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A biomechanical model of the glenohumeral joint has been developed to investigate muscle and joint loading during real life three-dimensional activities. Based on a rigid body mechanics approach, the model incorporates algorithms to correct for curved muscle paths and bone geometry, providing realistic muscle orientation over a wide range of limb positions. An optimization routine has been incorporated, minimizing overall maximum muscle stress in the 26 individual muscle elements considered. The model utilizes anatomical muscle and bone data, subject anthropometric data, kinematics measured using a 6 camera Vicon motion analysis system and hand loading measured using a force-plate and mobile six-component strain gauged force transducer developed for this project. Model stability and sensitivity to input data uncertainties have been investigated. Data used for this was actual subject activity data. Random uncertainties of a known statistical distribution were generated using a Monte Carlo data perturbation technique and superimposed on the subject data. No model instability or unacceptable error magnification was demonstrated in this investigation. A study of real life three-dimensional activities has been conducted using five male subjects. Normalized, averaged muscle and joint forces were calculated for each activity. Using the same five subjects, electromyographic (EMG) muscle activation was measured for the same five activities. Both surface and intra-muscular fine wire electrode techniques were used. Eight muscles including infraspinatus, subscapularis and supraspinatus were instrumented. The resulting EMG data was normalized and averaged for each activity. Muscle activation appears in good agreement with published EMG and our own EMG study. Overall joint compressive and shear forces of up to 7 and 2 times body weight respectively have been calculated. Results of the study indicate glenohumeral joint forces for athletic activities can be as high as 7 times those forces previously predicted in other studies for simple abduction and flexion.

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No description available.

Research report in partial fulfillment for the degree of MSc (Med), Population Based Field Epidemiology, University of the Witwatersrand / Background Worldwide, injuries are ranked among the leading causes of death and disability, killing over 5 million people and injuring over 50 million others globally. Approximately 90% of these deaths occur in developing countries. The burden and pattern of injuries in low-income countries are poorly known and not well studied. Few studies have been conducted on injury mortality and therefore this study can add to the scientific literature. Analyzing injury mortality in rural Tanzania can assist African countries to develop intervention programmes and policy reform to reduce the burden caused by injuries. Objectives The objective of this study was to identify the risk factors and trend in injury mortality in the Rufiji Demographic Surveillance Area in rural Tanzania from 2002-2007. Specifically, the study would identify and describe the types and trends in injury mortality, calculate the crude death rates of injury mortality by gender, SES and age groups, describe the risks factors associated with injury mortality, and measure association between the risk factors and injury mortality. Methods Rufiji HDSS data used included people aged 1 year and older from 2002-2007. Verbal Autopsy data was used to determine the causes of death which was based on the tenth revision of the International Classification of Diseases (ICD 10) recommended by WHO. Injury Crude death rates (ICDR) were calculated by dividing number of deaths in each year by person years observed and multiplying by 100,000. Principal Component Analysis (PCA) was used to construct household wealth index using household characteristics and assets ownership. Also trend test analysis was done to assess a linear relationship in the injury mortality rates across the six year period. Poisson regression was used to investigate v association between risk factors and injury mortality and all tests for significant associations were based on p-values at 5% significance level and a 95% confidence interval. Results The overall injury crude mortality rate was 33.4 per 100,000 PYO. Injuries contributed 4% of total mortality burden with statistical significant association between gender, age and occupation. Mortality rate was higher for males [Adjusted IRR=3.04, P=0.001, 95% CI (2.22 - 4.17)]. The elderly (65+) were 2.8 times more likely to die from injuries compared to children [Adjusted IRR=2.83, P=0.048, 95% CI (1.01 - 7.93)]. The unemployed, casual workers, the retired, and farmers all had an increased risk of dying from injuries compared to students (P<0.005). Most injury deaths were due to road traffic accidents (28%), unspecified external injuries (20%), drowning (16%), burns (9%), accidental poisoning (8%), homicidal (8%) and animal attack (5%). Conclusion The contribution of injury to mortality burden in the Rufiji Demographic Surveillance Area was relatively low. However, there is the need to institute measures that would help prevent injuries. Life saving interventions such as road safety education, regular road maintenance, rapid response to accidents, use of life jackets for fishermen and recreational swimmers are very necessary in preventing injuries. Also, proper fishing practices should be imparted to the populace as precautionary measures to reduce the burden of injury mortality.

