Biomechanical investigations of coordination during initial acceleration in highly trained to world class sprinters

Thesis (Sport Science (Biomechanics))--University of Pretoria, 2023.Initial sprint acceleration is a complex and dynamic skill, requiring the application of large forces to propel the body forwards. Effective force application is achieved through the use of joint and segment rotations in an organised and inter-related manner. While many of the isolated angular kinematic features associated with effective external force profiles are established, little is currently known about the relationships that exist between the key segments during the first steps of acceleration, i.e., the coordination of movement between functionally related elements. Through a series of three studies, this thesis explores inter- and intra-limb coordination during initial acceleration in sprinters ranging from highly trained to world class level, to enhance the understanding of sprint acceleration technique and performance. The first study provided a detailed description and quantification of inter-limb thigh-thigh, intra-limb shank-foot, and trunk-shank coordination during the first four steps of acceleration, and investigated changes in coordination between steps. Specific coordination features were identified and between-individual variation in coordination patterns in preparation for, or response to, the major transitions in the step cycle, i.e., touchdown and toe-off, were observed. Additionally, step-to-step changes in coordination and angular kinematics were identified, showing clearly differentiated coordination in step 1 compared to later steps. The second study utilised a novel application of hierarchical cluster analysis to vector coding data in order to identify and characterise sub-groups of sprinters with similar thigh-thigh and shank-foot coordination patterns, and subsequently explored discrete kinematic and performance differences between sub-groups. Three sub-groups were identified in step 1 and two sub-groups over steps 2-4. Sub-groups tended to be differentiated by differences in thigh-thigh coordination at the beginning and end of the step, and shank-foot coordination during flight as well as during ankle dorsiflexion in early stance. Combining sub-groups from step 1 and steps 2-4 to describe entire initial acceleration strategies, cluster combinations identified coordination approaches more likely to be associated with higher level sprinters and better performance. In the final investigation, relationships between coordination and lower body strength were evaluated in the context of dynamical systems theory, and the interaction of these two factors with regard to acceleration performance was explored. Several correlations existed between measures of lower body strength and features of thigh-thigh and shank-foot coordination, while multiple regression analysis suggested the presence of interaction effects between coordination and tests associated with lower body power in relation to performance. Thus, lower body power appeared to influence the relationships between coordination features and performance, such that the effectiveness of particular coordination patterns varied depending the lower body power of the athlete. The work included in this thesis provides a basis for understanding coordination during initial sprint acceleration, and includes several novel and exploratory approaches to investigating these questions which provides relevant information for practitioners and coaches interested in exploring the organisation of the body and coordination of segments during initial acceleration. Moreover, this work facilitate the generation of new hypotheses and encourages new directions in future research.PhysiologyPhD Sport Science (Biomechanics)UnrestrictedFaculty of Health Science

Analysis of the backpack loading efects on the human gait

Gait is a simple activity of daily life and one of the main abilities of the human being. Often during leisure, labour and sports activities, loads are carried over (e.g. backpack) during gait. These circumstantial loads can generate instability and increase biomechanicalstress over the human tissues and systems, especially on the locomotor, balance and postural regulation systems. According to Wearing (2006), subjects that carry a transitory or intermittent load will be able to find relatively efficient solutions to compensate its effects.info:eu-repo/semantics/publishedVersio

Sports Performance and Health

Sports performance is primarily associated with elite sport, however, recreational athletes are increasingly attempting to emulate elite athletes. Performance optimization is distinctly multidisciplinary. Optimized training concepts and the use of state-of-the-art technologies are crucial for improving performance. However, sports performance enhancement is in constant conflict with the protection of athletes’ health. Notwithstanding the known positive effects of physical activity on health, the prevention and management of sports injuries remain major challenges to be addressed. Accordingly, this Special Issue on "Sports Performance and Health" consists of 17 original research papers, one review paper, and one commentary, and covers a wide range of topics related to fatigue, movement asymmetries, optimization of sports performance by training, technique, and/or tactics enhancements, prevention and management of sports injuries, optimization of sports equipment to increase performance and/or decrease the risk of injury, and innovations for sports performance, health, and load monitoring. As this Special Issue offers several new insights and multidisciplinary perspectives on sports performance and health, readers from around the world who work in these areas are expected to benefit from this Special Issue collection

