Biomechanical factors associated with the risk of knee injury when landing from a jump

Objectives. To systematically assess the literature investigating biomechanical knee injury risk factors when an individual lands from a jump. Data sources. Four electronic databases were searched for peer-reviewed English journals containing landing biomechanical studies published over 14 years (1990 - 2003). Study selection. Publications describing research into knee joint kinetics and/or kinematics when landing from a jump were included. A total of 26 eligible articles met the inclusion criteria. Data extraction. A review of the 26 eligible studies was undertaken to describe the key study components including the study aims, sample populations, measurement tools, measurement procedures and knee risk factors. Methodological quality was scored using the Crombie Checklist and PEDro Scale. Data synthesis. The methodological quality of the studies reviewed was fair. Information on risk factors was variable. One proposed risk factor, landing with the knee in a relatively more extended position, may increase injury risk. Validity was compromised when the landing action was isolated by studying drop-jumping instead of the whole landing task. Results of reviewed studies were potentially confounded by a number of factors. Conclusion. High-level evidence for biomechanical knee injury risk factors when landing from a jump is lacking and it is difficult to draw conclusions regarding knee injury risk factors when landing. However, the published research reviewed provides important information on injury causality and theories to direct future studies. Further research should be directed towards younger populations using valid testing protocols applicable to real life scenarios. South African Journal of Sports Medicine Vol. 18 (1) 2006: pp. 18-2

Soil resistivity : a limiting determinant to zero-sequence currents for grounded conductors in South African low voltage networks

Abstract: In this paper, the dependence of soil resistivity on the geological structure and meteorological conditions are discussed. The South African context of changing resistivity and its inevitable consequences on the behaviour of prospective zero-sequence currents in low-voltage distribution systems is highlighted. Therefore, field measurements of soil resistivity using the Wenner Array technique is conducted on expansive clay-based soil. The resulting zero-sequence current inherent to the soil conditions is also assessed. The results obtained indicated that the soil resistivity value of 488.74 Ω. m, which corresponds to the soil conditions at the time and measurement season, represents an increase of 62.91% of the standard limit value for expansive clays, and causes 37.14% decrease in the zero-sequence current likely to flow at the limit value of expansive clay’s resistivity

Proximal placement of lateral thigh skin markers reduces soft tissue artefact during normal gait using the Conventional Gait Model

A primary source of measurement error in gait analysis is soft tissue artefact. Hip and knee angle measurements, used regularly to guide clinical decisions, are particularly affected due to pervasive soft tissue on the femur. However, despite several studies of thigh marker artefact it remains unclear how lateral thigh marker height affects results using the popular Plug-in Gait model. We compared Plug-in Gait hip and knee joint angles for ten healthy subjects estimated using a proximal- and distal-third thigh marker placement and found significant differences. Relative to the distal marker, the proximal marker produced 37% less varus-valgus range and 50% less hip rotation range, suggesting that it produced less soft-tissue artefact in knee axis estimates. Knee flexion was also significantly affected due to knee centre displacement. Based on an analysis of the Plug-in Gait knee axis definition and two different numerical optimization of the thigh rotation offset parameter, we show that the proximal marker reduced sensitivity to soft-tissue artefact by decreasing collinearity between the points defining the femoral frontal plane and reducing anteroposterior movement between the knee and thigh markers. This study demonstrates that Plug-in Gait thigh marker height can have a considerable influence on outcomes used for clinical decision-making

A systematic review and appraisal of methods of developing and validating lifestyle cardiovascular disease risk factors questionnaires

Background: Well developed and validated lifestyle cardiovascular disease (CVD) risk factors  questionnaires is the key to obtaining accurate information to enable planning of CVD prevention program which is a necessity in developing countries. We conducted this review to assess methods and processes used for development and content validation of lifestyle CVD risk factors questionnaires and possibly  develop an evidence based guideline for development and content validation of lifestyle CVD risk factors questionnaires.Materials/methods: Relevant databases at the Stellenbosch University library were searched for  studies conducted between 2008 and 2012, in English language and among humans. Using the following databases; pubmed, cinahl, psyc info and proquest. Search terms used were CVD risk factors, questionnaires, smoking, alcohol, physical activity and diet.Results: Methods identified for development of lifestyle CVD risk factors were; review of literature either systematic or traditional, involvement of expert and /or target population using focus group   discussion/interview, clinical experience of authors and deductive reasoning of authors. For validation, methods used were; the involvement of expert panel, the use of target population and factor analysis.Conclusion: Combination of methods produces questionnaires with good content validity and other psychometric properties which we consider good.Keywords: systematic review, lifestyle cardiovascular disease, risk factors questionnaire

