9,129 research outputs found
Comparisons between swing phase characteristics of race walkers and distance runners
The aim of this study was to analyze swing characteristics during race walking and to compare these with distance running. The rules of race walking demand that no visible flight time should occur and the stance leg must be straightened from initial contact to midstance. Previous research has not examined whether these rules also have an effect on swing and what consequences might arise. Ten male race walkers and ten male distance runners walked or ran respectively on an instrumented treadmill for 10 km with two in-dwelling force plates. Trials lasted 30 seconds and simultaneous 2D video data were recorded and digitized at 125 Hz. The moment of inertia of the thigh, shank, foot and whole lower limb was calculated using the parallel axis theorem. The distance runners were faster with longer strides, although cadence was not different. The race walkers had shorter swing times, longer contact times, and smaller maximum knee flexion angles (100° ± 6) than the distance runners (56° ± 6). The smaller knee flexion angles in race walkers meant they experienced greater swing leg moment of inertia than the distance runners but there were few associations in either group between knee flexion angle or moment of inertia with key performance parameters. Swing phase kinematics in race walking are restricted by the rules of the event and result in knee angular motions different from those in distance running, preventing race walkers from reaching the speeds attainable by distance runners
Recommended from our members
A Computational Model for Continuous Cooling of Injection Moulding Processes
This paper discusses the approaches and techniques used to build a realistic numerical model to analyse the cooling phase of the injection moulding process. The procedures employed to select an appropriate mesh and the boundary and initial conditions for the problem are discussed and justified. The final model is validated using direct comparisons with experimental results generated in an earlier study. The model is shown to be a useful tool for further studies aimed at optimising the cooling phase of the injection moulding process.
Using the numerical model provides additional information relating to changes in conditions throughout the process, which otherwise could not be deduced or assessed experimentally. These results, and other benefits related to the use of the model, are also discussed in the paper
Variation in pelvic morphology may prevent the identification of anterior pelvic tilt
Pelvic tilt is often quantified using the angle between the horizontal and a line connecting the anterior superior iliac spine (ASIS) and the posterior superior iliac spine (PSIS). Although this angle is determined by the balance of muscular and ligamentous forces acting between the pelvis and adjacent segments, it could also be influenced by variations in pelvic morphology. The primary objective of this anatomical study was to establish how such variation may affect the ASIS-PSIS measure of pelvic tilt. In addition, we also investigated how variability in pelvic landmarks may influence measures of innominate rotational asymmetry and measures of pelvic height. Thirty cadaver pelves were used for the study. Each specimen was positioned in a fixed anatomical reference position and the angle between the ASIS and PSIS measured bilaterally. In addition, side-to-side differences in the height of the innominate bone were recorded. The study found a range of values for the ASIS-PSIS of 0–23 degrees, with a mean of 13 and standard deviation of 5 degrees. Asymmetry of pelvic landmarks resulted in side-to-side differences of up to 11 degrees in ASISPSIS tilt and 16 millimeters in innominate height. These results suggest that variations in pelvic morphology may significantly influence measures of pelvic tilt and innominate rotational asymmetry
Braking characteristics during cutting and pivoting in female soccer players
Biomechanical studies into changing direction focus on final contact (FC), whilst limited research has examined penultimate contact (PEN). The aim of this study was to explore the kinematic and kinetic differences between PEN and FC of cutting and pivoting in 22 female soccer players (mean ± SD; age: 21 ± 3.1 years, height: 1.68 ± 0.07 m, mass: 58.9 ± 7.3 kg). Furthermore, the study investigated whether horizontal force-time characteristics during PEN were related to peak knee abduction moments during FC. Three dimensional motion analyses of cutting and pivoting on the right leg were performed using Qualysis ‘Pro-reflex’ infrared cameras (240Hz). Ground reaction forces (GRF) were collected from two AMTI force platforms (1200Hz) to examine PEN and FC. Both manoeuvres involved significantly (P < 0.05) greater knee joint flexion angles, peak horizontal GRF, but lower average horizontal GRF during PEN compared to FC. Average horizontal GRF during PEN (R = -0.569, R2 = 32%, P = 0.006) and average horizontal GRF ratio (R = 0.466, R2 = 22%, P = 0.029) were significantly related to peak knee abduction moments during the FC of cutting and pivoting, respectively. The results indicate PEN during pre-planned changing direction helps reduce loading on the turning leg where there is greater risk of injuries to knee ligaments
The influence of an off the shelf lateral wedge orthotic on knee loading during running
Knee injuries are prevalent in sports and associated with degenerative changes to the joint (Silverwood et al.,2015). High external knee adduction moments (EKAMs), knee adduction angular impulses (KAAIs) and knee flexion moments (KFMs) have been associated with increased cartilage deterioration (Chehab, Favre, Erhart-Hledik, & Andriacchi, 2014).
