Refine
Document Type
- Article (14)
- Doctoral Thesis (2)
Language
- English (14)
- German (1)
- Multiple languages (1)
Has Fulltext
- yes (16)
Keywords
- Classification (1)
- Dimensionality reduction (1)
- Elektromagnetische Induktion (1)
- Feature selection (1)
- GAT-1 (1)
- GAT-3 (1)
- GlyT1 (1)
- Hippocampus (1)
- Induktionsschweißen (1)
- Inferior colliculus (1)
Faculty / Organisational entity
Whole-body electromyostimulation (WB-EMS) is an extension of the EMS application known in physical therapy. In WB-EMS, body composition and skinfold thickness seem to play a decisive role in influencing the Ohmic resistance and therefore the maximum intensity tolerance. That is why the therapeutic success of (WB-)EMS may depend on individual anatomical parameters. The aim of the study was to find out whether gender, skinfold thickness and parameters of body composition have an influence on the maximum intensity tolerance in WB-EMS. [Participants and Methods] Fifty-two participants were included in the study. Body composition (body impedance, body fat, fat mass, fat-free mass) and skinfold thicknesses were measured and set into relation to the maximum intensity tolerance. [Results] No relationship between the different anthropometric parameters and the maximum intensity tolerance was detected for both genders. Considering the individual muscle groups, no similarities were found in the results. [Conclusion] Body composition or skinfold thickness do not seem to have any influence on the maximum intensity tolerance in WB-EMS training. For the application in physiotherapy this means that a dosage of the electrical voltage within the scope of a (WB-) EMS application is only possible via the subjective feedback (BORG Scale).
Die induktive Erwärmung stellt insbesondere aufgrund der schnellen intrinsischen Erwärmung eine Schlüsseltechnologie für die zunehmende industrielle Anwendung von textilverstärkten CFK-Organoblechen dar. Allerdings kann deren großes Potenti-al nicht vollständig ausgeschöpft werden, da sich bei konventionellen CFK-Organoblechen über der Laminatdicke physikalisch bedingt eine mit zunehmendem Abstand zum Induktor abfallende Temperaturkurve ergibt. Speziell für CFK-Organobleche bestehend aus textilen Verstärkungshalbzeugen wurde im Rahmen dieser Arbeit zunächst der Einfluss der Textil- und Laminatparameter grundlegend untersucht. Zusätzlich wurde ein analytisches Modell in Form eines elektrischen Er-satzschaubilds einer im CFK-Organoblech vorliegenden Leiterschleife entwickelt, an-hand dessen der dominierende Heizmechanismus identifiziert werden kann. Ab-schließend wurde basierend auf den zuvor gewonnenen Erkenntnissen ein speziell für das kontinuierliche Induktionsschweißen angepasster Laminataufbau entwickelt und validiert.
The core muscles play a central role in stabilizing the head during headers in soccer. The objective of this study was to examine the influence of a fatigued core musculature on the acceleration of the head during jump headers and run headers. Acceleration of the head was measured in a pre-post-design in 68 soccer players (age: 21.5 ± 3.8 years, height: 180.0 ± 13.9 cm, weight: 76.9 ± 8.1 kg). Data were recorded by means of a telemetric 3D acceleration sensor and with a pendulum header. The treatment encompassed two exercises each for the ventral, lateral, and dorsal muscle chains. The acceleration of the head between pre- and post-test was reduced by 0.3 G (p = 0.011) in jump headers and by 0.2 G (p = 0.067) in run headers. An additional analysis of all pretests showed an increased acceleration in run headers when compared to stand headers (p < 0.001) and jump headers (p < 0.001). No differences were found in the sub-group comparisons: semi-professional vs. recreational players, offensive vs. defensive players. Based on the results, we conclude that the acceleration of the head after fatiguing the core muscles does not increase, which stands in contrast to postulated expectations. More tests with accelerated soccer balls are required for a conclusive statement.
Muscular imbalances of the trunk muscles are held responsible for changes in body posture. At the same time, whole-body electromyostimulation (WB-EMS) has been established as a new training method that enables simultaneous stimulation of many muscle groups. This study was aiming to analyze if a 10 weeks WB-EMS training changes posture-relevant parameters and/or improves isometric strength of the trunk extensors and flexors, and if there are differences based on stimulation at 20 Hz and 85 Hz. Fifty eight untrained adult test persons were divided into three groups (control, CON; training with 20 Hz stimulation, TR20; training with 85 Hz, TR85). Anthropometric parameters, trunk extension and flexion forces and torques, and posture parameters were determined before (n = 58) and after (n = 53: CON: n = 15, TR20: n = 19, TR85: n = 19) a 10 weeks WB-EMS training program (15 applications, 9 exercises). Differences between the groups were calculated for pre- and post-tests using univariate ANOVA and between the test times using repeated (2 × 3) ANOVA. Comparisons of pairs were calculated post hoc based on Fisher (LSD). No differences between the groups were found for the posture parameters. The post hoc analysis of both trunk flexion and trunk extension forces and torques showed a significant difference between the groups TR85 and CON but no difference between the other group pairs. A 10 weeks whole-body electrostimulation training with a stimulation frequency of 85 Hz in contrast to training with a stimulation frequency of 20 Hz improves the trunk muscle strength of an untrained group but does not significantly change posture parameters.
