SOLVING INVERSE PROBLEMS IN BIOMECHANICS USING LEG EXTENSIONS AS AN EXAMPLE

Precise analysis of the muscle forces responsible for specific human movements represents a basic task in biomechanics. Here the focus is on gaining detailed information of the interplay between muscle forces and individual sports movements using inverse dynamics

INFLUENCE OF DIFFERENT KNEE MODELS ON CALCULATED MUSCLE FORCES

A basic task in biomechanics is the precise analysis of human movements and to investigate muscle forces that are responsible for these movements. Using inverse dynamics with a focus on the lower extremities the knee model type is of major interest. It is well known that the calculated muscle forces depend on the knee model type. With this study the influence of different knee model types and femoropatellar model types were investigated

TEACHING INTRODUCTORY AND ADVANCED BtOMECHANICS IN GERMANY AND THE UNITED STATES OF AMERICA

This paper will review differences and similarities of teaching biomechanics in Germany and the United States. Data of typical biomechanics course offerings in exercise sciencelsports science programs for both countries will be presented. Furthermore, the structure of course offerings will be discussed with respect to lecture/lab and active learning opportunities

FOOT POSITION AFFECTS KNEE JOINT TORQUE IN ERGOMETER ROWING

Recreational and competitive athletes use rowing ergometers for aerobic exercise. Little is known about the impact of foot position on knee joint loads during this exercise. The aim of this study was to investigate the effect of foot position on hip joint kinematics as well as knee adduction and knee rotation torques. It was hypothesized that altering the foot position to a more lateral placement on a rowing ergometer would mediate knee joint torques. Data supported the hypothesis that a significant change of knee adduction torque as well as reduced external rotation torques in the knee joint would accompany more lateral foot positioning. These results support the development of adjustable foot rests for rowing ergometers to better modulate knee forces

Xenophobia and Distribution in France: A Politico-economic Analysis

Anti-immigrant feeling (xenophobia) among voters has been proposed as a key factor explaining why, in the 2002 French national election, Jean Le Pen’s National Front Party won second place. Here, we study the effect of anti-immigrant sentiments among voters on the equilibrium position of political parties on the economic issue, which we take to be the size of the public sector. We model political competition among three parties (Left, Right, and Extreme Right) on a two-dimensional policy space (public sector size, immigration issue) using the PUNE model. We calibrate the model to French data for the election years 1988 and 2002, and show that politics have changed significantly over this period, from being centered primarily on economic issues to being centered on non-economic issues such as the immigration and security/law and order. We estimate that in 2002, the effect of voter xenophobia was to reduce the voters’ choice of public-sector size between 7% and 51% of one standard deviation of the population’s distribution of public-sector size ideal points, from what it would have been, absent xenophobia.Xenophobia, Racism, Distribution, Political equilibrium

MUSCULAR ACTIVITY IN COLLEGIATE FOOTBALL LINEMEN WITH AND WITHOUT A PREFABRICATED FUNCTIONAL KNEE BRACE

Functional knee braces are commonly used in the athletic realm in an attempt to prevent initial and reoccurring injuries. The purpose of this study is to evaluate muscular activity in collegiate football linemen during sport specific skills (3 point stance, lateral cutting maneuver, and drop jump). Ground Reaction force (GRF) and muscular activity of the quadriceps and hamstrings were analyzed to determine the impact of wearing a knee brace. Results showed no differences in the GRF or muscular activity of the quadriceps during any of the skills. The hamstring showed increased activity during the drop jump only. In conclusion, functional knee braces do not appear to negatively impact muscular activity during football specific drills

Distality of Attentional Focus and Its Role in Postural Balance Control

The role of attentional focusing in motor tasks has been highlighted frequently. The “internal–external” dimension has emerged, but also the spatial distance between body and attended location. In two experiments, an extended attentional focus paradigm was introduced to investigate distality effects of attentional foci on balance performance. First, the distality of the coordinates of the point of focus was varied between a proximal and distal position on an artificial tool attached to the body. Second, the distance of the displayed effect on the wall was varied between a 2.5 and 5 m condition. Subjects were instructed to focus on controlling either a proximal or distal spot on a tool attached to their head, represented by two laser pointers. Subsequently, they needed to visually track their own body-movement effect of one of the laser pointers at a wall while completing various single leg stance tasks. Center of pressure (COP) sway was analyzed using a linear method (classic sway variables) as well as a non-linear method (multiscale entropy). In addition, laser trajectories were videotaped and served as additional performance outcome measure. Experiment 1 revealed differences in balance performance under proximal compared to distal attentional focus conditions. Moreover, experiment 2 yielded differences in balance-related sway measures and laser data between the 2.5 and 5 m condition of the visually observable movement effect. In conclusion, varying the distality of the point of focus between proximal and distal impacted balance performance. However, this effect was not consistent across all balance tasks. Relevantly, the distality of the movement effect shows a significant effect on balance plus laser performance with advantages in more distal conditions. This research emphasizes the importance of the spatial distality of movement effects for human behavior

KINETICS OF THE LOWER EXTEREMITIES IN ERGOMETER ROWING DEPEND ON BODY MASS INDEX

The aim of this study was to investigate the influence of body mass index (BMI) on the kinetics of the lower extremities in ergometer rowing. Our results indicate that BMI has a major impact on lower extremity kinetics in ergometer rowing. Significantly increased knee joint torques with respect to external adduction and internal rotation were found. Furthermore, differences in hip and knee extension torques were found. The results indicate that obese individuals are at higher risk of overloading the knee joint during ergometer rowing

THE IMPACT OF BODY MASS AND SKILL LEVEL ON ROWING KINEMATICS

Rowing is a non-weight-bearing aerobic full body exercise, which is often recommended for weight loss programs. Previous studies demonstrated that Body Mass Index (BMI) is correlated with changes in the kinematics of humans. We extend this area of research to compare the effect of both BMI and skill-level on the kinematics of the lower extremities during rowing. Findings highlight differences such as knee flexion, knee internal rotation, hip extension, hip external rotation between normal weight and obese individuals. These findings suggest that injury risks are correlated to body type and previous skill level. This research indicates the need for adjustable setups for the rowing ergometer. This recommendation would not only increase comfort for all types of athletes, but reduce risks of injury and create the necessary conditions to accomplish a proper technique

ASPECTS OF A THREE DIMENSIONAL MOTION ANALYSIS OF THE VOLLEYBALL SPIKE IN HIGH LEVEL COMPETITION

The purpose of the study was a three dimensional motion analysis of the volleyball spike from position four during competition. Spikes were analysed at a tournament of the European league. Regarding the jump technique, only few athletes performed the discussed coordination pattern of the impulses within the body. It may be concluded that there exists reserves within the training process concerning the coordination in the takeoff phase even in high level athletes