DETECTION OF BIOMECHANICAL ADAPTATION IN TREADMILL RUNNING

This study aims to propose a procedure for the detection of adaptation to treadmill running regarding biomechanical variables. Male novices in treadmill running (n=12) participated in one session of treadmill running while 3D motion analysis was executed. Statistical and analytical analyses supplemented with optimization algorithms within the proposed approach were applied to 14 common biomechanical variables. Overall, a low number of adapting data set was found. Even though adaptation has possibly been overrated, these processes have to be considered if study outcome might be influenced. However, due to unsystematic occurrence of adaptation, familiarization to treadmill condition cannot be generalized within a test group

THE 2D TROCHANTER TRACKING METHOD: A LOW COST ALTERNATIVE WHEN ASSESSINGVERTICAL POWER-FORCE-VELOCITY PROFILES?

Power force velocity profiles of ballistic push offs are increasingly more used for the purpose of performance assessment. The main input parameter for such profiles is jump height. This study aims to propose and validate a simple low cost method for calculating jump heights based on 2D tracking of the trochanter. Furthermore a comparison with the existing low cost time in air method was carried out. Twelve athletes performed squat jumps on a force platform and were simultaneously filmed with a high speed camera. The error analysis depicted increased accuracy and precision as well as slightly stronger relation to the criterion for the 2D trochanter tracking compared to the time in air method. The result can be explained by the fact that the landing position of the athlete has no influence on the jump height calculation when using the trochanter tracking method

VERTICAL POWER-FORCE-VELOCITY PROFILING: RELIABILITY COMPARISON OF MULITPLE- AND TWO-POINT METHODS

Power-Force-velocity (P-F-v) profiling is an approach used for performance diagnostics to assess an athlete’s anaerobic performance level. The aim of the study was to determine and compare the test-retest reliability of the 5p-method and the 2p-method for a group of sport students. With respect to the 2p-method this was the first study to determine the reliability using an independent data-set for vertical jumps. Acceptable reliability (ICC \u3e 0.78, CV \u3c 7.6%, no significant differences) was obtained for the variables F0, v0 and Pmax obtained through the 5p-method. Using the 2p-method acceptable reliability was just found for the variables F0 and Pmax. Therefore, the use of the 5p-method is recommended for performance diagnostics and derived individualized training regimes based on these P-F-v profiling results, as well as for research on this topic involving populations similar to sport students

CRITERION VALIDITY OF THE LOWER LIMB ISOKINETIC POWER-FORCE-VELOCITY PROFILING PARAMETERS IN ELITE ATHLETES

The purpose of this study was to investigate the criterion validity of isokinetic leg press Power-Force-velocity (P-F-v) parameters. Forty elite athletes with diverse sporting backgrounds performed a maximal vertical squat jump test and an isokinetic leg press P-F-v profile test. The isokinetic leg press P-F-v profile consisted of leg-extension against 4 given velocity conditions: 0.1, 0.3, 0.7, and 1.2 m/s. Criterion validity was evaluated using correlation between squat jump height and each isokinetic P-F-v parameter (F0, v0, Pmax and, Sfv). Nearly “good” (r \u3e 0.815) correlations were found for Pmax, whereas correlations between the remaining P-F-v parameters ranged from “poor” to “impractical” (r = 0.702– 0.159). This result may fit the previous assumption of P-F-v profiles, that individuals express variable contributions of F0 and v0 for similar Pmax values. Consequently evaluating criterion validity for these parameters (F0 and v0) is likely difficult would be contrary to this P-F-v assumption

BIOMECHANICAL PERFORMANCE DIAGNOSTICS: CONCEPTS AND APPLICATIONS IN SKI-JUMPING

This paper presents an overview regarding the evaluation of existing biomechanical measurement methods regarding their feasibility of application in biomechanical performance diagnostics (BPD) in ski-jumping. Depending on the purpose of the BPD different biomechanical measurement systems have been developed and applied. Force plates as well as pressure insoles are used to assess the kinetics during hill jumps and dry land exercises. Using an inverse dynamics approach, ground reaction forces can be calculated during take-off (hill jumps and imitation jumps) based on the kinematic information. Inertial measurement units provide the opportunity to determine the orientation of the skis during flight. In order to select adequate measurement systems based on the purpose of the BPD advantages and disadvantages have to be considered

Sidecut radius and the mechanics of turning—equipment designed to reduce risk of severe traumatic knee injuries in alpine giant slalom ski racing.

