Eva Janurová

Relationships between movements of the lower limb joints and the pelvis in open and closed kinematic chains during a gait cycle

Abstract Lots of athletic skills performed during practice or competition are initiated by the legs, where athletes either walk or run prior to executing specific skills. Kinematic chains are used to describe the relationships between body segments and joints during movement. The aim of this study was to determine the relationships between movements of lower limb segments and the pelvis in open and closed kinematic chains while walking. The experimental group consisted of 32 males (age 23.3 ± 2.5 years, body mass 78.1 ± 8.7 kg, body height 182 ± 6 cm). For 3D analysis, an optoelectronic system Vicon MX (7 cameras, frequency 200 Hz) was used. Positioning of the segments was determined by the PlugInGait Model. Each participant executed five trials at speeds ranging from 1.38 to 1.52 m·s-1. The relationships between angle variables of the lower limbs and the pelvis in selected gait cycle phases were evaluated using STATISTICA software (version 10.0) and the Spearman correlation. The highest numbers of moderate and large correlations were found at opposite toe off, heel rise and initial contact for the sagittal and transversal planes in comparison to the frontal plane. The closed kinematic chain had a stronger impact on determining the movement pattern. The instructions or interventions focusing on closed kinematic chain alternation are more effective for changes in a movement pattern. The preferred limb initiates kinematics in the direction of propulsion, while the non-preferred limb in internal and external rotation.

Kinematic Chains in Ski Jumping In-run Posture

Abstract The concept of kinematic chains has been systematically applied to biological systems since the 1950s. The course of a ski jump can be characterized as a change between closed and open kinematic chains. The purpose of this study was to determine a relationship between adjacent segments within the ski jumper’s body’s kinematic chain during the in-run phase of the ski jump. The in-run positions of 267 elite male ski jumpers who participated in the FIS World Cup events in Innsbruck, Austria, between 1992 and 2001 were analyzed (656 jumps). Two-dimensional (2-D) kinematic data were collected from the bodies of the subjects. Relationships between adjacent segments of the kinematic chain in the ski jumper’s body at the in-run position are greater nearer the chain’s ground contact. The coefficient of determination between the ankle and knee joint angles is 0.67. Changes in the segments’ positions in the kinematic chain of the ski jumper’s body are stable during longitudinal assessment. Changes in shank and thigh positions, in the sense of increase or decrease, are the same.

Testing of the High-Velocity Water Jetting on Concrete Samples Inside the Overpressure Vessel

The concrete samples with various erosion states were disintegrated inside the overpressure vessel using high-velocity water jet. Their erosion states were prepared by application of several laboratory techniques simulating the concrete aging under the natural conditions due to the real applications in practice. The influence of the erosion state on the disintegration rate was tested and the surface topography was studied both prior the application of water jet and post it. The water jet was applied in the overpressure vessel used for simulation of pressures equivalent to the submersion to several depths under the water level. Usual experimental scale responsive to the national practical application range was from the depth of submersion close to the water level up to the depth about 100 meters with the 20 meters step. Nevertheless, the data were obtained for overpressures equivalent to the submersion levels up to 140 meters enlarging so the range of results useful for regression analysis of the physical trend. Several samples were tested even in overpressures simulating depth of submersion equal to 160 meters and more. Few samples of special decorative concretes were also studied and special techniques of their working up were prepared and tested. All results are discussed regarding their application in practice and further development of special routings.Copyright