COMFORT AND PLANTAR PRESSURE PATTERN DURING RUNNING WITH PREFABRICATED INSOLES

The aim of this study was to investigate the relationship between plantar pressure pattern and wearing comfort of five different prefabricated insoles. Therefore wearing comfort was assessed by a questionnaire and the use of a visual analogue scale (VAS) and plantar pressure was measured by a Pedar-­X system. For statistical analysis single factor ANOVA for repeated measurements, Bonferroni and Pearson correlation test were performed. Significant differences in comfort ratings and average maximum plantar pressure were found. A relationship between average plantar pressure and comfort could not be detected. Nevertheless prefabricated insoles are able to improve wearing comfort of running shoes. Additional parameters like insole hardness and/or flexibility might also influence wearing comfort and seems to modulate the plantar pressure pattern during running

JOINT SPECIFIC MECHANICAL POWER DURING VERTICAL JUMPS OF ELITE BOBSLEIGH ATHLETES

The purpose of the study was to quantify jumping mechanics of elite male bobsleigh athletes (N=10; 28?3 yrs; 193?5 cm; 99?8 kg) performing two different kinds of vertical jumps (squat and countermovement). Kinetics and kinematics were measured with two force platforms (one per leg, 1080 Hz) and eight high-speed infrared cameras sampled at 120 Hz. Detection of the joint specific mechanical power generation pattern between legs and across athletes was realized via inverse-dynamic calculation. The results show an average jumping height of about 50 cm, which is associated with average body mass of almost 100 kg. An average joint specific contribution of mechanical power generation during squad and countermovement jumps could be determined close to one third per joint (hip, knee, ankle)

DETERMINANTS OF ACCELERATION PERFORMANCE IN ELITE FEMALE SPRINTERS

The purpose of this study was to explore the determinants of performance in the early acceleration phase (first four meters) in nine elite female sprinters. Acceleration performance was quantified using a modified version of the normalized average horizontal block power. Ground reaction forces were collected using an instrumented starting block and three force plates. In addition, full body kinematics were captured using an optoelectronic motion capture system. The results indicate that a starting technique facilitating a horizontal push-off direction and force application with short contact times is beneficial for starting performance. This might be achieved through a greater forward lean of the body. Previously proposed beneficial effects of an active touchdown of the foot could not be confirmed in the present study

DIFFERENCES BETWEEN TAKE-OFF BEHAVIOR DURING VERTICAL JUMPS AND TWO ARTISTIC ELEMENTS

The present study analysed the possible application of vertical jumps as a diagnostic tool for the acrobatic elements backward somersault (6s) and Menichelli (MEN). Therefore, 14 female gymnasts of the German national squad performed dassical vertical jumps (CMJ, SJ, DJ), backward somersaults and Menichellis during a diagnostic camp at the German Research Centre of Elite Sport (momentum). Kinematic and kinetic parameters were captured by a 30-motion capture system and two force plates. Take off velocities of the CMJ and backward somersault showed significant correlations (r=0.86). Besides possible predictions for take4ff velocity of BS performing CMJ, findings did not address execution of MEN. Concerning training purposes, vertical jumping does not affect performance characteristics of acrobatic elements

Evaluation of the performance of a motion capture system for small displacement recording and a discussion for its application potential in bone deformation in vivo measurements

The aim of this study is to evaluate the performance of a motion capture system and discuss the application potential of the proposed system in in vivo bone-segment deformation measurements. In this study, the effects of the calibration procedure, camera distance and marker size on the accuracy and precision of the motion capture system have been investigated by comparing the captured movement of the markers with reference movement. The results indicated that the system resolution is at least 20mm in a capture volume of 40033003300mm3, which mostly covers the range of motion of the tibia during the stance phase of one gait cycle. Within this volume, the system accuracy and precision decreased following the increase of camera distance along the optical axis of the cameras. With the best configuration, the absolute error and precision for the range of 20mm displacement were 1.2–1.8mm and 1.5–2.5mm, respectively. Small markers (Ø3–8 mm) yielded better accuracy and repeatability than the larger marker (Ø10.5mm). We conclude that the proposed system is capable of recording minor displacements in a relative large volume