Background: There is limited empirical knowledge about the effect of ski geometry, particularly in the context of injury prevention in alpine ski racing. We investigated the effect of sidecut radius on biomechanical variables related to the mechanics of turning. Methods: During a field experiment, six European Cup level athletes skied on three different pairs of giant slalom (GS) skis varying in sidecut radii (30 m, 35 m and 40 m). Using a video-based three-dimensional (3D) kinematic system, a 22-point body segment model of the athletes was reconstructed in 3D, and the variables ground reaction force, centre of mass (COM) speed, COM turn radius, ski turn radius, edge angle, fore/aft position and skid angle were calculated. Results: While steering out of the fall line after gate passage, ground reaction force significantly differed between the 30 m and 40 m skis and between the 35 m and 40 m skis. These differences were mainly explainable by larger COM turn radii when skiing on the 40 m ski. During the same turn phase, significant differences in ski turn radius also were found, but there were no differences in edge angle, fore/aft position and skid angle. Summary: The sidecut-induced reduction in ground reaction force and the sidecut-induced increase in centre of mass and ski turn radius observed in this study provides indirect evidence of reduced self-steering of the ski. Self-steering plays a central role in the mechanism of anterior cruciate ligament rupture in alpine ski racing

BIOMECHANICAL AND METABOLIC EFFECTS OF A LEAF SPRING STRUCTURED MIDSOLE IN OVERGROUND RUNNING

A leaf spring structured midsole shoe (LEAF) increases stride length and reduces stride rate by a horizontal foot shift during stance phase in heel-toe running and leads to an enhanced economy in treadmill running. The purpose of this study was to investigate whether these effects can also be seen in overground running. Ten male runners ran with a LEAF and a standard foam midsole shoe (FOAM) at 2 mmol/l blood lactate. Stride rate and stride length were measured by an inertial measurement unit combined with a 2D video. Running economy was quantified via spirometry. The LEAF revealed a reduction in stride rate (-0.01±0.00Hz;

TECHNIQUE TRAINING IN ALPINE SKI RACING: FORCED MOVEMENT CHANGES BY A SPECIFIC DEVICE

A crucial point of modern methods in motor learning is a high degree of exercise variability. Especially in alpine skiing, where athletes have to compensate external variability, adequate exercises have to be offered. To fulfill these requirements, a specific training device with the possibility of different settings was developed. In the present study we analyzed the function of three settings and short time adaptation effects during a training session. A mixed training protocol (race & various device settings) was compared to a normal training session. In two of three settings runtimes were significantly higher. A repeated usage of one setting led to an adaptation in runtime (sig. faster). For partial runtimes no adaptation was found. No adaptation of the original race setup was observed after applying several variable settings. The overall force distribution between inside and outside leg was not, or only marginally, influenced by the usage of the device. Very strong effects were found in the force distribution within a leg. It can be concluded that the usage has only little impact on general movement patterns (macroscopic level), but a substantial one on microscopic level. Hence, the new device generates exactly those movement variations which are recommended for modern technique training

APPLIED BIOMECHANICS IN ALPINE SKIING-PAST, PRESENT AND FUTURE ISSUES

Biomechanics in alpine skiing has always been studied from an applied point of view. Among others biomechanical studies in alpine skiing can be categorised into the groups (1) biomechanical description and functional aspects of alpine skiing, (2) biomechanical analysis and determination of parameters related to pertormance in alpine skiing, (3) biomechanical testing, training and imitation exercises, (4) development, optimisation and tuning of the equipment, (5) modelling and simulation and (6) loading on the musculo-skeletal system and injuries in alpine skiing. This paper provides a literature review on biomechanics in alpine skiing with respect to these categorie

PEDAL FORCES, LOWER LIMB JOINT KINEMATICS AND KINETICS IN CYCLING WITH CIRCULAR AND NON-CIRULAR CHAINRINGS

Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity. Yet, scientific proof has failed to consistently reproduce the theoretical benefits in cycling trials. Therefore, the aim of this study was to analyse kinematics and kinetics between circular and two different shapes of non-circular chainrings. 14 elite cyclists pedalled at two submaximal (90 rpm: 180 W, 300 W) two-minutes cycling trials using three chainrings ranging from circular to ovality of 1.10 and 1.215. A significant increase of tangential pedal forces, sagittal ankle and hip joint moments and a significant decrease of sagittal knee joint moments were observed. Non-circular chainrings do not evidently seem to enhance performance, but facilitated conditions for muscle activation as well as a reduction of knee joint moments can occur