COMPARISON OF FORCE CURVES BETWEEN ON-WATER SINGLE SCULL ROWING AND THE ROWPERFECT ERGOMETER

The purpose of this study was to compare the RowPerfect ergometer to single scull rowing in order to validate its use in rowing training and crew selection. Eight national-level rowers were tested over three sets of 500 m, at stroke rates of 24, 26 and 28, on both the RowPerfect ergometer and on-water in a single scull. Blade force and oar angle were measured on-water while force and stroke length were measured on the ergometer. Both force and angle/length were normalised for comparison between the two forms of rowing. Co-efficient of multiple determination revealed high consistency levels for the 5 representative normalised stokes of each subject. Cross-correlation demonstrated high correlations between the force curves of the ergometer and on-water sculling. Thus, the results indicate that the RowPerfect ergometer successfully simulates on-water sculling

THE CONSISTENCY OF FORCE AND MOVEMENT VARIABLES AS AN INDICATOR OF ROWING PERFORMANCE

A portable biomechanical collection system was used to test fourteen male, coxless pair rowing crews under simulated race speeds. The data was used to examine if the consistency of 8 biomechanical variables, calculated using a modified Coefficient of Variation (CoV), were related to the overall performance, in terms of velocity, of the crews. It was found that 6 of the variables demonstrated a significant correlation to overall boat speed, with the consistency of Normal Gate Force (r=0.737), Handle Velocity (r=0.758) and Trunk Velocity (r=.757) showing very strong correlation. It was concluded that while not imperative to the outcome, consistency of force application and movement patterns may be important in rowing performance

A COMPARISON OF UNDERWATER GLIDING AND KICKING TECHNIQUES

Net forces created when towing swimmers through water were examined for gliding and undelwater kicking. Sixteen experienced male swimmers of similar body shape were towed through water via a motorised winch and pulley system. A load cell measured net force (propulsive force - drag force) at velocities of 1.6, 1.9, 2.2, 2.5 and 3.1 ms-', respectively. At each velocity swimmers performed a prone streamline glide; lateral streamline glide; prone freestyle kick; prone dolphin kick; and lateral dolphin kick. A 2- way repeated measures ANOVA revealed significant differences between the gliding and kicking conditions at different velocities. Results suggest that there is an optimal velocity at which to begin undelwater kicking in order to prevent energy loss from excessive active drag

MORPHOLOGY AND HYDRODYNAMIC RESISTANCE IN YOUNG SWIMMERS

Morphology and hydrodynamic drag were measured of 6 males and 6 females, from each of the 9, 11 and 13 yr age groups. Net forces were examined when towing swimmers while prone streamlined gliding and flutter kicking at 1.3 to 2.5 ms-1. The passive drag force at 1.9, 2.2 and 2.5 ms-1 increased with age and anthropometry, but no changes were found at 1.3 and 1.6 ms-1. Stepwise regression revealed passive drag best predicted net active drag at velocities of 1.3, 1.9, 2.2 and 2.5 ms-1. Results supported the Froude number theory that increased height will reduce wave-making drag

CXCR4 expression heterogeneity in neuroblastoma cells due to ligand-independent regulation

<p>Abstract</p> <p>Background</p> <p>CXCR4, the receptor for the chemokine stromal-derived factor 1 (SDF-1), has been shown to mediate many of the processes essential for cancer progression such as tumor cell proliferation, metastasis, and angiogenesis. To understand the role of CXCR4 in the biology of neuroblastoma, a disease that presents with wide spread metastases in over 50% of patients, we screened ten patient derived-neuroblastoma cell-lines for basal CXCR4 expression and sought to identify characteristics that correlate with tumor cell phenotype.</p> <p>Results</p> <p>All cell lines expressed <it>CXCR4 </it>mRNA at variable levels, that correlated well with three distinct classes of CXCR4 surface expression (low, moderate, or high) as defined by flow cytometry. Analysis of the kinetics of CXCR4 surface expression on moderate and high expressing cell lines showed a time-dependent down-regulation of the receptor that directly correlated with cell confluency, and was independent of SDF1. Cell lysates showed the presence of multiple CXCR4 isoforms with three major species of approximately 87, 67 and 55 kDa associating with high surface expression, and two distinct species of 45 and 38 kDa correlating with low to null surface expression. Western blot analysis of CXCR4 immunoprecipitates showed that the 87 and 67 kDa forms were ubiquitinated, while the others were not. Finally, treatment of cells with a proteasome inhibitor resulted in down regulation of CXCR4 surface expression.</p> <p>Conclusions</p> <p>Taken together, these data show that regulation of CXCR4 surface expression in neuroblastoma cells can occur independently of SDF-1 contribution arguing against an autocrine mechanism. Additionally these data suggest that post-translational modifications of CXCR4, in part through direct ubiquitination, can influence trafficking of CXCR4 to the surface of neuroblastoma cells in a ligand-independent manner.</p