Training Load and Performance Monitoring, Recovery, Wellbeing, Illness and Injury Prevention

This book represents the efforts of different authors to analyze and provide solid evidence that supports training regulations based on monitoring strategies. This Special Issue includes original articles with some diversity, i.e., considering that different age groups, competitive levels, expertise, and conditions were researched regarding the main topics of training load and performance monitoring, recovery, wellbeing, and illness and injury prevention. Psychophysiological aspects were considered, as were locomotor and mechanical demands and tactical responses. The myriad outcomes analyzed present the reader with an overview of the state of the art and possible new directions for future research. In this book, readers will be also able to find systematic reviews about the key topics

Pushing for Gold On Force Application in Bobsleigh and Cycling

In many sports, performance is governed by an athlete’s ability to produce force paired with a given movement velocity and, thereby, generate power. The 4-man bobsled push start is an event that requires team effort, and its goal is to maximize sled velocity in the shortest possible time. Fractions of a second can decide the outcome of a race, and off-ice tests designed to assess strength and speed are used to identify the athletes that will perform best. However, the actual contributions of the team members during the push start on ice have not been measured. The objective of the first project in this thesis was to better understand the push contributions of the four athletes in a 4-man team by analyzing the components of the push start. A 4-man bobsled was instrumented to record both sled velocity and 2D push forces as applied to the sled by the athletes during the push start. Push force was observed to decrease quickly once the sled picked up speed, and the execution of the loading was discovered to be a crucial component of the push start that can affect overall performance. In project 2, a prowler sled was instrumented to measure sled velocity and push force in an off-ice push force-velocity test to be used as a training and assessment tool in bobsleigh athletes. Greater force results in greater power output – if the force is applied the right way. In project 3 we studied force effectiveness in cycling, where only pedal force directed perpendicular to the crank is effective i.e., results in propulsion, while forces parallel to the crank have been considered wasted. In our study, we aimed to determine the impact of constrained pedal force direction on force output. Constraining static pedal force to be perpendicular to the crank only was counterproductive and resulted in significantly reduced force magnitude. In summary, this thesis work contributes to the applied study of power output in sports, with instrumented devices aiding the study of force and power output in athletes, novel data, and the proposal for a new training method

Epidemiology of Injury in English Women's Super league Football: A Cohort Study

INTRODUCTION: The epidemiology of injury in male professional football has been well documented (Ekstrand, Hägglund, & Waldén, 2011) and used as a basis to understand injury trends for a number of years. The prevalence and incidence of injuries occurring in womens super league football is unknown. The aim of this study is to estimate the prevalence and incidence of injury in an English Super League Women’s Football squad. METHODS: Following ethical approval from Leeds Beckett University, players (n = 25) signed to a Women’s Super League Football club provided written informed consent to complete a self-administered injury survey. Measures of exposure, injury and performance over a 12-month period was gathered. Participants were classified as injured if they reported a football injury that required medical attention or withdrawal from participation for one day or more. Injuries were categorised as either traumatic or overuse and whether the injury was a new injury and/or re-injury of the same anatomical site RESULTS: 43 injuries, including re-injury were reported by the 25 participants providing a clinical incidence of 1.72 injuries per player. Total incidence of injury was 10.8/1000 h (95% CI: 7.5 to 14.03). Participants were at higher risk of injury during a match compared with training (32.4 (95% CI: 15.6 to 48.4) vs 8.0 (95% CI: 5.0 to 10.85)/1000 hours, p 28 days) of which there were three non-contact anterior cruciate ligament (ACL) injuries. The epidemiological incidence proportion was 0.80 (95% CI: 0.64 to 0.95) and the average probability that any player on this team will sustain at least one injury was 80.0% (95% CI: 64.3% to 95.6%) CONCLUSION: This is the first report capturing exposure and injury incidence by anatomical site from a cohort of English players and is comparable to that found in Europe (6.3/1000 h (95% CI 5.4 to 7.36) Larruskain et al 2017). The number of ACL injuries highlights a potential injury burden for a squad of this size. Multi-site prospective investigations into the incidence and prevalence of injury in women’s football are require