The prevalence of underweight, overweight and obesity in a multiracial group of urban adolescent schoolchildren in the Cape Metropole area of Cape Town

Objective: The objective was to determine the prevalence of underweight, overweight and obesity in high school learners in the Cape Town area.Design: A cross-sectional study was conducted.Setting: High schools in the Cape Metropole Area of the Western Cape.Subjects: A complex cluster sampling procedure was followed. Thirty-six students per school were selected from each randomly selected school. Thirteen- to 18-year-old pupils were eligible for inclusion.Outcome measures: Height and weight measurements.Results: The sample comprised 689 students. There were considerably  more underweight adolescent boys than adolescent girls (17.3% boys to 9.9% girls), and double the frequency of overweight adolescent girls than adolescent boys (7.7% girls to 3.5% boys). The 14-year-old boys had the highest prevalence of underweight (55.2%), and the 17-year-old girls the highest prevalence of overweight (22%). The highest prevalence of obesity was found in 15-year-old boys (11.1%), who also demonstrated a relatively high prevalence of underweight (30.2%).Conclusion: This study reported on a substantial percentage of underweight adolescents (27.1%). Noteworthy levels of overweight and obesity in  adolescent girls added to the substantial prevalence of underweight in adolescent boys. Africa has enough to contend with in respect of transmissible diseases, without additional lifestyle-based health burdens

PerfWeb: How to Violate Web Privacy with Hardware Performance Events

The browser history reveals highly sensitive information about users, such as financial status, health conditions, or political views. Private browsing modes and anonymity networks are consequently important tools to preserve the privacy not only of regular users but in particular of whistleblowers and dissidents. Yet, in this work we show how a malicious application can infer opened websites from Google Chrome in Incognito mode and from Tor Browser by exploiting hardware performance events (HPEs). In particular, we analyze the browsers' microarchitectural footprint with the help of advanced Machine Learning techniques: k-th Nearest Neighbors, Decision Trees, Support Vector Machines, and in contrast to previous literature also Convolutional Neural Networks. We profile 40 different websites, 30 of the top Alexa sites and 10 whistleblowing portals, on two machines featuring an Intel and an ARM processor. By monitoring retired instructions, cache accesses, and bus cycles for at most 5 seconds, we manage to classify the selected websites with a success rate of up to 86.3%. The results show that hardware performance events can clearly undermine the privacy of web users. We therefore propose mitigation strategies that impede our attacks and still allow legitimate use of HPEs

Biomechanical factors associated with the risk of knee injury when landing from a jump

Objectives. To systematically assess the literature investigating biomechanical knee injury risk factors when an individual lands from a jump. Data sources. Four electronic databases were searched for peer-reviewed English journals containing landing biomechanical studies published over 14 years (1990 - 2003). Study selection. Publications describing research into knee joint kinetics and/or kinematics when landing from a jump were included. A total of 26 eligible articles met the inclusion criteria. Data extraction. A review of the 26 eligible studies was undertaken to describe the key study components including the study aims, sample populations, measurement tools, measurement procedures and knee risk factors. Methodological quality was scored using the Crombie Checklist and PEDro Scale. Data synthesis. The methodological quality of the studies reviewed was fair. Information on risk factors was variable. One proposed risk factor, landing with the knee in a relatively more extended position, may increase injury risk. Validity was compromised when the landing action was isolated by studying drop-jumping instead of the whole landing task. Results of reviewed studies were potentially confounded by a number of factors. Conclusion. High-level evidence for biomechanical knee injury risk factors when landing from a jump is lacking and it is difficult to draw conclusions regarding knee injury risk factors when landing. However, the published research reviewed provides important information on injury causality and theories to direct future studies. Further research should be directed towards younger populations using valid testing protocols applicable to real life scenarios. South African Journal of Sports Medicine Vol. 18 (1) 2006: pp. 18-2

