BACK STRESS AND ASSISTANCE EXERCISES IN WEIGHTLIFTING

The purpose of this study was to test the suitability of selected assistance exercises to strengthen the low back for the Olympic lifts in high level weightlifters. Four subjects were filmed by a five-camera Motion Analysis system operating at 120Hz completing both of the Olympic lifts (Snatch and Clean) and four assistance exercises (Romanian Oeadlift (ROL), Bent-over Row (BOR), Clean Pull Oeadlift (CPO), and Good Morning (GM)). Peak Erector Spinae Force (ESF) and L5/S1 compressive and shear force (L5/S1 CF and L5/S1 SF respectively) were calculated via a top-down inverse dynamics model. Comparisons between the lifts were made using a one-way ANOVA with repeated measures. It was found that the CPO produced higher ESF than the Snatch but this exercise also produced very high L5/S 1 CF and L5/S1 SF. The Clean also displayed a higher ESF than the Snatch. When normalising the data to bar weight, the BOR and GM was shown to potentially produce high ESF but coaches should consider the possibility for these exercises to produce low back injury

Stochastic Gene Expression in a Lentiviral Positive Feedback Loop: HIV-1 Tat Fluctuations Drive Phenotypic Diversity

Stochastic gene expression has been implicated in a variety of cellular processes, including cell differentiation and disease. In this issue of Cell, Weinberger et al. (2005) take an integrated computational-experimental approach to study the Tat transactivation feedback loop in HIV-1 and show that fluctuations in a key regulator, Tat, can result in a phenotypic bifurcation. This phenomenon is observed in an isogenic population where individual cells display two distinct expression states corresponding to latent and productive infection by HIV-1. These findings demonstrate the importance of stochastic gene expression in molecular "decision-making."Comment: Supplemental data available as q-bio.MN/060800

PEAK POWER OUTPUT IN THE IPOWER CLEAN -THE INFLUENCE OF RELATIVE STRENGTH

The aim of this study was to determine whether athletes of higher relative strength maximise their power output at higher percentages of their 1RM in the power clean. Twenty-nine male athletes (power clean 1 RM = 99.2 ± 18.9 kg) performed two power cleans at 10% increments from 50% to 100% of 1 RM. Bar displacement was collected by a Ballistic Measurement System (BMS) and power output was calculated using system mass (SM) and bar mass (BM) methods. Optimal loads were 50% and' 90% for the SM and BM methods respectively. However, a limitation of the stUdy was that loads below 50% of 1RM were not examined. Relative strength was not related to percentage of 1 RM at which maximal power output was achieved

A comparison of methods to calculate the optimal load for maximal power output in the power clean

The aim of this study was to compare three calculation methods to determine the load that maximises power output in the power clean. Five male athletes (height=179.8 10.5cms, weight 91 .8 8.8kg, power dean 1RM = 117.0 20.5kg) performed two per cleans at 10% increments from 50% to 100% of 1RM. Bar displacement data was collected using a Ballistic Measurement System (BMS) and vertical ground reaction force (VGRF) data was measured by a Kistler 9287B Force Plate. Power output was calculated for BMS (system mass), BMS (bar mass) and VGRF/BMS system mass. Optimal load was determined to be 70% for the BMS (system mass) and VGRF BMS (system mass) methods and 90% for the BMS (bar mass) method. Sports scientists should be aware of the technical issues underlying these findings due to the practical ramifications for athlete testing and training.<br /

A COMPARISON OF METHODS TO CALCULATE THE OPTIMAL LOAD FOR MAXIMAL POWER OUTPUT IN THE POWER CLEAN

The aim of this study was to compare three calculation methods to determine the load that maximises power output in the power clean. Five male athletes (height=179.8 10.5cms, weight 91.8 8.8kg. power clean 1RM = 117.0 20.5kg) performed two power cleans at 10% increments from 50% to 100% of 1RM. Bar displacement data was collected using a Ballistic Measurement System (BMS) and vertical ground reaction lorce (VGRF) data was measured by a Kistler 9287B Force Plate. Power output was calculated for BMS (system mass), BMS (bar mass) and VGRF/BMS system mass. Optimal load was determined to be 70% for the BMS (system mass) and VGRF 8MS (system mass) methods and 90% for the BM3 (bar mass) method. Sports scientists should be aware of the technical issues underlying these findings due to the practical ramifications for athlete testing and training