OPTIMISING KINETICS IN THE FREESTYLE FLIP TURN PUSH-OFF

INTRODUCTION: Turning technique is an important component in swimming performance with turn times positively correlating with final event time. However, little is known about the mechanics of an effective turn. This study sought to provide an exploratory analysis of how various kinetic and hydrodynamic variables during wall push-off are related to the wall exit velocity. METHODS: Thirty experienced male swimmers with body types of within one SD of the mean for selected anthropometric parameters reported for elite male adult swimmers (Mazza et al., 1994) were recruited for the study. During three freestyle flip turns, selected kinetic, hydrodynamic and kinematic variables of the wall pushoff were recorded. The wall push-off phase was measured from the point of maximum knee flexion during wall contact until the feet left the wall. Kinetics were recorded via a 2D vertically mounted forceplate which recorded peak push-off force and total impulse. The acceleration of each swimmer’s centre of gravity (CG) and wall exit velocity of the CG were calculated from underwater videography. Hydrodynamic peak drag force and drag impulse were calculated from the kinetic and kinematic data using a derivative of Newton’s second law. RESULTS: A stepwise regression was performed with wall exit velocity as the criterion variable and push-off time, peak propulsive force, total propulsive impulse, peak drag force, and total drag impulse as the independent variables. The stepwise regression yielded peak drag force, peak propulsive force and push-off time in the equation, with beta values indicating that the peak drag force carried the highest weighting of the three variables. CONCLUSIONS: The results of the stepwise regression indicated that an optimal combination of a low peak drag force, high peak propulsive force and increased wall time produced the fastest wall exit velocity. The inclusion of the peak drag force in the regression equation as the most important predictor of wall exit velocity highlights the importance of drag in turning technique. Factors such as very high push-off forces and exaggerated movements during wall push-off may lead to higher peak drag forces which, in turn, could be detrimental to the overall turning performance

Unsteady flow phenomena in human undulatory swimming: a numerical approach

The undulatory underwater sequence is one of the most important phases in competitive swimming. An understanding of the recurrent vortex dynamics around the human body and their generation could therefore be used to improve swimming techniques. In order to produce a dynamic model, we applied human joint kinematics to three-dimensional (3D) body scans of a female swimmer. The flow around this dynamic model was then calculated using computational fluid dynamics with the aid of moving 3D meshes. Evaluation of the numerical results delivered by the various motion cycles identified characteristic vortex structures for each of the cycles, which exhibited increasing intensity and drag influence. At maximum thrust, drag forces appear to be 12 times higher than those of a passive gliding swimmer. As far as we know, this is the first disclosure of vortex rings merging into vortex tubes in the wake after vortex recapturing. All unsteady structures were visualized using a modified Q-criterion also incorporated into our methods. At the very least, our approach is likely to be suited to further studies examining swimmers engaging in undulatory swimming during training or competition

Understanding the Effects of Training on Underwater Undulatory Swimming Performance and Kinematics

In swimming, the underwater phase after the start and turn comprises gliding and dolphin kicking, with the latter also known as underwater undulatory swimming (UUS). Swimming performance is highly dependent on the underwater phase; therefore, understanding the training effects in UUS and underwater gliding can be critical for swimmers and coaches. Further, the development of technique in young swimmers can lead to exponential benefits in an athlete’s career. This study aimed to evaluate the effects of a training protocol on UUS and underwater gliding performance and kinematics in young swimmers. Seventeen age group swimmers (boys = 10, girls = 7) performed maximal UUS and underwater gliding efforts before and after a seven-week training protocol. Time to reach 10 m; intra-cyclic mean, peak, and minimum velocities; and gliding performance improved significantly after the training protocol. The UUS performance improvement was mostly produced by an improvement of the upbeat execution, together with a likely reduction of swimmers’ hydrodynamic drag. Despite the changes in UUS and gliding, performance was also likely influenced by growth. The findings from this study highlight kinematic variables that can be used to understand and quantify changes in UUS and gliding performance

The "Petechiae in children" (PiC) study: Evaluating potential clinical decision rules for the management of feverish children with non-blanching rashes, including the role of point of care testing for Procalcitonin &amp; Neisseria meningitidis DNA - a stu

© 2018 The Author(s). Background: Children commonly present to Emergency Departments (ED) with a non-blanching rash in the context of a feverish illness. While most have a self-limiting viral illness, this combination of features potentially represents invasive serious bacterial infection, including meningococcal septicaemia. A paucity of definitive diagnostic testing creates diagnostic uncertainty for clinicians; a safe approach mandates children without invasive disease are often admitted and treated with broad-spectrum antibiotics. Conversely, a cohort of children still experience significant mortality and morbidity due to late diagnosis. Current management is based on evidence which predates (i) the introduction of meningococcal B and C vaccines and (ii) availability of point of care testing (POCT) for procalcitonin (PCT) and Neisseria meningitidis DNA. Methods: This PiC study is a prospective diagnostic accuracy study evaluating (i) rapid POCT for PCT and N. meningitidis DNA and (ii) performance of existing clinical practice guidelines (CPG) for feverish children with non-blanching rash. All children presenting to the ED with a history of fever and non-blanching rash are eligible. Children are managed as normal, with detailed prospective collection of data pertinent to CPGs, and a throat swab and blood used for rapid POCT. The study is running over 2years and aims to recruit 300 children. Primary objective: Report on the diagnostic accuracy of POCT for (i) N. meningitidis DNA and (ii) PCT in the diagnosis of early MD Discussion: The PiC study will provide important information for policy makers regarding the value of POCT and on the utility and cost of emerging diagnostic strategies. The study will also identify which elements of existing CPGs may merit inclusion in any future study to derive clinical decision rules for this population

Kohler's disease: An unusual cause for a limping child

Kohler's disease: an unusual cause for a limping chil