A biomechanical field testing approach in snow sports: Case studies toward a detailed analysis of joint loading

Abstract

In this study, kinematic and kinetic measurements were combined to assess the effects of removing the stiff shaft from a ski boot. It was hypothesized that joint flexion at the ankle, knee and hip increase and reduce joint loading specifically at the knee. A previously developed force sensor was combined with a high-speed camera system for data collection of 6 degrees of freedom ground reaction forces and three-dimensional marker data in the field on a wave slope. The collected data were used as input to a musculoskeletal model for the estimation of joint kinematics and joint moments and contact forces in the ankle and knee. The force sensor, which was previously used for skiing, had experienced wear and tear and was thus prone to breakage. As a result, joint loading could only be analyzed for two skiers. These two skiers did not use the added range of ankle flexion to its full extent, but showed substantial reductions in joint moments and joint contact forces (e.g. knee compression force from 85 to 57 N/kg). Only one of the five experienced skiers tested was able to adopt the anticipated movement pattern by substantially increased maximum ankle joint flexion angle (from 10° to 37°) and knee joint flexion angle (from 93° to 105°) and the respective ranges of motion when skiing through a wave course. The study provides information on possible individual adaptations to ski boot modifications. The mechanical construction of the force sensor will need to be modified to withstand the high forces expected during freestyle skiing. The study also supports the future use of this measurement setup for comprehensive studies in snow sports, provided that a sufficient training period is given.

Application of Inertial Motion Unit-Based Kinematics to Assess the Effect of Boot Modifications on Ski Jump Landings—A Methodological Study

“…In order to gain a noticeably greater ankle flexion, only two screws per boot were used to fix the shaft at the medial and lateral connection point. To ensure the durability of the plastic around the pivot points and to prevent breakages, small aluminum plates were manufactured to reinforce the joint on the inside and outside of the shaft [19].…”

Biomechanical Analysis of Arm Manipulation in Tai Chi

“…In the competitive Taijiquan competition, they all appear in the form of combination, so the actions tested in this study are reflected in the form of combination. e arm manipulation of competitive Taijiquan can be divided into: take the shoulder joint as the axis, lift the arm in a certain direction and stop at a certain position, and the range of motion is no more than 180 ° [16,17]. Flexion and extension: the upper arm is fixed and the elbow joint is the axis.…”