LOWER SPINE LOADING AND PELVIC KINEMATICS THROUGHOUT A NEAR-MAXIMAL 10 KM RUN

The purpose of the present study was to investigate the effects of fatigue on lower back loading and pelvis kinematics in distance running. Kinetic and kinematic data of the whole body was recorded for 13 subjects during a near-maximal 10-km run. Pelvis kinematics were calculated in 3D while moments acting on the lumbar spine were determined by using a full body lumbar spine model in OpenSim. We found significant effects of running distance for pelvis kinematics in the transversal and sagittal plane whereas the lumbar spine moments increased significantly in the frontal and transversal plane. These results support earlier findings suggesting a connection between running and spinal or pelvic overuse injuries. Thus, distance runners should focus on a controlled arm swing and upper body rotation as well as pelvis stabilization

JOINT WORK OF THE TAKE-OFF LEG DURING ELITE HIGH JUMP

The purpose of the study was to evaluate kinematics and kinetics in elite high jumpers and to estimate joint work of the lower extremity with a custom-modified full-body model. Motions of seven male athletes (personal best 2.24 ± 0.06 m) during jumping were filmed with 19 Infrared-Highspeed-Cameras and ground reaction forces were captured with a force plate. The results show that knee joint energy absorption is twice as much as at the ankle joint (p 0.05) in energy generation between the knee and ankle joint, but the ankle joint generates more energy than it absorbs (p < 0.05). The problem-solving approach to raise the center of mass to 2.10 m was different between the jumpers

JOINT SPECIFIC CONTRIBUTION OF MECHANICAL POWER AND WORK DURING ACCELERATION AND TOP SPEED IN ELITE SPRINTERS

The purpose of the study was to quantify and compare sprint mechanics of elite female sprinters (N=9; PB 11.4?0.2s) during acceleration (1st, 2nd, 3rd step) and top speed (‘flying 30m) running. Three dimensional kinetics and kinematics were measured on an IAAF indoor track armed with four force plates and 16 cameras. The comparison between the 1st, 2nd and 3rd step and the ‘flying 30m’ (vave= 9.0?0.2 ms-1) shows a progressive change in absorption and generation of mechanical power. Whilst the knee extensors where able to minimize energy absorption during acceleration, the ankle extensors showed a stretch-shortening cycle and a small absorption from the first step. This energy loss at the ankle joint does not necessarily leads to a decrease in sprint performance, it also offers the plantar flexors to work in an stretch-shortening cycle instead of concentric only mode

LEG- AND JOINT STIFFNESS IN MALE ELITE HIGH JUMP: THE INFLUENCE OF STIFFNESS ON SPORTS PERFORMANCE

The purpose of this study was to analyse stiffness in the mechanical system of the world’s elite high jumpers. Seven male elite high jump athletes (personal best 2.24 m ± 0.06 m) were filmed with 19 Infrared-High-Speed-Cameras during jumping. Kinetics were captured with a force plate. It was found that a different leg and joint stiffness during takeoff enables nearly the same jumping height. For example, a typical power jumper with a leg stiffness of 543.6 N m-1 kg-1 reached 2.13 m, while a typical speed jumper with a leg stiffness of 1133.5 N m-1 kg-1 reached a comparable height of 2.12 m. Therefore, it seems that sports performance in single leg jumping is not limited by athlete’s leg and joint stiffness in a small group of male elite high jumpers

Tibia segment deformation in response to simulated muscle forces: a cadaveric study with a novel optical segment tracking (OST) approach

OBJECTIVES: A novel optical segment tracking (OST) approach reliant upon motion capturing was previously proposed to assess human tibia segment deformation. The purposes of the present study were to validate the OST approach and assess the contribution of muscular forces to the bone deformation in a well-defined ex vivo human model. METHODS: A custom-made Lower Extremity Loading Device (LELD) was developed to simulate physiological muscle contractions in six human cadaveric lower extremities. Tibia segment deformation was measured by tracking the relative movement between two marker clusters which were affixed into the proximal and distal tibia, respectively. RESULTS: Compared to the physiological norms, the simulated muscle forces remained at a low level. When quadriceps muscle was loaded with forces from 198 N to 505 N, posterior bending (0.12°-0.25°) and lateral bending (0.06°-0.21°) of the tibia segment were found. Large tibia bending angles were found when simulating the co-contraction of upper leg muscles and plantar flexors, and of all leg muscles, respectively. The standard deviations of the deformation angles between the repetitions remained at a low level. CONCLUSIONS: We conclude that the OST approach has the potential to be applied in vivo and quantify muscle-induced bone deformations