Limited data exists on knee biomechanics in alpine ski turns despite the high rate of injuries associated with this maneuver. The purpose of the current study was to compare knee joint loading between a carved and a skidded ski turn and between the inner and outer leg. Kinetic data were collected using Kistler mobile force plates. Kinematic data were collected with five synchronized, panning, tilting, and zooming cameras. Inertial properties of the segments were calculated using an extended version of the Yeadon model. Knee joint forces and moments were calculated using inverse dynamics analysis. The obtained results indicate that knee joint loading in carving is not consistently greater than knee joint loading in skidding. In addition, knee joint loading at the outer leg is not always greater than at the inner leg. Differentiation is required between forces and moments, the direction of the forces and moments, and the phase of the turn that is considered. Even though the authors believe that the analyzed turns are representative, results have to be interpreted with caution due to the small sample size.
Miriam Klous, Erich Müller and Hermann Schwameder
Herbert Wagner, Michael Buchecker, Serge P. von Duvillard and Erich Müller
The aims of the present study were: (1) to compare the differences in the ball release speed and throwing accuracy between the ABOVE and SIDE throw; (2) to analyze kinematic differences of these two throwing techniques; and (3) to give practical applications to team handball coaches and players.
Ball release speed, throwing accuracy, and kinematics were measured via the Vicon MX 13 (Vicon Peak, Oxford, UK) from 12 male elite right-handed team handball players.
Results of our study suggest that the two throwing techniques differ significantly (P < .0073) in the angles and/or angular velocities of the trunk (flexion, left tilt and rotation) and shoulder (flexion and abduction) of the throwing arm that result in a significantly different ball release speed (1.4 ± 0.8 m/s; P < .001) and that throwing accuracy was not significantly different.
Our results indicated that the different position of the hand at ball release of the ABOVE and SIDE throws is primarily caused by different trunk flexion and tilt angles that lead to differences in ball release speed but not in throwing accuracy, and that the participants try to move their throwing arm similarly in both throwing techniques.
Roger Bartlett, Erich Müller, Christian Raschner, Stefan Lindinger and Caroline Jordan
The aim of this study was to compare the plantar pressures and forces recorded from both feet of two groups of javelin throwers of different performance levels, in order to investigate differences between skill levels. The study was carried out using an EMED insole system on a Tartan javelin runway at the University of Innsbruck, Austria. Most of the differences (at p < .01) between the two groups were found in the two foot contacts during the delivery stride. Higher maximum total forces (forces on the whole foot) and maximum pressures were recorded for the more skilled or club throwers during the right foot contact at the beginning of this stride. For the left foot landing before release, the club throwers exhibited higher overall maximum forces and overall pressures (the largest forces and pressures recorded on any of the different foot regions) than the novices. The differences between the groups in the medial forefoot region contributed significantly to this result.
Roger Bartlett, Erich Müller, Stefan Lindinger, Fritz Brunner and Calvin Morriss
This study compared three-dimensional release parameters and important features of the throwing technique for male javelin throwers of three different skill levels (elite, club, novice), recorded using three-dimensional cine or video. As expected, significant differences (p < .01) in throw distances and release speeds were found between all three groups. The only other release parameter for which a significant difference was found (between club and novice groups) was the yaw angle. The increase in release speed with increasing skill across the groups may be attributable in part to greater run-up speeds. Also important were significantly greater peak speeds of the throwing shoulder, elbow, and hand during the delivery stride for the elite group compared to the other groups. Significantly longer acceleration paths at the start of the delivery stride and a delay in elbow flexion until after final foot strike for the elite throwers were also important in generating greater release speeds.
Michael Buchecker, Stefan Wegenkittl, Thomas Stöggl and Erich Müller
This study evaluated the amount, and particularly, the structure of variability in postural control accompanying an unstable shoe (US) application. Mediolateral and anterior–posterior center of pressure signals plus electromyographic profiles of the tibialis anterior and gastrocnemius medialis were recorded in 29 asymptomatic men while wearing both US and flat shoes. Statistical analysis included common measures of dispersion as well as sample entropy and largest Lyapunov exponent estimates. Data were compared by two-way repeated-measures analysis of variance. Corresponding main effects of footwear revealed that, in contrast to the flat shoes condition, the US intervention consistently increased center of pressure and electromyographic net fluctuations and rendered the overall system less complex, as reflected by the lower sample entropy and higher Lyapunov exponent values observed throughout. Accordingly, employing US in stance should be functional concerning motor development; however, the greater sensitivity of US users to external perturbations must not be overlooked and warrants further investigation.
Gerold Sattlecker, Michael Buchecker, Christoph Gressenbauer, Erich Müller and Stefan J. Lindinger
To identify biomechanical predictors that distinguish between high- and low-score athletes in biathlon shooting and to determine the relationships among these variables in field testing.
Twenty-two biathletes (8 female, 14 male) from the World Cup, the European Cup, and a federal youth squad each fired 3 clips of 5 shots in prone and standing shooting positions without physical load, followed by 2 respective series in both disciplines during a simulated 12.5-km pursuit race on roller skis. Biomechanical variables describing triggering, rifle force in the back shoulder, and body and rifle sway were calculated over the last 0.5 second before firing. For computed linear discriminant analyses, subjects were divided into high- and low-level performers based on mean scores for each condition separately. In addition, correlations among all biomechanical factors were calculated.
Regarding prone shooting, shoulder force in the rest condition and vertical rifle sway in the race simulation were shown to be main discriminators. Several body- and rifle-sway variables were found to be predictors in standing rest shooting. Body sway across the shooting line discriminated the groups in the standing race situation tendentially. Thus, the main performance predictors changed due to fatigue. Correlations between triggering and rifle sway, shoulder force and rifle sway, and body sway and rifle sway were discovered.
Referring to the current results, athletes are recommended to focus on vertical rifle sway in prone position and on body sway across the shooting line during standing shooting when fatigued.