Bojan Jost

The Factor Structure of Chosen Kinematic Characteristics of Take-Off in Ski Jumping

The Factor Structure of Chosen Kinematic Characteristics of Take-Off in Ski Jumping With a sample of 29 of the best Slovenian ski jumpers, a research project was carried out with the purpose of determining the structure relation of chosen dynamic and kinematic variables during the take-off of ski jumpers. The experiment was performed in August 2008 on the jumping hill in Hinterzarten, Germany (K=95m). The subjects jumped seven times without breaks between rounds. The analysis was done on variables that determine the technique of take-off in ski jumping (in-run velocity - km/h, vertical take-off velocity - m/s, precision of take-off - cm). The criteria variable was the length of the jump (m). The variability of the long distance of the jumps was significantly strong. The reliability of all used multi-item variables was high and satisfactory in most variables (in-run velocity - 0.98, vertical take-off velocity - 0.98, precision of take-off - 0.85, length of the jump - 0.95). The factor analysis produced an independent latent structure (explanation of variance = 93.3%) of five specific factors (1. in-run velocity connected to distance jumped (39.8 % of VAR.), 2. vertical take-off velocity strongly connected to distance jumped (26.0 % of VAR.), 3. precision of take-off partly connected to distance jumped (14.9 % of VAR.), 4. precision of take-off in the 7th round (6.7 % of VAR.), 5. precision at take-off in the 4th round (5.7 % of VAR.). The present factor structure confirms the hypothetical model of three independent motor tasks to be optimally realized in the take-off of the ski jumper. Criteria variables influencing the length of jumps were mainly associated with the first two factors, which confirm the basic hypothesis that the length of the jump reflects the overall output quality of the first two factors. The accurancy factor of take-off affects the length of the jumps indirectly and latently through these two fundamental factors.

Kinematic Structure at the Early Flight Position in Ski Jumping

The purpose of our research was to establish the variability of correlation between the length of the jumps and selected multi-item kinematic variables (n=9) in the early flight phase technique of ski jumping. This study was conducted on a sample of elite Slovenian ski jumpers (N=29) who participated in the experiment on a jumping hill in Hinterzarten, Germany (HS95m) on the 20th of August, 2008. The highest and most significant correlations (p=0.01) with the length of the ski jump were found in the multi-item variable height of flying, which was also expressed with the highest level of stability of the explained total variance (TV) on the first factor (TV=69.13%). The most important characteristic of the aerodynamic aspect of early flight was the variable angle between the body chord and the horizontal axis with significantly high correlations (p<0.05). The stability of that aerodynamic factor was very high (TV=65.04%). The results were essentially similar for the multi-item variable angle between left leg and the horizontal axis (TV=61.88%). The rest of the multi-item kinematic variables did not have significant correlations with the multi-item variable length of jump. Only two more variables, the angle between the upper body and the horizontal plane (TV=53.69%), and the angle between left ski and left leg (TV=50.13%), had an explained common variance on the first factor greater than 50% of total variance. The results indicated that some kinematic parameters of ski jumping early flight technique were more important for success considering the length of the jump.