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

Abstract

The take-off is often considered the most significant and difficult phase of a ski jump. Thus, the purpose of this study

The "Akopian" vault performed by elite male gymnasts: Which biomechanical variables are related to a judge's score?

“…Reliability based on repeat digitization of a sample sequence was < 1 % for temporal and spatial parameters and < 4.5 % for velocity parameters. The data were manually digitized by an experienced researcher (Janura, Cabell, Svoboda, Elfmark, & Zahálka, 2011).…”

Kinematic Structure at the Early Flight Position in Ski Jumping

“…Factor weights of the manifest variables in this factor were high and nearly homogeneous. A smaller body chord angle relative to the horizontal axis during the early flight supports a more effective aerodynamic position in the early phase of flying (Janura et al, 2011; Müller et al, 1996). …”

“…This allows for better aerodynamic efficiency (minimising the drag force in the leg). The minimum value of the angle is subject to the favourable position of the lower leg during the take-off in the contact take-off phase (Janura, 2011). Jumpers who placed their lower leg more in the anterior position could more efficiently carry out a rotation of the body at the take-off (common centre of gravity moved forward more quickly).…”

“…In many studies, the correlation coefficients between the biomechanical parameters describing the take-off and the length of jump occurred mainly in the interval r=0.40–0.60 (Vaverka et al, 1997). Some studies reported the importance of the optimal aerodynamic positions of the ski jumpers in the early flight phase (Janura et al, 2011; Jošt, 2010; Jošt et al, 1998; Schmölzer and Müller, 2005; Virmavirta et al, 2001; 2009; Vodičar and Jošt, 2011). The correlation between body angle and horizontal axis proved to be most significant (Virmavirta et al, 2005).…”

“…The best ski jumpers can perform early flight technique optimally in the most difficult conditions. In practice, we can find major differences in the quality of ski jumpers (Janura et al, 2011). The quality of early flight technique is determined in all repetitions by the same mechanical factors.…”