Postural deficits such as hyperlordosis (hollow back) or hyperkyphosis (hunchback) are relevant health issues. Diagnoses depend on the experience of the examiner and are, therefore, often subjective and prone to errors. Machine learning (ML) methods in combination with explainable artificial intelligence (XAI) tools have proven useful for providing an objective, data-based orientation. However, only a few works have considered posture parameters, leaving the potential for more human-friendly XAI interpretations still untouched. Therefore, the present work proposes an objective, data-driven ML system for medical decision support that enables especially human-friendly interpretations using counterfactual explanations (CFs). The posture data for 1151 subjects were recorded by means of stereophotogrammetry. An expert-based classification of the subjects regarding the presence of hyperlordosis or hyperkyphosis was initially performed. Using a Gaussian progress classifier, the models were trained and interpreted using CFs. The label errors were flagged and re-evaluated using confident learning. Very good classification performances for both hyperlordosis and hyperkyphosis were found, whereby the re-evaluation and correction of the test labels led to a significant improvement (MPRAUC = 0.97). A statistical evaluation showed that the CFs seemed to be plausible, in general. In the context of personalized medicine, the present study’s approach could be of importance for reducing diagnostic errors and thereby improving the individual adaptation of therapeutic measures. Likewise, it could be a basis for the development of apps for preventive posture assessment.
The objectification of acute fatigue (during isometric muscle contraction) and cumulative fatigue (due to multiple intermittent isometric muscle contractions) plays an important role in sport climbing. The data of 42 participants were used in the study. Climbing performance was operationalized using maximal climbing-specific holding time (CSHT) by performing dead hangs. The test started with an initial measurement of handgrip strength (HGS) followed by three intermittent measurements of CSHT and HGS. During the test, finger flexor muscle oxygen saturation (SmO2) was measured using a near-infrared spectroscopy wearable biosensor. Significant reductions in CSHT and HGS could be found (p < 0.001), which indicates that the consecutive maximal isometric holding introduces cumulative fatigue. The reduction in CSHT did not correlate with a reduction in HGS over multiple consecutive maximal dead hangs (p > 0.35). Furthermore, there were no significant differences in initial SmO2 level, SmO2 level at termination, SmO2 recovery, and mean negative slope of the SmO2 saturation reduction between the different measurements (p > 0.24). Significant differences were found between pre-, termination-, and recovery- (10 s after termination) SmO2 levels (p < 0.001). Therefore, monitoring acute fatigue using athletes’ termination SmO2 saturation seems promising. By contrast, the measurement of HGS and muscle oxygen metabolism seems inappropriate for monitoring cumulative fatigue during intermittent isometric climbing-specific muscle contractions.
Heading in Soccer: Does Kinematics of the Head‐Neck‐Torso Alignment Influence Head Acceleration?
(2021)
There is little scientific evidence regarding the cumulative effect of purposeful heading. The head-neck-torso alignment is considered to be of great importance when it comes to minimizing potential risks when heading. Therefore, this study determined the relationship between head-neck-torso alignment (cervical spine, head, thoracic spine) and the acceleration of the head, the relationship between head acceleration and maximum ball speed after head impact and differences between head accelerations throughout different heading approaches (standing, jumping, running). A total of 60 male soccer players (18.9 ± 4.0 years, 177.6 ± 14.9 cm, 73.1 ± 8.6 kg) participated in the study. Head accelerations were measured by a telemetric Noraxon DTS 3D Sensor, whereas angles for the head-neck-torso alignment and ball speed were analyzed with a Qualisys Track Manager program. No relationship at all was found for the standing, jumping and running approaches. Concerning the relationship between head acceleration and maximum ball speed after head impact only for the standing header a significant result was calculated (p = 0.024, R2 = .085). A significant difference in head acceleration (p < .001) was identified between standing, jumping and running headers. To sum up, the relationship between head acceleration and head-neck-torso alignment is more complex than initially assumed and could not be proven in this study. Furthermore first data were generated to check whether the acceleration of the head is a predictor for the resulting maximum ball speed after head impact, but further investigations have to follow. Lastly, we confirmed the results that the head acceleration differs with the approach.
Study aim: To find out, without relying on gait-specific assumptions or prior knowledge, which parameters are most important for the description of asymmetrical gait in patients after total hip arthroplasty (THA).
Material and methods: The gait of 22 patients after THA was recorded using an optical motion capture system. The waveform data of the marker positions, velocities, and accelerations, as well as joint and segment angles, were used as initial features. The random forest (RF) and minimum-redundancy maximum-relevance (mRMR) algorithms were chosen for feature selection. The results were compared with those obtained from the use of different dimensionality reduction methods.
Results: Hip movement in the sagittal plane, knee kinematics in the frontal and sagittal planes, marker position data of the anterior and posterior superior iliac spine, and acceleration data for markers placed at the proximal end of the fibula are highly important for classification (accuracy: 91.09%). With feature selection, better results were obtained compared to dimensionality reduction.