This thesis investigates the epidemiology of lifestyle behaviours and training injuries among British Army infantry recruits. In Study 1, the Military Pre-training Questionnaire (MPQ) was developed to assess multiple risk factors for injury (smoking; alcohol consumption; physical activity; diet; and injury history). Its feasibility and test-retest reliability was demonstrated in a representative sample (n = 58) with no evidence of systematic bias between administrations. The MPQ was subsequently completed by a large cohort of infantry recruits before commencing initial training (n = 1,960). This enabled its validity to be assessed in Study 2, which revealed that a simple, single-item measure of pre-training physical activity was a strong predictor of initial physical fitness levels and likely training outcomes. In Study 3, cross-sectional analyses of MPQ responses enabled the prevalence, co-occurrence and clustering of unhealthy lifestyle behaviours to be assessed. Although physically active, the majority of recruits entering infantry training smoked, drank hazardously and had low fruit and vegetable consumption. Six percent of recruits reported no unhealthy lifestyle behaviours, 20% reported one, 35% reported two, 31% reported three and 8% reported all four. Paired combinations of unhealthy behaviours were strongly associated, particularly smoking/drinking, smoking/inactivity and diet/inactivity. Finally, in Study 4, a high incidence of overuse injuries in infantry recruits was observed using a prospective study design. Recruits with lower pre-training fitness levels, low body mass and past injuries were exposed to a higher risk of sustaining a training injury, while there was no evidence to suggest that engaging in unhealthy lifestyle behaviours increased injury risk. Collectively, the four studies have enabled, for the first time, a comprehensive analysis of lifestyle behaviours and training injuries among British Army infantry recruits. The findings have important implications for military health improvement and injury prevention strategies.

Hamstring injury is common in sprinting sports and injury recurrence remains a major concern. The aim of this thesis is to explore the biomechanical characteristics of athletes following sprint related hamstring injury. We conducted 1) An examination of already published research on biomechanical deficits following hamstring injury in athletes who had returned to sport by means of a systematic review and meta-analysis; 2) A detailed examination of sprinting following hamstring injury in athletes who had returned to sport muscle activity using 3D motion capture and surface EMG; 3) An examination of high intensity eccentric loading performance in previously injured athletes using low density, high surface area surface EMG and measures of force; 4) An analysis of hamstring muscle recovery until return to sport following hamstring injury using low density, high surface area surface EMG and measures of force via case reports in two elite athletes. Previous research indicates that athletes who had returned to sport following hamstring injury continue to display deficits in force production, especially during slow eccentric contractions. The observational studies indicate that athletes run with significantly asymmetric movements about the pelvis and hip that would place their hamstrings under increased length during the terminal swing phase of sprinting. Furthermore, significant alterations in late swing EMG ratios suggest relatively reduced activity in the previously injured biceps femoris. Spatial activation of the hamstring appears altered in previously injured athletes, with reduced relative activation of the proximal muscle and reduced median frequency values in the medial muscle compared to control limbs. Asymmetries in activation patterns are also noted in the pre-return to sport phase. Previous hamstring injury is associated with significant alterations in force production, movement symmetry and muscle activation patterns following return to sport highlighting the complexity of this injury and the need for advanced rehabilitation screening approaches.

Background: Myocardial injury affects up to one in three patients undergoing non-cardiac surgery. However, very little is known about the underlying pathophysiology. In the general population, patients with elevated resting heart rate are at increased risk of cardiac events, mortality, heart failure and autonomic dysfunction, while hypertension is a well described risk factor for cardiovascular disease. I hypothesised that common abnormalities of heart rate or blood pressure were associated with myocardial injury after non-cardiac surgery. Methods: This thesis comprises a series of secondary analyses of data from five prospective multi-centre epidemiological studies of surgical patients. The main outcome of interest was myocardial injury, defined using objective measurement of cardiac troponin. I used logistic regression analysis to test for association between exposures and outcomes. Results: In a large international cohort, patients with high preoperative heart rate had increased risk of myocardial injury and patients with very low preoperative heart rate had reduced risk of myocardial injury. Patients with elevated preoperative pulse pressure had increased risk of myocardial injury, independent of existing hypertension or systolic blood pressure. High heart rate, or high or low systolic blood pressure during surgery, was associated with increased risk of myocardial injury. In a separate study, elevated preoperative heart rate was associated with cardiopulmonary and autonomic dysfunction, and reduced left ventricular stroke volume, suggestive of heart failure. Finally, autonomic dysfunction, identified using cardiopulmonary exercise testing, was associated with elevated preoperative heart rate, elevated plasma NT-Pro-BNP (indicative of heart failure) and postoperative myocardial injury. Conclusions: Elevated preoperative heart rate, autonomic dysfunction and subclinical heart failure may be part of a common phenotype associated with perioperative myocardial injury. Further research is needed to characterise the pathological processes responsible for myocardial injury, and to identify potential therapeutic targets.