Ergonomic chair intervention : effect on chronic upper quadrant dysfunction, disability and productivity in female computer workers

CITATION: Hoeben, C. & Louw, Q. 2014. Ergonomic chair intervention : effect on chronic upper quadrant dysfunction, disability and productivity in female computer workers. South African Journal of Physiotherapy, 70(2):11-18, doi:10.4102/sajp.v70i2.32.The original publication is available at http://www.sajp.co.zaENGLISH SUMMARY : AIM: To compare the effect of two ergonomic chairs on upper quadrant musculoskeletal pain and tension, disability and productivity among female computer workers in the office workplace. METHODS: A series of two N=1 studies were conducted using the A-B-A-C-A design whereby an intervention ergonomic chair was compared to a less adjustable control ergonomic chair using visual analogue scales (VAS) for pain and muscle spasm, the Neck Disability Index and the Work Productivity and Activity Impairment questionnaire. The female participants were assessed over the four week phases as they performed high intensity visual display unit work. The results were compiled and tabulated. RESULTS: Both the control and intervention ergonomic chairs showed a reduction in both the mean and variance of pain and muscle spasm. The second participant also showed an increase in productivity with both chairs. CONCLUSION: The introduction of an ergonomic chair shows a reduction in VAS intensity and frequency for pain and muscle spasm, as well as a reduction in variance of the symptoms. Both chairs showed a similar reduction in symptoms, thus indicating almost equivalent benefit from the use of both ergonomic chairs.http://www.sajp.co.za/index.php/sajp/article/view/32Publisher's versio

Prevalence of musculoskeletal injuries among adolescent squash players in the Western Cape

Objective. To determine the prevalence of musculoskeletal injuries among adolescent squash players in the Western Cape. Design. A retrospective descriptive survey was conducted during the first week of May 2006. Three schools were randomly selected from a list of the top 10 schools in the Western Cape high school squash league of 2005, with 106 squash players aged 13 - 18 years participating in the study. Setting. Injury data were collected for 106 players at three schools randomly selected from a list of the top 10 schools in the Western Cape high school squash league of 2005. Interventions. An adapted structured self-administered questionnaire based on a previously validated musculoskeletal injury questionnaire was used to collect the data. Main outcome measures. The main variables investigated were prevalence, mechanism and injury site of musculoskeletal squash injuries. Results. Twenty-nine per cent of the players (N = 31) reported that they had sustained a squash injury in the 4 weeks prior to data collection. A total of 48 injuries were reported by the injured players. The most common injuries included those of the thigh (19%), shoulder (13%) and lower back (13%). Forty-two per cent of players reported no specific mechanism of injury, but experienced pain not associated with a traumatic injury only while playing squash. Conclusion. A relatively high prevalence of squash injuries was found. This preliminary study serves as a baseline for future research. Areas for further investigation were identified and this could lead to the implementation of preventive programmes and education to prevent injuries among adolescent squash players. South African Journal of Sports Medicine Vol. 19 (1) 2007: pp. 3-

Building capacity for development and implementation of clinical practice guidelines

Robust, reliable and transparent methodologies are necessary to ensure that clinical practice guidelines (CPGs) meet international criteria. In South Africa (SA) and other low- and middle-income countries, upskilling and training of individuals in the processes of CPG development is needed. Since de novo CPG development is time-consuming and expensive, new emerging CPG-development approaches (adopting, contextualising, adapting and updating existing good-quality CPGs) are potentially more appropriate for our context. These emerging CPG-development methods are either not included or sparsely covered in existing training opportunities. The SA Guidelines Excellence (SAGE) team has responded innovatively to the need for CPG training in SA. We have revised an existing SA course and developed an online, open-access CPG-development toolkit. This Guideline Toolkit is a comprehensive guideline resource designed to assist individuals who are interested in knowing how to develop CPGs. Findings from the SAGE project can now be implemented with this innovative CPG training programme. This level of CPG capacity development has the potential to influence CPG knowledge, development, practices and uptake by clinicians, managers, academics and policy-makers around the country