No abstract

No abstract

SUMMARY The purpose of this study was to test the hypothesis that runners having different running economies show differences in the mechanical and morphological properties of their muscle-tendon units (MTU) in the lower extremities. Twenty eight long-distance runners (body mass: 76.8±6.7 kg, height: 182±6 cm, age: 28.1±4.5 years) participated in the study. The subjects ran on a treadmill at three velocities (3.0, 3.5 and 4.0 m s-1) for 15 min each. The \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{V}}_{\mathrm{O}_{2}}\) \end{document}consumption was measured by spirometry. At all three examined velocities the kinematics of the left leg were captured whilst running on the treadmill using a high-speed digital video camera operating at 250 Hz. Furthermore the runners performed isometric maximal voluntary plantarflexion and knee extension contractions at eleven different MTU lengths with their left leg on a dynamometer. The distal aponeuroses of the gastrocnemius medialis (GM) and vastus lateralis (VL) were visualised by ultrasound during plantarflexion and knee extension, respectively. The morphological properties of the GM and VL(fascicle length, angle of pennation, and thickness) were determined at three different lengths for each MTU. A cluster analysis was used to classify the subjects into three groups according to their \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{V}}_{\mathrm{O}_{2}}\) \end{document}consumption at all three velocities (high running economy, N=10;moderate running economy, N=12; low running economy, N=6). Neither the kinematic parameters nor the morphological properties of the GM and VL showed significant differences between groups. The most economical runners showed a higher contractile strength and a higher normalised tendon stiffness (relationship between tendon force and tendon strain) in the triceps surae MTU and a higher compliance of the quadriceps tendon and aponeurosis at low level tendon forces. It is suggested that at low level forces the more compliant quadriceps tendon and aponeurosis will increase the force potential of the muscle while running and therefore the volume of active muscle at a given force generation will decrease.

The dislocation of a total hip endoprosthesis is an emotionally traumatizing event that should be prevented if possible. Preoperative risk assessment should be performed and the operation should be performed with optimal technique, including the best possible physical configuration of implant components, soft-tissue balance, and an adequately experienced orthopedic surgeon.

No abstract

Muscular co-activation was the main mechanical parameter related to cartilage changes. The current investigation elucidates the interaction of factors related to cartilage degeneration on an individual basis. Applications to altered loading conditions such as equipment or training methods offer an auspicious way of quantifying effects of interventions.

The results highlight the important role of KS on the interaction between trunk angle, joint kinetics, and postural dynamic stability during landing and show that ACL-reconstructed patients use an analogous feedforward strategy (e.g., more flexed trunk) to that used in their ACL-deficient state, aiming to compensate for KS deficits and thereby sacrificing postural dynamic stability and increasing the risk of loss of balance during landing maneuvers.

No abstract