List of Titles

An investigation into the force-EMG relationship for static and dynamic exertions

Authors: Koekemoer, Wesley Agosthinho
Date: 2022-04-06
Subjects: Electromyography , Force and energy , Muscles Physiology , Biomechanics , Muscle contraction , Isometric exercise , Isotonic exercise , ‎Static and dynamic exertions
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/291076 , vital:56816
Description: The force-EMG relationship has multiple applications in varying fields of study and practice. One such application is the development of safety guidelines and regulations. Current guidelines are based on static muscle actions even though the majority of tasks encountered in industry are dynamic in nature. This may have negative implications for the health, safety, and productivity of workers as regulations based on static muscle actions may place higher force demands on manual labourers compared to what would be expected if regulations were based on dynamic muscle actions. Regulations based on dynamic muscle actions may be more effective in worker safety as the nature of the regulation matches that of the demand. Few studies have investigated the force-EMG relationship during dynamic muscle actions and the few that do exist have reported contradictory / mixed results. Therefore, the purpose of this study was to: 1) gain an understanding of EMG responses at different load levels, and 2) show how the relationship differs between static and dynamic muscle actions. A two-factorial repeated-measures experiment was developed for this study. Eighteen experimental conditions, utilizing six load levels (0%, 20%, 40%, 60%, 80%, and 100% of maximum voluntary force) for each of the three muscle actions (isometric, concentric and eccentric). Surface EMG responses were obtained under these conditions by repeatedly dorsiflexing and plantarflexing the foot, thus activating the soleus muscle. A maximum voluntary exertion on an isokinetic dynamometer determined the maximum force level, based on which the sub-maximal loads were calculated and added to a pulley system. 31 student participants were recruited for this experiment which was conducted over two sessions – one information and habituation session, and one experimental session. The EMG data recorded were processed and checked for normality and outliers. The data was then analysed via a General Linear Model analysis to determine the effect of exertion type and of load level on the muscle activity. Significant differences were identified at p<0.05 and followed by a Tukey post-hoc test. Correlation analyses were also conducted to determine the relationship between the force and EMG at all three exertion types. All dependent measures showed that as the load level increased so did the sEMG amplitude for all muscle actions. Muscle actions differed significantly between majority of six force levels. Correlations between the load levels and sEMG amplitude for each muscle action indicated a significant correlation with a moderate strength. The conclusion draws from this study that there is a positive correlation between force and sEMG amplitude, at all load levels, with a moderate strength. However, the muscle actions differed significantly from each other. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2022
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Date Issued: 2022-04-06

An analysis of intrasemiotic and intersemiotic relations of textual and visual modes in Namibian school science textbooks

- Mateus, Venasius

Authors: Mateus, Venasius
Date: 2021-04
Subjects: Science -- Study and teaching (Secondary) -- Namibia , Semiotics , Force and energy , Visual learning , Verbal learning , Functionalism (Linguistics) , Science -- Textbooks
Language: English
Type: thesis , text , Masters , MEd
Identifier: http://hdl.handle.net/10962/177203 , vital:42799
Description: Although science education in Namibia receives much attention, learners’ performance is low in subjects such as Physical Sciences. The topic of Forces is among the topics in Physical Sciences where learners perform poorly. The provision of basic education in Namibia faces many challenges. One of these is that many teachers are not fully qualified for teaching the subjects they currently teach. Another (possibly related) challenge is that the majority of teachers in Namibian schools rely heavily on school textbooks when planning their lessons. In addition, learners use school textbooks as learning aids. The textbooks are developed and published in the private sector and based on the national curriculum statements. Quality of education has been amongst the major goals of education in Namibia. For quality assurance purposes, school science textbooks have to undergo a formal evaluation process. School textbooks, especially science textbooks, are multimodal. This means that they are designed with various modes, such as the textual and visual, often used in expressing scientific meanings. Literature reveals the textual and visual as individual modes having their own affordances, however, when integrated in school science textbooks contribute to strengthened meanings. No study published was found in Namibia or elsewhere that focused on analysing the intrasemiotic and intersemiotic sense relations of the textual and visual modes in Namibian school Physical Sciences textbooks. This study therefore aimed at contributing to filling this knowledge gap. The research is a qualitative case study and employed the interpretive paradigm. The selected Physical Sciences textbooks that constitute the data in this study were explored in depth via document analysis. Related textual and visual modes in the Physical Sciences textbooks were analysed in order to help answer the research questions of the study. Systemic Functional Linguistics was employed as the theoretical underpinning for this study. In this study, the sense relations were explored in terms of the sense relation themes which were coded and developed from common features of scientific discourse. The results reveal that scientific knowledge within the textual mode in the topic of Forces is communicated mostly through synonymy and repetition while within the visual mode it is mostly through antonymy, collocation, and synonymy. This contributed to meaning potential in the topic of Forces for the three Physical Sciences textbooks. The results further indicated that the overall cohesion within the textual and visual modes in the topic of Forces is achieved since repetition, which is the most direct form of lexical cohesion together with synonymy, collocation, and antonymy which are aspects of cohesion, occurred most frequently within these modes. This result further indicates that meaning potential in the topic of Forces in the three Physical Sciences textbooks were strengthened. While some sense relations occurred most frequently within individual modes, they were less frequent in other modes and vice versa. This indicates that different modes have different affordances. Finally, it was found that combining the textual and visual modes in the topic of Forces contributes to intersemiotic complementarity being achieved through the sense relations of collocation, hyponymy, and meronymy. , Thesis (MEd) -- Education, Education, 2021
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Date Issued: 2021-04

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