Imitation jumps in ski jumping: Technical execution and relationship to performance level

ABSTRACT Imitation jumps are frequently used in training for ski jumping. Yet, the dynamics of these jumps differ considerably. Thus, the relevance of imitation jumps for ski jumping performance is not elucidated. The aim of this study was to investigate the relationship between the technical execution of imitation jumps and ski jumping performance level. We compared the imitation jumps of 11 ski jumpers of different performance levels using a Spearman correlation transform of time traces of the kinetics (measured using force cells and motion capture) of imitation jumps. The kinetic aspects that were related to performance centred on the moment arm of ground reaction force to the centre of mass before the onset of the push-off, angular momentum early in push-off, thigh angle during the main period of push-off and vertical velocity towards the end of push-off. We propose that the thigh angle may be a key element allowing high development of linear momentum while preparing for appropriate aerodynamic position. Furthermore, the findings suggest that the kinetic development prior to (and during) push-off is more important than the kinematic end state at take-off.

[1]  F Beaumont,et al.  Numerical investigation of the early flight phase in ski-jumping. , 2017, Journal of biomechanics.

[2]  S. Lorenzetti,et al.  Conditioning exercises in ski jumping: biomechanical relationship of squat jumps, imitation jumps, and hill jumps , 2019, Sports biomechanics.

[3]  Z. Svoboda,et al.  Kinematic Analysis of the Take-Off and Start of the Early Flight Phase on a Large Hill (HS-134 m) during the 2009 Nordic World Ski Championships , 2011 .

[4]  Milan Elfmark,et al.  Analysis of the beginning of the early flight phase of the ski jump in athletes with different performance levels , 2011 .

[5]  Hermann Schwameder,et al.  Biomechanics research in ski jumping, 1991–2006 , 2008, Sports biomechanics.

[6]  P. Leva.  Adjustments to Zatsiorsky-Seluyanov's segment inertia parameters. , 1996 .

[7]  Melanie Keller,et al.  Kinematics and Kinetics of Squats, Drop Jumps and Imitation Jumps of Ski Jumpers , 2016, Journal of strength and conditioning research.

[8]  Mikko Virmavirta,et al.  Techniques Used by Olympic Ski Jumpers in the Transition From Takeoff to Early Flight , 1995 .

[9]  Simon M. Luethi,et al.  Methodological Problems in Optimization of the Flight Phase in Ski Jumping , 1987 .

[10]  Milan Elfmark,et al.  Kinematic Chains in Ski Jumping In-run Posture , 2013, Journal of human kinetics.

[11]  M. Bobbert,et al.  How do elite ski jumpers handle the dynamic conditions in imitation jumps? , 2016, Journal of sports sciences.

[12]  Mikko Virmavirta,et al.  Measurement of take‐off forces in ski jumping , 1993 .

[13]  H. Schwameder,et al.  Influence of body segment parameter estimation on calculated ground reaction forces in highly dynamic movements. , 2019, Journal of biomechanics.

[14]  Mikko Virmavirta,et al.  Take-off analysis of the Olympic ski jumping competition (HS-106m). , 2009, Journal of biomechanics.

[15]  Body movement instructions facilitate synergy level motor learning, retention and transfer , 2012, Neuroscience Letters.

[16]  Ihor Zanevskyy,et al.  Dependence of ski jump length on the skier's body pose at the beginning of take-off. , 2010, Acta of bioengineering and biomechanics.

[17]  Keizo Yamamoto,et al.  Effect of posture on the aerodynamic characteristics during take-off in ski jumping. , 2016, Journal of biomechanics.

[18]  M Virmavirta,et al.  Take-off aerodynamics in ski jumping. , 2001, Journal of biomechanics.

[19]  Frantisek Vaverka,et al.  Kinematic characteristics of the ski jump inrun: a 10-year longitudinal study. , 2010, Journal of applied biomechanics.