Lateral wedge insoles (LWIs) have demonstrated reductions in biomechanical loading (EKAM, KAAI) associated with osteoarthritis progression during walking in individuals with osteoarthritis (OA; Jones, Chapman, Forsythe, Parkes, & Felson, 2014). Younger individuals who sustain a knee injury during sport are likely to return to physical activity following treatment (Kim, Nagao, Kamata, Maeda, & Nozawa, 2013). With increased risk of developing knee OA, identifying preventative measures to delay the progression of OA during dynamic tasks such as running is required
The echinoderm innate humoral immune response
Abstract: Multicellular organisms have an immune system, which is essential for the survival of living beings. Interest in the immune system has been expanded since common characteristics of innate immunity between Drosophila melanogaster (Meigen, 1830) and mammals were discovered in the 1980. Since then, immunology has mainly focused on the adaptive immune system that seems to be restricted to vertebrates. Unlike the innate immunity, the adaptive one is acquired after exposure to a specific antigen (Ag) and includes: antigen-presenting cells such as macrophages, proliferation of B and T lymphocytes, Ag-specific antibody/cytokine production and immunological memory. Innate immunity is instead a process of cellular defense at low specificity, which is designed to prevent and combat infectious agents that penetrate at the tissue level, and may be the only form of immunity present in invertebrates such as sea urchins. The immune system of invertebrates acts through (i) cellular components (cell-mediated immunity) in which the effectors of defense reactions are represented by immune cells; (ii) soluble factors (humoral immunity), secreted by the immune cells, such as lectins, agglutinins, lysins, antimicrobial peptides and the prophenoloxidase (proPO) activating system, which act in parallel with the immune cells to fight pathogens and other foreign substances. Here we aim to deepen the study on humoral immunity of invertebrates, especially referring to the phylum Echinodermata because of its features shared with protostomes and other deuterostomes, and suggesting a key step during evolution
Dietary Intakes of Elite 14 - 19 Year Old English Academy Rugby Players During a Pre-Season Training Period.
