Physical Load Affects Perceptual-Cognitive Performance of Skilled Athletes: a Systematic Review

BACKGROUND: Many researchers have considered the impact of physical exercise on perceptual-cognitive performance. There have also been a substantial number of studies that have examined how perceptual-cognitive skills differ between elite athletes and non-athletes. However, the knowledge on how physical exercise interacts with perceptual-cognitive skill is limited. This systematic review aims to provide detailed information on how athletes’ perceptual-cognitive performance is influenced by acute physical exercise load and whether these effects differ between elite athletes and lesser skilled groups. METHODS: A systematic review was conducted using different combinations of the keywords physical load, acute, exercise, perception, cognition, perceptual, cognitive, sport, and athlete with the PubMed and SportDiscus databases. Additional articles were found through screening the references of these papers. Articles had to (a) be full journal articles written in English, (b) include an athlete sample, (c) examine acute effects of physical exercise, and (d) measure a perceptual-cognitive task as the dependent variable. RESULTS: Twenty-six articles matched the inclusion criteria. Results suggested the impact of acute physical exercise on perceptual-cognitive performances of athletes depends on the specificity of the induced exercise and perceptual-cognitive task. Additionally, speed and accuracy were influenced differently by physical exercise. Furthermore, skilled athletes seem to be more positively influenced by acute physical exercise than novices. CONCLUSION: Since many factors influence perceptual-cognitive expertise, future research should be highly precise (e.g., regarding the definition of variables, the intensity of the physical exercise) and specific (e.g., regarding the tasks used, the type of the physical exercise)

The influence of laccase on the chemo-enzymatic synthesis of lignin graft-copolymers

The mechanism unterlying the chemo-enzymatic graft copolymerization of lignin with acrylic compounds was studied. When lignin sulfonate (LS) was incubated with the phenoloxidase laccase in the presence of a peroxide species (t-butylhydroperoxide, i.e. t-BHP), the decrease of the phenolic groups was significantly higher than when LS was incubated with laccase or t-BHP, separately. The enzymatic oxidation of the phenolic groups did lead to the formation of quinones however, the number of quinone groups formed in LS in the presence of t-BHP? was not significantly higher than in its absence. Still, a certain proportion of the quinones formed in the presence of t-BHP appeared to be further oxidized resulting in an opening of the aromatic rings. In addition, the rate of LS polymerization, i.e. its increase in (M) over bar (w) instigated by laccase, was significantly reduced in the presence of t-BHP even though the activity of laccase was only slightly affected by the peroxide. Incubation of LS with laccase prior to the grafting reaction resulted in a significant increase of die spin concentration as detected in the EPR spectra. In spite of a high steady state concentration of radicals, the generation rate of these radicals in pre-incubated LS was lower than in unpretreated LS. Thus, the polymer yields obtained with pre-incubated LS were lower than those obtained with unpretreated LS. (C) 2002 Elsevier Science Inc. All rights reserved