Does field hockey increase morphofunctional asymmetry? A pilot study.

Common practice in field hockey requires athletes to adopt a semi-crouched posture, so players have a greater risk of musculoskeletal disorders than non-athletes. The aim of the present study was to assess how field hockey determines asymmetry in morphological and functional characteristics of the body by comparing athletes to control participants. The sample consisted of 15 male field hockey players from the Polish Youth National Team and 14 male university students. Antimeric differences in the chosen variables between body sub-regions were assessed. All morphological characteristics (bone mineral density, fat mass, and lean mass) were estimated using a dual energy X-ray absorptiometry. Additionally, the range of motion in transverse and frontal planes of the cervical, thoracic and lumbar spine was measured by using an electrogoniometric system. The results showed that the values of all morphological characteristics were higher in the left body segments, both in athletes and controls. However, the differences between sides were much more pronounced in the field hockey players. With regard to functional traits, higher values were obtained for the right body side in athletes but for the left side of the body among the controls. The difference between right and left side bending increased from the cervical spine (2.7%) through thoracic spine (7.8%) to lumbar spine (16.5%) in athletes. Rotational asymmetry in the thoracic spine was the largest in both groups. These findings indicate that it is important to monitor all athletes to prevent injury and health problems connected with strong morphological asymmetry.

Effects of supplementation with acai (Euterpe oleracea Mart.) berry-based juice blend on the blood antioxidant defence capacity and lipid profile in junior hurdlers. A pilot study.

The purpose of this pilot study was to examine whether regular consumption of an acai berry-based juice blend would affect sprint performance and improve blood antioxidant status and lipid profile in junior athletes. Seven junior hurdlers (17.5±1.2 years) taking part in a pre-season conditioning camp were supplemented once a day, for six weeks, with 100 ml of the juice blend. At the start and the end of the camp the athletes performed a 300-m sprint running test on an outdoor track. Blood samples were taken before and immediately after the test and after 1 h of recovery. Blood antioxidant status was evaluated based on activities of antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GSH-Px], glutathione reductase [GR]), concentrations of non-enzymatic antioxidants (reduced glutathione [GSH], uric acid), total plasma polyphenols, ferric reducing ability of plasma (FRAP), thiobarbituric acid reactive substances (TBARS) and activities of creatine kinase (CK) and lactate dehydrogenase (LDH) as muscle damage markers. In order to evaluate potential health benefits of the acai berry, the post-treatment changes in lipid profile parameters (triglycerides, cholesterol and its fractions) were analysed. Six weeks' consumption of acai berry-based juice blend had no effect on sprint performance, but it led to a marked increase in the total antioxidant capacity of plasma, attenuation of the exercise-induced muscle damage, and a substantial improvement of serum lipid profile. These findings strongly support the view of the health benefits of supplementation with the acai berry-based juice blend, mainly attributed to its high total polyphenol content and the related high in vivo antioxidant and hypocholesterolaemic activities of this supplement.

The plasma protein fibrinogen stabilizes clusters of red blood cells in microcapillary flows.

The supply of oxygen and nutrients and the disposal of metabolic waste in the organs depend strongly on how blood, especially red blood cells, flow through the microvascular network. Macromolecular plasma proteins such as fibrinogen cause red blood cells to form large aggregates, called rouleaux, which are usually assumed to be disaggregated in the circulation due to the shear forces present in bulk flow. This leads to the assumption that rouleaux formation is only relevant in the venule network and in arterioles at low shear rates or stasis. Thanks to an excellent agreement between combined experimental and numerical approaches, we show that despite the large shear rates present in microcapillaries, the presence of either fibrinogen or the synthetic polymer dextran leads to an enhanced formation of robust clusters of red blood cells, even at haematocrits as low as 1%. Robust aggregates are shown to exist in microcapillaries even for fibrinogen concentrations within the healthy physiological range. These persistent aggregates should strongly affect cell distribution and blood perfusion in the microvasculature, with putative implications for blood disorders even within apparently asymptomatic subjects.

On coupling between the orientation and the shape of a vesicle under a shear flow.

A simple 2D model of deformable vesicles tumbling in a shear under flow is introduced in order to account for the main qualitative features observed experimentally as shear rates are increased. The simplicity of the model allows for a full analytical tractability while retaining the essential physical ingredients. The model reveals that the main axes of the vesicle undergo oscillations which are coupled to the vesicle orientation in the flow. The model reproduces and sheds light on the main novel features reported in recent experiments [M. Mader et al., Eur. Phys. J. E. 19, 389 (2006)], namely that both coefficients A and B that enter the Keller-Skalak equation, d psi/dt = A+B cos(2 psi) (psi is the vesicle orientation angle in the shear flow), undergo a collapse upon increasing shear rate.

Dynamics of viscous vesicles in shear flow.

The dynamics of giant lipid vesicles under shear flow is experimentally investigated. Consistent with previous theoretical and numerical studies, two flow regimes are identified depending on the viscosity ratio between the interior and the exterior of the vesicle, and its reduced volume or excess surface. At low viscosity ratios, a tank-treading motion of the membrane takes place, the vesicle assuming a constant orientation with respect to the flow direction. At higher viscosity ratios, a tumbling motion is observed in which the whole vesicle rotates with a periodically modulated velocity. When the shear rate increases, this tumbling motion becomes increasingly sensitive to vesicle deformation due to the elongational component of the flow and significant deviations from simpler models are observed. A good characterization of these various flow regimes is essential for the validation of analytical and numerical models, and to relate microscopic dynamics to macroscopic rheology of suspensions of deformable particles, such as blood.

Corners, cusps, and pearls in running drops.

Small drops sliding down a partially wetting substrate bifurcate between different shapes depending on their capillary number Ca. At low Ca, they are delimited by a rounded, smooth contact line. At intermediate values they develop a corner at the trailing edge, the angle of which evolves from flat to 60 degrees with increasing velocity. Further up, they exhibit a cusped tail that emits smaller drops ("pearls"). These bifurcations may be qualitatively and quantitatively recovered by considering the dynamic contact angle along the contact line.