Good nutrition is essential for the physical development of adolescent athletes, however data on dietary intakes of adolescent rugby players are lacking. This study quantified and evaluated dietary intake in 87 elite male English academy rugby league (RL) and rugby union (RU) players by age (under-16 (U16) and under-19 (U19) years old) and code (RL and RU). Relationships of intakes with body mass and composition (sum of 8 skinfolds) were also investigated. Using 4-day diet and physical activity diaries, dietary intake was compared to adolescent sports nutrition recommendations and the UK national food guide. Dietary intake did not differ by code, whereas U19s consumed greater energy (3366 ± 658 vs. 2995 ± 774 kcal.day-1), protein (207 ± 49 vs. 150 ± 53 g.day-1) and fluid (4221 ± 1323 vs. 3137 ± 1015 ml.day-1) than U16s. U19s consumed a better quality diet than U16s (greater intakes of fruit and vegetables; 4.4 ± 1.9 vs. 2.8 ± 1.5 servings.day-1; non-dairy proteins; 3.9 ± 1.1 vs. 2.9 ± 1.1 servings.day-1) and less fats and sugars (2.0 ± 1. vs. 93.6 ± 2.1 servings.day-1). Protein intake vs. body mass was moderate (r = 0.46, p < 0.001), and other relationships were weak. The findings of this study suggest adolescent rugby players consume adequate dietary intakes in relation to current guidelines for energy, macronutrient and fluid intake. Players should improve the quality of their diet by replacing intakes from the fats and sugars food group with healthier choices, while maintaining current energy, and macronutrient intakes
Optimisation of Continuous and Pulsed Cooling in Injection Moulding Processes
The concept of pulsed cooling in injection moulding involves cycling the flow of coolant in order that cooling only takes place as and when it is required, as opposed to continuous cooling, where the coolant in run through the channels throughout the entire process. It is claimed that using the pulsed cooling method, with reduced temperature coolants, may reduce cycle times and overall energy consumption for the injection moulding process, when compared with continuous cooling. It is also suggested that this is not at the expense of component integrity since common defects such as warpage, which could come about due to non-uniform cooling of the component, or impedance of flow of the polymer into the mould cavity during injection, do not normally appear.
The study described in this paper uses a previously validated numerical model in order to optimise the cooling phase of the injection moulding process, for both continuous and pulsed cooling, in order to assess the advantages and disadvantages of each method, with respect to cycle times. In addition, the optimisations were carried out with a view to improving cycle times experimentally, taking into consideration the findings of the study
A predicted astrometric microlensing event by a nearby white dwarf
We used the Tycho-Gaia Astrometric Solution catalogue, part of the Gaia Data
Release 1, to search for candidate astrometric microlensing events expected to
occur within the remaining lifetime of the Gaia satellite. Our search yielded
one promising candidate. We predict that the nearby DQ type white dwarf LAWD 37
(WD 1142-645) will lens a background star and will reach closest approach on
November 11th 2019 ( 4 days) with impact parameter mas. This
will produce an apparent maximum deviation of the source position of
mas. In the most propitious circumstance, Gaia will be able to
determine the mass of LAWD 37 to . This mass determination will
provide an independent check on atmospheric models of white dwarfs with helium
rich atmospheres, as well as tests of white dwarf mass radius relationships and
evolutionary theory
Drug misuse, tobacco smoking, alcohol and other social determinants of tuberculosis in UK-born adults in England: a community-based case-control study
Addressing social determinants of tuberculosis (TB) is essential to achieve elimination, including in
low-incidence settings. We measured the association between socio-economic status and intermediate
social determinants of health (SDHs, including drug misuse, tobacco smoking and alcohol), and TB,
taking into account their clustering in individuals. We conducted a case-control study in 23–38 years old
UK-born White adults with frst tuberculosis episode, and randomly selected age and sex frequencymatched community controls. Data was collected on education, household overcrowding, tobacco
smoking, alcohol and drugs use, and history of homelessness and prison. Analyses were done using
logistic regression models, informed by a formal theoretical causal framework (Directed Acyclic Graph).
681 TB cases and 1183 controls were recruited. Tuberculosis odds were four times higher in subjects
with education below GCSE O-levels, compared to higher education (OR=3.94; 95%CI: 2.74, 5.67),
after adjusting for other TB risk factors (age, sex, BCG-vaccination and stays ≥3 months in Africa/Asia).
When simultaneously accounting for respective SDHs, higher tuberculosis risk was independently
associated with tobacco smoking, drugs use (especially injectable drugs OR=5.67; 95%CI: 2.68, 11.98),
homelessness and area-level deprivation. Population Attributable Fraction estimates suggested that
tobacco and class-A drug use were, respectively, responsible for 18% and 15% of TB cases in this group.
Our fndings suggest that socio-economic deprivation remains a driver of tuberculosis in England,
including through drugs misuse, tobacco smoking, and homelessness. These fndings further support
the integration of health and social services in high-risk young adults to improve TB control eforts
- …