Anne Focke

The BioMotionBot: a robotic device for applications in human motor learning and rehabilitation.

Robotic manipulanda are an established tool for the investigation of human motor control and learning. Potentially, robotic manipulanda could also be valuable in the investigation of skill learning in more natural movement tasks. Most current designs have been developed for studying dynamic learning and rehabilitation and are restricted to 2D space. However, natural upper limb movements take place in 3D space, sometimes with high underlying forces. In this paper, we introduce a robotic device, the BioMotionBot, that can be used in established applications of dynamic learning and rehabilitation but also enables the investigation of skill learning in more natural 3D movement tasks with large dynamic perturbations. The design of the BioMotionBot is based on a mechanism with hybrid serial and parallel kinematics. We first describe the BioMotionBots mechanical design, the electronic components, the software structure and the control system. To investigate the performance of the BioMotionBot, its stiffness, endpoint mass, endpoint viscosity, haptic resolution, force depth and impedance ratio are evaluated. Additionally, we develop a detailed multi-body simulation model to validate aspects of the structure and behavior of the BioMotionBot. Finally, we present experimental data from a dynamic learning task in 2D and test a 3D scenario with virtual walls. Our results demonstrate that the BioMotionBot can be used for research in human motor learning and rehabilitation and also has potential for the investigation of skill learning in more natural 3D movement tasks.

Effects of age, sex and activity level on counter-movement jump performance in children and adolescents

Abstract The aim of this study was to investigate counter-movement jump performance and its reliability in children and adolescents with respect to age, sex and activity level. We tested 1835 children and adolescents aged between 4 and 17 years. All participants performed three counter-movement jumps on a force platform with arms akimbo. The participants were divided into six age groups and subdivided by sex within each group, to analyse age and sex effects. Subsequently, jumping performance of active and sedentary participants was compared. Jump height was calculated and the highest jump out of three was used for the calculations of peak force and peak rate of force development. Variability of all parameters was quantified using the coefficient of variation over all jumps. Jump height increased significantly with increasing age while peak rate of force development decreased. Peak force was similar for all age groups. Jump height was significantly higher in male participants and peak force and peak rate of force development was significantly lower in male participants. Variability of jump height and peak force decreased significantly with increasing age leading to reliable data above the age of 10 years. Peak rate of force development showed a high variability and, therefore, should be interpreted with caution. This could be useful information for coaches as they need to know from which age onwards the counter-movement jump is applicable in performance diagnostics and which parameters are sensible for interpretation. Finally, the present study provides data to be used as normative references.

Bilateral practice improves dominant leg performance in long jump

Abstract Benefits of bilateral practice both for the non-dominant and for the dominant body side have been shown in several studies. Thereby, most of the studies included movement tasks of the upper extremity or investigated sports games in which the ability of acting bilaterally is an essential basis for success and, thus, a bilateral practice is reasonable anyway. Individual unilaterally performed sports including movement tasks of the lower extremity are rarely investigated. Therefore, the aim of our study was to test if contralateral transfer due to bilateral practice can be found in an unilaterally performed sport including the lower extremity. We trained and tested 61 adolescent athletes in long jump to compare the jumping performance of the dominant leg after a 12-week practice period between two groups: a bilateral practice group that practiced specific long jump exercises with both the dominant and non-dominant leg and an unilateral practice group that practiced specific long jump exercises only with the dominant leg. Results showed a superior effect of bilateral practice compared to unilateral practice regarding the jumping performance of the dominant leg. The performance increase at post-test and retention-test for the dominant limb was significantly higher for the bilateral practice group (pre-to-post: 5.2%, pre-to-retention: 7.4%) compared to the unilateral practice group (pre-to-post: 3.4%, pre-to-retention: 4.5%). Thus, bilateral practice should be established in the early practice programmes of track and field athletes to improve the performance of the dominant take-off leg.