Work-relief ratios and imbalances of load application in sport climbing: another link to overuse-induced injuries?

An imbalanced load application of the upper extremity may contribute to overuse-induced injuries of the fingers. Thus, the present study evaluated load-application symmetry between the right and the left hand and its work-relief ratios (WRR) depending on climbing ability and pre-exhaustion level. Twenty-eight sport climbers (age: 29 ± 8 years; body mass index: 22 ± 2 kg/m(2); years of climbing: 10 ± 6; climbing level: 6+ UIAA to 9 UIAA) were assigned to a group of recreational (≤8-UIAA, n = 14) or a group of ambitious (≥8 UIAA, n = 14) climbers. Blood lactate and perceived exertion level were recorded at the end of the climbing attempt. Load application and WRR were derived from video analysis separately for the left and the right hand. Differences in load-application time between the left (47 ± 4%) and the right (53 ± 4%) hand (P < 0.001) were observed. Irrespective of side differences, the overall WRR was 5:1. Increasing climbing level leads to a more symmetric load application (r = -0.42, P < 0.03). Differences of lactate concentration and exertion level were found between the pre- and the non-pre-exhausted group. Depending on climbing ability and exhaustion level, load application for the dominant hand (right) prevails. Further longitudinal studies should focus on imbalanced load application and overuse-induced climbing injuries.