- Postural Control
- Adaption, Generalization and Consolidation of Human Motor Memory
- Biomechanics of Human Movements
- Sports Performance
Human posture is characterized by inherent instability arising from internal and external forces. Corrective intermuscular and intramuscular synergies, and thereby, coordination of several joints with multiple degrees of freedom are needed to counteract the destabilizing oscillations. This process of controlling the body’s position in space is based on complex interactions of dynamic processes predominantly relying on sensory input from the visual, vestibular and somatosensory systems. This information is passed on to different parts of the central nervous system, where it is integrated and dynamically re-weighted to provide an internal representation of the body and its environment. This representation is then used to generate and update the motor commands that maintain postural stability.
The overall complexity of human posture control becomes evident by the simple facts that a high center of mass must be maintained within a small base of support, that limitation of sensory information leads to dramatic increases in postural sway, and that postural control is affected by numerous factors, including health status, age or fatigue. Besides, recent studies have indicated beneficial physiological effects of concurrent jaw clenching activities on the stabilization of human posture, providing the basis for our research. The manifold significance of this research is reflected by epidemiological studies revealing that postural instability is a key risk factor for falls, finally emphasizing the general and socio-economic importance of this issue.
- Ringhof, S., Leibold, T., Hellmann, D. & Stein, T. (2015). Postural stability and the influence of concurrent muscle activation – Beneficial effects of jaw and fist clenching. Gait & Posture, 42 (4), 598-600.
- Hellmann, D., Stein, T., Potthast, W., Schindler, H.J. & Ringhof, S. (2015). The influence of force-controlled biting on human postural control. Human Movement Science, 44, 22-31.
- Ringhof, S., Stein, T., Potthast, W., Schindler, H.-J. & Hellmann, D. (2015). Force-controlled biting alters postural control in bipedal and unipedal stance. Journal of Oral Rehabilitation, 42 (3), 173-184.
Motor actions are constantly faced changes in the internal and external conditions. For instance, adding a big eraser to the top of a pencil changes its mechanical properties and the handwriting is affected. However, after some lines of practice, the handwriting regains its initial shape. Similarly, as muscles fatigue the internal conditions change. This illustrates that the CNS needs to adjust its motor commands to ensure task goal achievement. The property to regain a previous level of motor performance under altered conditions is called motor adaptation.
Another important feature of the CNS is the generalization (or transfer) of motor memory from one context or task to another. For example, a person who learned writing with a pen will also be able to write with chalk on a blackboard or even to write with the other hand.
Clearly, practice plays an important role in motor learning. However, practice alone is not sufficient to gain long-lasting expertise as newly formed motor memories are highly fragile. For this reason, newly formed motor memory needs to be stabilized and protected against forgetting and interfering factors – a process called consolidation.
Despite their importance, adaptation, generalization, and consolidation of motor memory are insufficiently understood. Yet, these processes and their underlying mechanisms are of high interest both for fundamental research and in applied settings. In particular, the interplay of these different capabilities is of interest – e.g., can adapted motor behavior be transferred to another effector and can such ability be consolidated?
- Taubert*, M., Stein*, T., Kreutzberg, T., Stockinger, C., Hecker, L., Focke, A., Ragert, P., Villringer, A. & Pleger, B. (2016). Remote effects of non-invasive cerebellar stimulation on error processing in motor re-learning. Brain Stimulation, 9, 692-699. [*both authors contributed equally]
- Thürer, B., Stockinger, C., Focke, A., Putze, F., Schultz, T., & Stein, T. (2016). Increased gamma band power during movement planning coincides with motor memory retrieval. NeuroImage, 125, 172-181.
- Stockinger, C., Thürer, B., Focke, A. & Stein, T. (2015). Intermanual transfer characteristics of dynamic learning: direction, coordinate frame, and consolidation of interlimb generalization. Journal of Neurophysiology, 114 (6), 3166-3176.
In different scientific disciplines a fine grained analysis of human movements is necessary to be able access movement patterns or joint loads during gait or upper body movements like object manipulations. We are therefore documenting movements of different body segments in three dimensions (kinematics) and complement this with information of acting forces from the ground (kinetics). The kinematic and kinetic information together with anthropometric information from the human subject are input sources for biomechanical multibody models allowing the calculation of joint mechanics and muscle activity.
We are using these methods in ergonomics for the analysis of different object manipulations in the context of manual assembly tasks to optimize workplace designs. Moreover, we are using these methods in orthopedics in the context of ruptures of the anterior cruciate ligament (ACL) to analyze the stabilizing effects of different knee braces or the changes in gait coordination during rehabilitation after an ACL reconstruction. Finally, we are analyzing the effects of knee braces on gait biomechanics in patients with knee osteoarthritis.
- Krafft, F. C., Stetter, B. J., Stein, T., Ellermann, A., Flechtenmacher, J., Eberle, C., Sell, S. & Potthast, W. (2017). How does functionality proceed in ACL reconstructed subjects? Proceeding of functional performance from pre- to six months post-ACL reconstruction. PLoS ONE, 12 (5): e0178430. https://doi.org/10.1371/journal.pone.0178430
- Graichen, S., Stein, T., Neff, C., Hoffmann, M. & Deml, B. (2015). Biomechanical Analysis of Manual Assembly Tasks. Zeitschrift für Arbeitswissenschaft, 69 (2), 105-112.
- Krafft, F. C., Eckelt, M., Köllner, A., Wehrstein, M., Stein, T. & Potthast, W. (2015). Reproducibility of spatio-temporal and dynamic parameters in various, daily occurring, turning conditions. Gait & Posture, 41 (1), 307–312. DOI: 10.1016/j.gaitpost.2014.09.007
Learning sport-specific skills generally covers a training process of several years. In most sports, also conditional capacities such as strength, endurance or speed are of great relevance. Based on multivariate statistical modelling approaches, our research group investigates the significance of individual performance components and its relationships with regard to the selected sports (e.g., triathlon).
To be able to diagnose the current individual performance level adequate diagnostic techniques and methods are necessary. Complex biomechanical motion analyses, physiological testings, and sports-related tests are some of such methods, which are developed and optimized in our laboratory (e.g., jump diagnostics).
In a third step, our lab develops and evaluates new and innovative training methods to increase efficiency of performance gains (e.g., athletics). Finally, results of this research strand are transferred into sports practice.
- Focke, A., Spancken, S., Stockinger, C., Thürer, B. & Stein, T. (2016). Bilateral practice improves domi-nant leg performance in long jump. European Journal of Sport Science 16 (7), 787-793.
- Ringhof, S., Hellmann, D., Meier, F., Etz, E., Schindler, H.J. & Stein, T. (2015). The effect of oral motor activity on the athletic performance of professional golfers. Frontiers in Psychology 6:750.
- Richter, A., Räpple, S., Kurz, G. & Schwameder, H. (2011). Counter movement jump in performance diagnostics. Use of the correct jumping technique. European Journal of Sport Science, 12 (3), 231-237. DOI: 10.1080/17461391.2011.566369