Despite the prevalence of caffeine as an ergogenic aid, few studies have examined the use of caffeinated gums, especially during half-time in team sports. The physiological (blood lactate, salivary hormone concentrations) and performance (repeated sprints, cognitive function) effects of consuming caffeine gum during a simulated half-time were examined. Professional academy rugby union players (n=14) completed this double-blind, randomized, counterbalanced study. Following pre-exercise measurements , players chewed a placebo (PL) gum for five min before a standardized warm-up and completing repeated sprint testing (RSSA1). Thereafter, during a 15 min simulated half-time period, players chewed either caffeine (CAF: 400 mg; 4.1 ± 0.5 mg·kg) or PL gum for five min before completing a second repeated sprint test (RSSA2). Blood lactate, salivary testosterone and cortisol concentrations, and indices of cognitive function (i.e., reaction time and Stroop test) were measured at baseline, pre-RSSA1, post-RSSA1, pre-RSSA2 and post-RSSA2. Sprint performance was not affected by CAF (P=0.995) despite slower sprint times following the first sprint of both RSSA tests (all P<0.002). Following half-time, salivary testosterone increased by 70% (+97±58 pg·mL) in CAF versus PLA (P<0.001) whereas salivary cortisol remained unchanged (P=0.307). Cognitive performance was unaffected by time and trial (all P>0.05). Although performance effects were absent, chewing caffeine gum increased the salivary testosterone concentrations of professional rugby union players over a simulated half-time. Practitioners may therefore choose to recommend caffeine gum between successive exercise bouts due to the increases in salivary testosterone observed; a variable associated with increased motivation and high-intensity exercise performance.
Aggregate scores from this modified screening tool rank heart failure patients according to their "risk of poor self-care" demonstrating that the Heart-FaST items constitute a meaningful scale to identify heart failure patients at risk of poor engagement in heart failure self-care.
Uncertainty quantification (UQ) and propagation are critical to the computational assessment of structural components and systems. In this work, we discuss the practical challenges of implementing uncertainty quantification for high-dimensional computational structural investigations, specifically identifying four major challenges: (1) Computational cost; (2) Integration of engineering expertise; (3) Quantification of epistemic and model-form uncertainties; and (4) Need for V&V, standards, and automation. To address these challenges, we propose an approach that is straightforward for analysts to implement, mathematically rigorous, exploits analysts' subject matter expertise, and is readily automated. The proposed approach utilizes the Latinized partially stratified sampling (LPSS) method to conduct small sample Monte Carlo simulations. A simplified model is employed and analyst expertise is leveraged to cheaply investigate the best LPSS design for the structural model. Convergence results from the simplified model are then used to design an efficient LPSS-based uncertainty study for the high-fidelity computational model investigation. The methodology is carried out to investigate the buckling strength of a typical marine stiffened plate structure with material variability and geometric imperfections.
Loosely coupled schemes for structural-acoustic coupling are examined that obtain the same order of accuracy as the monolithic scheme. The coupling algorithms are implemented in Sierra-SD, a massively parallel finite element application for structural dynamics and acoustics. By adapting the predictor-corrector scheme of Farhat et al. (2006), second order time accuracy is achieved with the loosely coupled approach. Node-to-face mappings allow arbitrary discretizations of the structural-acoustic interface. Convergence rates are verified with a one dimensional piston problem with known solution. Numerical results are compared to a shock induced plate experimental benchmark. Computational times for loose and strong coupling are compared for a sphere scattering problem. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.
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