Effect of simulated rock climbing finger postures on force sharing among the fingers

Objective. To study the forces applied by each finger in different joint postures simulating rock climbing gripping postures. Design. Subjects in sitting posture applied fingertip forces perpendicular to horizontal force sensors in three different finger postures. Background. Data provided by the literature indicate that middle and ring finger are commonly injured. However, no quantitative assessment of the forces applied by each finger related to the joint postures has been made. Methods. Six elite rock climbers performed finger flexion in a single-finger task and a four-finger task. The tests were conducted in an extended posture, a curved posture (the joints belonging to the finger were flexed) and an intermediate posture (the joints were flexed, except the distal one which was fully extended). Each fingertip force was expressed in absolute value and in percentage of the maximal force capacity of the finger. Results. The greater force was applied by the middle finger (20.8 N), whatever the posture. The relative involvement amounted to 105% for the ring finger in the curved posture. Conclusions. The great force applied by the middle finger and the great relative involvement of the ring finger in the curved posture seem to be the main factors of injuries of these fingers.