exhaustion. During contraction, the force signal was recorded, from which the variation coefficient (VC) was then calculated as an index of force control accuracy. Climbers showed significantly higher MVC (+46%, p<0.05) and MVC per unit of muscle-plus-bone area (MVC/MBA; +13%, p<0.05). Endurance time at 80% MVC was 43% longer in climbers than in controls (33±4 vs. 23±5 s, respectively; p<0.05). VC throughout the first 20 s of contraction was significantly lower in climbers than in controls (p<0.05). Maximum force results and force signal analysis during constant-load contraction at 80% MVC revealed significant differences in muscle characteristics and motor control between the two groups. In particular, climbers showed stronger and more efficient FF muscles, which were capable of sustaining the requested effort (80% MVC up to exhaustion) for a longer period of time and with a steadier force output. These results suggest a shift of climbers’ muscles toward faster and more resistant motor units due to years of high-intensity isometric contractions typical of this physical activity.