Evidence of different sensitivity of muscle and tendon to mechano-metabolic stimuli

This study aimed to examine the temporal dynamics of muscle-tendon adaptation and whether differences between their sensitivity to mechano-metabolic stimuli would lead to non-uniform changes within the triceps surae (TS) muscle-tendon unit (MTU). Twelve young adults completed a 12-week training intervention of unilateral isometric cyclic plantarflexion contractions at 80% of maximal voluntary contraction until failure to induce a high TS activity and hence metabolic stress. Each participant trained one limb at a short (plantarflexed position, 115°: PF) and the other at a long (dorsiflexed position, 85°: DF) MTU length to vary the mechanical load. MTU mechanical, morphological, and material properties were assessed biweekly via simultaneous ultrasonography-dynamometry and magnetic resonance imaging. Our hypothesis that tendon would be more sensitive to the operating magnitude of tendon strain but less to metabolic stress exercise was confirmed as tendon stiffness, Young's modulus, and tendon size were only increased in the DF condition following the intervention. The PF leg demonstrated a continuous increment in maximal AT strain (i.e., higher mechanical demand) over time along with lack of adaptation in its biomechanical properties. The premise that skeletal muscle adapts at a higher rate than tendon and does not require high mechanical load to hypertrophy or increase its force potential during exercise was verified as the adaptive changes in morphological and mechanical properties of the muscle did not differ between DF and PF. Such differences in muscle-tendon sensitivity to mechano-metabolic stimuli may temporarily increase MTU imbalances that could have implications for the risk of tendon overuse injury

INTERACTION BETWEEN THE POLE AND THE HUMAN BODY AND ITS EFFECT ON THE POLE VAULTING PERFORMANCE

The purposes of this study were: (a) to examine the utilization of pole elasticity by the athletes through muscular work and to develope performance criteria throughout the pole vault and (b) to examine the reproducibility and the athlete's specificity of the developed criteria. In the study, 6 athletes performed from 4 to 11 trials each, at 90% of their respective personal best performance. All trials were recorded using four synchronized, genlocked video cameras operating at 50 Hz. The ground reaction forces exerted on the bottom of the pole were measured using a planting box fixed on a kistler force plate (1000 Hz). The interaction between athlete and pole may be split into two parts. During the first part of the interaction, energy is transferred into the pole and the total energy of the athlete decreases. The difference between the energy decrease of the athlete and the pole energy indicates if the athletes are producing additional energy by means of muscular work (criterion 1). In the second part of the interaction, energy is transferred back to the athlete and the total energy of the athlete increases. The difference between the returned pole energy and the amount of energy increase of the athlete defines criterion 2. The criteria are reproducible, specific to each athlete, capable of identifying deficits or strengths of the athlete's performance during his interaction with the pole; they can therefore estimate the quality of the technique during each of the phases of the interaction athlete-pole

BIOMECHANICAL ANALYSIS OF THE HIGH JUMP AT THE SIXTH WCA IN ATHENS

Introduction: The main purposes of this study were 1. To determine the importance of initial conditions and take-off phase characteristics on jump performance. 2. To determine to what extent the initial conditions are effectively used by jumpers at the world class level. Methods: Data for this analysis were collected during the men’s high jump final competition at the 1997 Track and Field World Championships. A total of 26 successful jumps by 12 athletes were analyzed. The data was collected using 4 synchronized video cameras (50 Hz). Results and conclusions: On the basis of the total initial center of mass (CM) energy and the take-off characteristics, two relatively homogeneous groups could be identified. The take-off phase characteristics which are determined by the loss of CM energy during take-off and from the transformation of the approach energy to jump energy (transformation index) are very important for determining jump height. The initial energy of the CM determines the height an athlete can achieve. The actual jump height is strongly influenced by the take-off characteristics of the athlete. Both groups achieved the same jump height. Group 2 produced higher initial energy values. Group 1 demonstrated more efficient take-off characteristics. It was found that many athletes did not use their initial conditions optimally (Fig.1). The optimal energy decrease was calculated for the analyzed athletes as between 4 and 5 J/kg (Fig.1)

MEN'S AND WOMEN'S POLE VAULT AT THE SYDNEY 2000 OLYMPIC GAMES WITH RESPECT TO MECHANICAL ENERGY AND ANGULAR MOMENTUM

The purpose of this study was to identify differences between male and female pole vaulters with regard to the athlete's mechanical energy and angular momentum on elite level. On the basis of 3-D kinematic data of the pole vault finals at the Sydney Olympic Games the athlete's mechanical energy and angular momentum have been calculated. The development of the total, kinetic and potential energy shows similar characteristics for men and women. The initial energy of the vault, the energy at maximum pole bend position and the final energy are significantly higher for male athletes, while the energy gain produced by the athletes during the vault shows no significant differences. The angular momentum is higher for the female vaulters during the initial pole bend and the bar clearance

BlogForever D5.2: Implementation of Case Studies

This document presents the internal and external testing results for the BlogForever case studies. The evaluation of the BlogForever implementation process is tabulated under the most relevant themes and aspects obtained within the testing processes. The case studies provide relevant feedback for the sustainability of the platform in terms of potential users’ needs and relevant information on the possible long term impact

Differences in motor response to stability perturbations limit fall-resisting skill transfer

This study investigated transfer of improvements in stability recovery performance to novel perturbations. Thirty adults (20-53 yr) were assigned equally to three treadmill walking groups: groups exposed to eight trip perturbations of either low or high magnitude and a third control group that walked unperturbed. Following treadmill walking, participants were exposed to stability loss from a forward-inclined position (lean-and-release) and an overground trip. Lower limb joint kinematics for the swing phase of recovery steps was compared for the three tasks using statistical parametric mapping and recovery performance was analysed by margin of stability and base of support. The perturbation groups improved stability (greater margin of stability) over the eight gait perturbations. There was no group effect for stability recovery in lean-and-release. For the overground trip, both perturbation groups showed similar enhanced stability recovery (margin of stability and base of support) compared to controls. Differences in joint angle kinematics between treadmill-perturbation and lean-and-release were more prolonged and greater than between the two gait perturbation tasks. This study indicates that: (i) practising stability control enhances human resilience to novel perturbations; (ii) enhancement is not necessarily dependent on perturbation magnitude; (iii) differences in motor response patterns between tasks may limit transfer