Biomechanical comparison of pin and freeride ski mountaineering bindings in recreational skiers

Abstract

Previous studies on competitive ski mountaineering have shown that increasing equipment weight increases metabolic cost of the skier. However, whether differences in weight influence the kinematics or efficiency of uphill skinning in recreational skiers remains unknown. Therefore, the purpose of this study was to compare the lower body kinematics and mechanical efficiency of uphill skinning between these bindings in recreational skiers. Sixteen skiers skinned on a treadmill on matching skis with pin or freeride bindings, for three-minute stages at grades of 8% or 15% while kinematics and heart rate were recorded over the final thirty seconds. A walking graded exercise test was performed to estimate oxygen consumption and respiratory exchange ratio from heart rate during the skinning protocol, for calculation of aerobic metabolic rate. Sagittal plane joint angles of the lower limb and torso, cycle metrics, vertical power, aerobic metabolic rate, and mechanical efficiency were all compared for each condition parametric mapping or linear mixed effect models. Results showed that in the freeride binding, compared to the pin, there was slightly greater ankle plantarflexion (p=.05), knee flexion (p=.02), and hip flexion (p=.05) around toe-off. However, these differences were no more than 2° of joint motion, and isolated to a small area of the gait cycle. Differences in cycle metrics were also found between the bindings, with slower cycle rates (p<.001, d=0.34), longer cycle lengths (p<.001, d=0.36), cycle time (p<.001, d=0.36), and higher step heights (p<.001, d=0.32) in the freeride binding. While statistically significant, these differences were small in magnitude and effect size. Supporting that differences in kinematics were likely negligible, our results found no significant differences in vertical power (p=.69), aerobic metabolic rate (p=.61), or mechanical efficiency (p=.81) between bindings. Collectively our results show that in laboratory settings at the grades tested, there is no difference between a pin and freeride binding that are relevant for recreational skier uphill movement or efficiency.