A Biometric Identity Based Signature Scheme

We describe an identity based signature scheme that uses biometric information to construct the public key. Such a scheme would be beneficial in a legal dispute over whether a contract had been signed or not by a user. A biometric reading provided by the alleged signer would be enough to verify the signature. We make use of Fuzzy extractors to generate a key string from a biometric measurement. We use this biometric based key string and an elliptic curve point embedding technique to create the public key and corresponding private key. We then make use of a pairing based signature scheme to perform signing and verification with these keys. We describe a possible attack on this system and suggest ways to combat it. Finally we describe how such a biometric signature scheme can be developed by reusing existing components in our Java Identity Based Encryption implementation. The design allows traditional as well as biometric identity based signatures

Supplemental Data: Stochastic Gene Expression in a Lentiviral Positive Feedback Loop: HIV-1 Tat Fluctuations Drive Phenotypic Diversity

Supplemental data for "Stochastic Gene Expression in a Lentiviral Positive Feedback Loop: HIV-1 Tat Fluctuations Drive Phenotypic Diversity" [q-bio.MN/0608002, Cell. 2005 Jul 29;122(2):169-82].Comment: Supplemental data for q-bio.MN/060800

UK: racial violence and the night-time economy

This article examines fifty-five racist attacks over a six-month period in the UK’s night-time economy, showing the risks faced by members of the public and workers at taxi firms, takeaways, convenience stores and service stations. It argues that flexible and highly casualised labour conditions exacerbate the risk of racial violence

Emergence of three general practitioner contracting-in models in South Africa: a qualitative multi-case study

Background: The general practitioner contracting initiative (GPCI) is a health systems strengthening initiative piloted in the first phase of national health insurance (NHI) implementation in South Africa as it progresses towards universal health coverage (UHC). GPCI aimed to address the shortage of doctors in the public sector by contracting-in private sector general practitioners (GPs) to render services in public primary health care clinics. This paper explores the early inception and emergence of the GPCI. It describes three models of contracting-in that emerged and interrogates key factors influencing their evolution. Methods: This qualitative multi-case study draws on three cases. Data collection comprised document review, key informant interviews and focus group discussions with national, provincial and district managers as well as GPs (n = 68). Walt and Gilson’s health policy analysis triangle and Liu’s conceptual framework on contracting-out were used to explore the policy content, process, actors and contractual arrangements involved. Results: Three models of contracting-in emerged, based on the type of purchaser: a centralized-purchaser model, a decentralized-purchaser model and a contracted-purchaser model. These models are funded from a single central source but have varying levels of involvement of national, provincial and district managers. Funds are channelled from purchaser to provider in slightly different ways. Contract formality differed slightly by model and was found to be influenced by context and type of purchaser. Conceptualization of the GPCI was primarily a nationally-driven process in a context of high-level political will to address inequity through NHI implementation. Emergence of the models was influenced by three main factors, flexibility in the piloting process, managerial capacity and financial management capacity. Conclusion: The GPCI models were iterations of the centralized-purchaser model. Emergence of the other models was strongly influenced by purchaser capacity to manage contracts, payments and recruitment processes. Findings from the decentralized-purchaser model show importance of local context, provincial capacity and experience on influencing evolution of the models. Whilst contract characteristics need to be well defined, allowing for adaptability to the local context and capacity is critical. Purchaser capacity, existing systems and institutional knowledge and experience in contracting and financial management should be considered before adopting a decentralized implementation approach

Impulsivity and Rapid Decision-Making for Reward

Impulsivity is a feature of many brain disorders. Although often defined as the predisposition to act with an inadequate degree of deliberation, forethought, or control, it has proven difficult to measure. This may in part be due to the fact that it is a multifaceted construct, with impulsive decisions potentially arising as a result of a number of underlying mechanisms. Indeed, a “functional” degree of impulsivity may even promote effective behavior in healthy participants in a way that can be advantageous under certain circumstances. Although many tasks have been developed to study impulsivity, few examine decisions made rapidly, for time-sensitive rewards. In the current study we examine behavior in 59 adults on a manual “Traffic Light” task which requires participants to take risks under time pressure, if they are to maximize reward. We show that behavioral variables that index rapid anticipatory responding in this paradigm are correlated with one, specific self-report measure of impulsivity: “lack of premeditation” on the UPPS Impulsive Behavior Scale. Participants who scored more highly on this subscale performed better on the task. Moreover, anticipatory behavior reduced significantly with age (18–79 years), an effect that continued to be upheld after correction for potential age differences in the ability to judge the timing of responses. Based on these findings, we argue that the Traffic Light task provides a parametric method to study one aspect of impulsivity in health and disease: namely, rapid decision-making in pursuit of risky, time-sensitive rewards