Competitive swimmers with hypermobility have strength and fatigue deficits in shoulder medial rotation

Generalised Joint Hypermobility including shoulder hypermobility (GJHS) in swimmers is considered an intrinsic risk factor for shoulder injuries. The aim was to investigate the association of GJHS with shoulder strength, fatigue development and muscle activity during swimming-related shoulder rotations. Totally, 38 competitive swimmers (aged 13–17 years) participated, 19 were competitive swimmers with GJHS and 19 were age, sex and club matched swimmers without GJHS. Concentric isokinetic force in medial and lateral rotations were measured at 60°/s (5 repetitions) and 180°/s (10 repetitions). Electromyographic activity was measured from upper trapezius, lower trapezius, serratus anterior, infraspinatus and pectoralis major muscles. Swimmers with GJHS produced significantly lower peak torque (0.53 vs. 0.60 Nm/kg; p =.047) and maximum work (0.62 vs. 0.71 J/kg; p =.031) than controls during medial rotation (60°/s). Swimmers with GJHS showed significantly larger isokinetic fatigue at 180°/s (0.321 J/repetition; p =.010), and tendencies to lower levels of muscle activity in infraspinatus (20%, p =.066) and pectoralis major (34%, p =.092) at 60°/s during medial rotation. Young competitive swimmers with GJHS, despite no formal diagnosis, displayed strength and fatigue deficits in medial rotation, potentially inherent with greater risk of shoulder injury. Whether GJHS swimmers benefit from medial rotation strengthening is an important topic for future studies.</p

Parametrized K-theory

In nature, one observes that a K-theory of an object is defined in two steps. First a “structured” category is associated to the object. Second, a K-theory machine is applied to the latter category that produces an infinite loop space. We develop a general framework that deals with the first step of this process. The K-theory of an object is defined via a category of “locally trivial” objects with respect to a pretopology. We study conditions ensuring an exact structure on such categories. We also consider morphisms in K-theory that such contexts naturally provide. We end by defining various K-theories of schemes and morphisms between them

Competitive swimmers with hypermobility have strength and fatigue deficits in shoulder medial rotation

Generalised Joint Hypermobility including shoulder hypermobility (GJHS) in swimmers is considered an intrinsic risk factor for shoulder injuries. The aim was to investigate the association of GJHS with shoulder strength, fatigue development and muscle activity during swimming-related shoulder rotations. Totally, 38 competitive swimmers (aged 13–17 years) participated, 19 were competitive swimmers with GJHS and 19 were age, sex and club matched swimmers without GJHS. Concentric isokinetic force in medial and lateral rotations were measured at 60°/s (5 repetitions) and 180°/s (10 repetitions). Electromyographic activity was measured from upper trapezius, lower trapezius, serratus anterior, infraspinatus and pectoralis major muscles. Swimmers with GJHS produced significantly lower peak torque (0.53 vs. 0.60 Nm/kg; p =.047) and maximum work (0.62 vs. 0.71 J/kg; p =.031) than controls during medial rotation (60°/s). Swimmers with GJHS showed significantly larger isokinetic fatigue at 180°/s (0.321 J/repetition; p =.010), and tendencies to lower levels of muscle activity in infraspinatus (20%, p =.066) and pectoralis major (34%, p =.092) at 60°/s during medial rotation. Young competitive swimmers with GJHS, despite no formal diagnosis, displayed strength and fatigue deficits in medial rotation, potentially inherent with greater risk of shoulder injury. Whether GJHS swimmers benefit from medial rotation strengthening is an important topic for future studies.</p

Orientation-Dependent Oxygen Evolution on RuO₂ without Lattice Exchange

RuO₂ catalysts exhibit record activities toward the oxygen evolution reaction (OER), which is crucial to enable efficient and sustainable energy storage. Here we examine the RuO₂ OER kinetics on rutile (110), (100), (101), and (111) orientations, finding (100) the most active. We assess the potential involvement of lattice oxygen in the OER mechanism with online electrochemical mass spectrometry, which showed no evidence of oxygen exchange on these oriented facets in acidic or basic electrolytes. Similar results were obtained for polyoriented RuO₂ films and particles, in contrast to previous work, suggesting lattice oxygen is not exchanged in catalyzing OER on crystalline RuO₂ surfaces. This hypothesis is supported by the correlation of activity with the number of active Ru-sites calculated by density functional theory, where more active facets bind oxygen more weakly. This new understanding of the active sites provides a design strategy to enhance the OER activity of RuO₂ nanoparticles by facet engineering

A Facile Synthesis of Size-Controllable IrO2 and RuO2 Nanoparticles for the Oxygen Evolution Reaction

The efficiency of the water electrolysis process is restricted by the sluggish kinetics of the oxygen evolution reaction (OER). Developing efficient catalysts and their synthesis methods is highly desired to improve the kinetics of the OER and therefore the overall efficiency of the water electrolysis. In this report, we present a facile wet-chemical method for synthesizing IrO2 and RuO2 nanoparticles (NPs) for the OER. The nanoparticles were synthesized by reducing metal chlorides in ethylene glycol in the presence of polyvinylpyrrolidone, followed by annealing in air. The particle size was controlled by adjusting the annealing temperature. The activity of IrO2 and RuO2 NPs supported on carbon black was investigated by cyclic voltammetry (CV) in alkaline (0.1 M KOH) electrolyte. As-synthesized IrO2 and RuO2 NPs showed high OER activity. The IrO2 NPs exhibited a specific activity of up to 3.5 (±1.6) μA/cm2oxide at 1.53 V (vs. RHE), while the RuO2 NPs achieved a value of 124.2 (±8) μA/cm2oxide. Moreover, RuO2 NPs showed a mass activity for OER, up to 102.6 (±10.5) A/goxide at 1.53 V (vs. RHE), which represents the highest value reported in the literature to date.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore