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Dynamics of the in-run in ski jumping: a simulation study
Gertjan J C Ettema1, Steinar Bråten, Maarten F Bobbert
1Human Movement of Sciences Program, Faculty of Social Sciences and Technology Management, Norwegian University of Science and Technology, Trondheim, Norway.
Journal of Applied Biomechanics
|November 2, 2005
Summary
Ski jumpers face significant mechanical demands during the in-run due to environmental forces. Maintaining an aerodynamic position requires dynamic adjustments to counteract moments and manage forces on the feet and knees.
Area of Science:
- Biomechanics
- Sports Science
- Aerodynamics
Background:
- Ski jumping in-run requires maintaining an aerodynamic posture amidst dynamic environmental forces.
- Understanding the mechanical stresses on athletes is crucial for performance and injury prevention.
Purpose of the Study:
- To analyze the mechanical demands experienced by a ski jumper during the in-run phase.
- To investigate the forces and moments acting on the body in a static in-run position.
Main Methods:
- A 4-segment forward dynamic model (foot, leg, thigh, upper body) was utilized for simulation.
- Kinematic constraints of the curved in-run path were applied.
- Aerodynamic drag, lift, and snow friction forces were incorporated into the model.
Main Results:
- Forward rotating moments from drag and friction necessitated counteracting plantar flexion moments.
- The normal force on the foot increased from 0.88 G to 1.65 G from the straight to the curve.
- Increased knee joint moments were observed due to shifts in the center of pressure, indicating high angular acceleration during transitions.
Conclusions:
- The simulated static position requires unrealistically high rates of moment change.
- Athletes must dynamically alter their body configuration to reduce these moment rate demands.
- Dynamic adjustments are essential for managing mechanical loads during ski jumping in-runs.