Gaspar Morey-Klapsing

Influence of the muscle-tendon unit's mechanical and morphological properties on running economy

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 effect of falling height on muscle activity and foot motion during landings.

The aims of this study were: (a) to examine the effect of falling height on the kinematics of the tibiotalar, talonavicular and calcaneocuboid joints and (b) to study the influence of falling height on the muscle activity of the leg during landings. Six female gymnasts (height: 1.63 +/- 0.04 m, weight: 58.21 +/- 3.46 kg) participated in this study. All six gymnasts carried out barefoot landings, falling from 1.0, 1.5 and 2.0 m height onto a mat. Three genlocked digital high speed video cameras (250 Hz) captured the motion of the left shank and foot. Surface electromyography (EMG) was used to measure muscle activity (1000 Hz) from five muscles (gastrocnemius medialis, tibialis anterior, peroneus longus, vastus lateralis and hamstrings) of the left leg. The kinematics of the tibiotalar, talonavicular and calcaneocuboid joints were studied. The lower-leg and the foot were modelled by means of a multi-body system, comprising seven rigid bodies. The falling height does not show any influence on the kinematics neither of the tibiotalar nor of the talonavicular joints during landing. The eversion at the calcaneocuboid joint increases with increasing falling height. When augmenting falling height, the myoelectric activity of the muscles of the lower limb increases as well during the pre-activation phase as during the landing itself. The muscles of the lower extremities are capable of stabilizing the tibiotalar and the talonavicular joints actively, restricting their maximal motion by means of a higher activation before and after touchdown. Maximal eversion at the calcaneocuboid joint increases about 52% when landing from 2.0 m.

Evidence of proactive forefoot control during landings on inclined surfaces.

The notion of proactive control of landings is generally accepted, and some underlying mechanisms have already been described. Only little is known on adjustments at the foot level, however. The authors therefore investigated the foot and ankle behavior of 24 participants as they landed on differently inclined surfaces. A 4-segment model of the foot and ankle provided 3-dimensional kinematics. They also analyzed activation patterns from several muscles and the ground reaction force. Participants anticipated the different surfaces, as shown by the forefoot kinematics and the activation patterns before touch down. Anticipation of the surface inclination led to adjustments in forefoot orientation and probably also in joint stiffness. The authors suggest that those adjustments tend to enhance the self-stabilizing potential of the mechanical system. The enhancement of that potential would ease the subsequent stabilization, reducing the demands on the neural system.

Commentaries on viewpoint: On the hysteresis in the human Achilles tendon.

114:518-520, 2013. ; J Appl Physiol Karamanidis and Sudarshan R. Nelatury Alexandre Foure, Christophe Cornu, Gaspar Morey-Klapsing, Lida Mademli, Kiros Maganaris, Rene B. Svensson, Christian Coupe, Andreas Hershenhan, Pernilla Eliasson, Adamantios Arampatzis, Mary C. Vagula, Andrew G. Cresswell, Constantinos N. Glen A. Lichtwark, Robert F. Ker, Neil D. Reeves, S. Peter Magnusson, Antoine Nordez, human Achilles tendon Commentaries on Viewpoint: On the hysteresis in the

Joint Stabilizing Response to Expected and Unexpected Tilts

Background: The results found in the literature regarding functional ankle joint stabilization are controversial possibly because of the testing methods used. Methods: The responses of 22 subjects to unexpected and expected sudden inversions of the foot were compared for all subjects together, as well as grouped by their self-perceived stability. A three-dimensional foot model was used to describe ankle and foot motion. Electromyographic signals of six muscles of the lower limb as well as the horizontal ground reaction forces were recorded.Results: Whereas unexpected and expected trials did not show significant differences (p > 0.05) in kinematics, higher activation and horizontal force integrals were found for the unexpected trials. In addition, no differences in electromyographic or ground reaction force parameters were found between stable and unstable ankles; however, the kinematics revealed higher amplitudes and velocities for the stable group. Conclusions: The awareness of the instant of tilt enhances stabilization in that the same motion is achieved with a lower muscle activation. Evidence suggests that this is triggered at supraspinal levels. We found that timing of the EMG signal is not as relevant to stabilization as the amplitude (which has often been disregarded in the literature).

Commentaries on Viewpoint: On the hysteresis in the human Achilles tendonINFERRING TENDON MECHANICAL PROPERTIES USING ULTRASOUND IMAGINGTHE HYSTERESIS OF TENDON, IN VITRO AND IN VIVOCOMMON PROBLEMS IN THE MEASUREMENT OF HUMAN TENDON HYSTERESIS IN VIVOVIEWPOINT: ON THE HYSTERESIS IN THE HUMAN ACHILLES TENDONON THE HYSTERESIS IN THE HUMAN ACHILLES TENDON: INFLUENCE OF THE LOADING RATE AND MUSCLE COORDINATIONCOMMENTARY ON VIEWPOINTSTIFFNESS AND HYSTERESIS OF HUMAN TENDONS

114:518-520, 2013. ; J Appl Physiol Karamanidis and Sudarshan R. Nelatury Alexandre Foure, Christophe Cornu, Gaspar Morey-Klapsing, Lida Mademli, Kiros Maganaris, Rene B. Svensson, Christian Coupe, Andreas Hershenhan, Pernilla Eliasson, Adamantios Arampatzis, Mary C. Vagula, Andrew G. Cresswell, Constantinos N. Glen A. Lichtwark, Robert F. Ker, Neil D. Reeves, S. Peter Magnusson, Antoine Nordez, human Achilles tendon Commentaries on Viewpoint: On the hysteresis in the