Conclusion: The proposed approaches can be used to identify and individually address abnormal gait patterns during the rehabilitation process via waveform data. The results indicate that position and acceleration data also provide significant information for this task.
Neuronal inhibition is mediated by glycine and/or GABA. Inferior colliculus (IC) neurons receive glycinergic and GABAergic
inputs, whereas inhibition in hippocampus (HC) predominantly relies on GABA. Astrocytes heterogeneously
express neurotransmitter transporters and are expected to adapt to the local requirements regarding neurotransmitter
homeostasis. Here we analyzed the expression of inhibitory neurotransmitter transporters in IC and HC astrocytes using
whole-cell patch-clamp and single-cell reverse transcription-PCR. We show that most astrocytes in both regions expressed
functional glycine transporters (GlyTs). Activation of these transporters resulted in an inward current (IGly) that
was sensitive to the competitive GlyT1 agonist sarcosine. Astrocytes exhibited transcripts for GlyT1 but not for
GlyT2. Glycine did not alter the membrane resistance (RM) arguing for the absence of functional glycine receptors (GlyRs).
Thus, IGly was mainly mediated by GlyT1. Similarly, we found expression of functional GABA transporters (GATs) in all IC
astrocytes and about half of the HC astrocytes. These transporters mediated an inward current (IGABA) that was sensitive to
the competitive GAT-1 and GAT-3 antagonists NO711 and SNAP5114, respectively. Accordingly, transcripts for GAT-1 and
GAT-3 were found but not for GAT-2 and BGT-1. Only in hippocampal astrocytes, GABA transiently reduced
RM demonstrating the presence of GABAA receptors (GABAARs). However, IGABA was mainly not contaminated
by GABAAR-mediated currents as RM changes vanished shortly after GABA application. In both regions, IGABA
was stronger than IGly. Furthermore, in HC the IGABA/IGly ratio was larger compared to IC. Taken together, our
results demonstrate that astrocytes are heterogeneous across and within distinct brain areas. Furthermore, we
could show that the capacity for glycine and GABA uptake varies between both brain regions.
Die Ergebnisse der vorliegenden Synopsis konnten an vergleichsweise hohen Probandenzahlen zeigen, dass die auftretenden Amplituden der Kopfbeschleunigungen stark von der Herangehensweise (Stand, Sprung, Lauf) abhängen. Was zunächst trivial erscheint, ist nun evidenzbasiert und von hoher praktischer Relevanz. Bei der Technikvermittlung sind somit zunächst Kopfballvarianten aus der Standposition vorzuziehen, da diese zu einer geringeren Beschleunigung des Kopfes führen als Varianten welche mit einem Anlauf gekoppelt werden (Stand vs. Sprung). Kopfballvarianten mit einem erhöhten koordinativen Anforderungsprofil (Sprung) führen nicht zwangsläufig zu einer erhöhten Kopfbeschleunigung, sollten jedoch aus methodischen Gründen trotzdem zu einem späteren Zeitpunkt trainiert werden. Das eingesetzte Kopfballpendel führte zu Kopfbeschleunigungen zwischen 5.2 und 7.8 G. Diese Werte liegen deutlich unterhalb derer, die bei beschleunigten Bällen gemessen werden, was für den Einsatz des Kopfballpendels bei der Technikschulung spricht. Der Rumpfmuskulatur wird eine große Bedeutung bei der technischen Umsetzung von Kopfbällen zugesprochen [120]. Die vorliegenden Ergebnisse konnten jedoch keinen Anstieg der Kopfbeschleunigung nach Ermüdung der Rumpfmuskulatur darlegen. Ein Pre-Post-Vergleich bei beschleunigten Bällen muss folgen, um dies weiterführend untersuchen zu können. Vergleichbare Ergebnisse und Interpretationen liegen nun zur Wirksamkeit einer 6-wöchigen Hals-Nackenkräftigung vor, welche bei dem statischen Kopfballpendel keine Änderungen der Kopfbeschleunigung zur Folge hatten. Kritisch reflektiert werden müssen insbesondere die Art und Dauer sowie die Inhalte einer solchen Intervention. Dennoch steckt hinter dieser Hypothese weiterhin ein vielversprechender Ansatz das Kopfballspiel sicherer zu machen. Die Ausrichtung des Kopf-Hals-Rumpfsegmentes steht in keinem direkten Zusammenhang zur resultierenden Beschleunigung des Kopfes, wonach eine erhöhte Nickbewegung nicht mit einer erhöhten Kopfbeschleunigung korreliert. Im nächsten Schritt muss ein intraindividueller Vergleich vorgenommen werden, da die Kompensationsmechanismen höchst individuell sind. Außerdem sollte zukünftig die maximale Kopfbeschleunigung - unabhängig von dem Zeitpunkt - mit dem Winkel (Kopf, HWS) während des ersten Ballkontaktes verglichen werden, statt den zeitsynchronen Vergleich des Winkels und der in diesem Moment messbaren Kopfbeschleunigung vorzunehmen.