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Preloading of the thrust phase in cross-country skiing
International Journal of Sports Medicine
|March 1, 1987
Summary
This study investigated the stretch-shortening cycle in elite cross-country skiers using advanced techniques. Results show this cycle is integral to the leg kick and arm thrust phases, crucial for efficient skiing performance.
Area of Science:
- Biomechanics
- Exercise Physiology
- Sports Science
Background:
- The stretch-shortening cycle (SSC) is a fundamental mechanism in human movement.
- Its application in dynamic sports like cross-country skiing requires detailed biomechanical analysis.
Purpose of the Study:
- To investigate the occurrence and characteristics of the stretch-shortening cycle during the diagonal technique in cross-country skiing.
- To analyze the muscle activation patterns and joint kinematics associated with the SSC in elite skiers.
Main Methods:
- Utilized cinematographic, force platform, and telemetered electromyography (EMG) techniques.
- Measurements were taken from elite international cross-country skiers during competition and specialized outdoor tests.
- Analysis included fixed and variable uphill courses with varying gradients (2.5-11 degrees).
Main Results:
- Identified distinct unweighting, braking, and propulsion phases preceding the leg kick.
- Angular velocity curves indicated segmental SSC occurrence in hip, knee, and ankle joints.
- Similar SSC phenomena were observed in the elbow joint during pole plant and thrust phases.
- On steep uphills, muscle activation and ground reaction forces mimicked slow level running.
Conclusions:
- The stretch-shortening cycle is a key component of the diagonal cross-country skiing technique.
- A sequential, joint-to-joint model of preloading for the leg thrust phase was proposed.
- Understanding the SSC can inform training and technique optimization for cross-country skiers.