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J Strength Cond Res. 2016 Mar;30(3):643-52. doi: 10.1519/JSC.0000000000001166.

Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers.

Author information

1
1Institute for Biomechanics, Swiss Federal Institute of Technology in Zurich (ETHZ), Zurich, Switzerland; 2Department for Sport, Movement and Health, University Basel, Basel, Switzerland; 3Swiss Ski, Haus des Skisportes, Bern, Switzerland; and 4Swiss Federal Institute of Sports, Magglingen, Switzerland.

Abstract

Squats, drop jumps, and imitation jumps are commonly used training exercises in ski jumping to enhance maximum force, explosive force, and sport-specific skills. The purpose of this study was to evaluate the kinetics and kinematics of training exercises in ski jumping and to find objective parameters in training exercises that most correlate with the competition performance of ski jumpers. To this end, barbell squats, drop jumps, and imitation jumps were measured in a laboratory environment for 10 elite ski jumpers. Force and motion data were captured, and the influence of maximum vertical force, force difference, vertical take-off velocity, knee moments, knee joint power, and a knee valgus/varus index was evaluated and correlated with their season jump performance. The results indicate that, especially for the imitation jumps, a good correlation exists between the vertical take-off velocity and the personal jump performance on the hill (R = 0.718). Importantly, however, the more the athletes tended toward a valgus knee alignment during the measured movements, the worse their performance (R = 0.729 imitation jumps; R = 0.685 squats). Although an evaluation of the athletes' lower limb alignment during competitive jumping on the hill is still required, these preliminary data suggest that performance training should additionally concentrate on improving knee alignment to increase ski jumping performance.

PMID:
26418370
PMCID:
PMC4780482
DOI:
10.1519/JSC.0000000000001166
[Indexed for MEDLINE]
Free PMC Article

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