Interpretation of crank torque during an all-out cycling exercise at high pedal rate

The use of cycle ergometers with strain gauges bonded on to the cranks enables the evaluation of strength, velocity and power. However, the torque measured at the end of downstroke is higher at high velocity than at medium velocity in contradiction with the force–velocity relationship. Kinematic data were collected with a camera during sprints on a Lode ergometer with strain gauges. Leg mechanical energy (E _Leg) and its derivative (dE _Leg/dt) were calculated from the sum of the kinetic and potential energies. The opposition of P _ext (output at crank level) and dE _Leg/dt before bottom dead centre suggested a transformation of E _Leg into external work, explaining the higher torque at the end of downstroke at peak velocity. Another explanation is that the leg muscles worked on different parts of their torque–angle relationships as the phase between knee and ankle angles was different at low and high cycling frequencies. Musculo-skeletal net power output (algebraic sum of P _ext and dE _Leg/dt) indicated that musculo-skeletal structures participated in the upward movement, whereas P _ext was negative.     

To tag or not to tag? How to support organizing and classifying bookmarks from the Web (¿Con etiquetas o sin etiquetas? Cómo asistir en la organización y clasificación de los marcadores de páginas Web) (¿Con etiquetas o sin etiquetas? Cómo asistir en la organización y clasificación de los marcadores de páginas Web)

ABSTRACT

When searching for information on the Internet, it can be stored in a bookmarking system. The ability to organize this information in such a system depends on one’s own prior knowledge to create an appropriate classification scheme. Providing a classification system for bookmarks might support people with low prior knowledge. Even though different bookmarking systems exist, hierarchical menus and tagging are being most widely used. In the current exploratory study with 95 ninth-grade students, a 2 × 2 between-subjects design was used to investigate the influence of providing classification support (or not) for either a tagging or a hierarchical system. Results showed that despite the low familiarity with tagging systems, using a hierarchical system is not necessarily a better approach than using a tagging system to organize previously found information. Rather, a tagging system seems to yield storage of fewer but higher-quality information sources. The most important conclusion is that, despite the low familiarity with tagging systems, using a hierarchical system was not beneficial over using a tagging system to organize previously found information.     

Maximum temperature in fixed-bed sorption columns and isosteric heats of adsorption

Heat effects in fixed-bed sorption columns are often quite large and have a pronounced effect on the sorption kinetics. Proper design of such systems must include consideration of these effects.A method is developed for computing the maximum possible bed temperature. The model is tested on two systems: (1) the Linde molecular sieve 4 A/water system and (2) the Alcoa activated alumina F-1/water system. Since the predicted temperatures appeared to be low for the latter system, the model was refined by the inclusion of the isosteric integral heat of adsorption. Tests on the activated alumina show considerable improvement.The isosteres of two sorption therm correlations are investigated. The results show that the heat of adsorption of water on the alumina varies logarithmically with sorbate concentration—approaching high values at low concentrations and approaching the heat of vaporization of water at high concentrations. The results also suggest that the isosteric heat of adsorption behavior may be of use in assessing the “goodness of fit” of sorption therm correlations.     

Home advantage in speed skating: Evidence from individual data

Home advantage is a well-documented phenomenon in many sports. Home advantage has been shown to exist for team sports (soccer, hockey, football, baseball, basketball) and for countries organizing sports tournaments like the Olympics and World Cup Soccer. There is also some evidence for home advantage in some individual sports, but there is a much more limited literature. This paper addresses the issue of home advantage in speed skating. From a methodological point of view, it is difficult to identify home advantage, because skaters vary in their abilities and the conditions of tournaments vary. There is a small but significant home advantage using a generalized linear mixed model, with random effects for skaters and fixed effects for skating rinks and seasons. Even though the home advantage effect exists, it is very small when compared to variation in skating times due to differences of rinks and individual abilities.     

Standardization of search methods for guideline development: an international survey of evidence-based guideline development groups

BACKGROUND: Effective literature searching is particularly important for clinical practice guideline development. Sophisticated searching and filtering mechanisms are needed to help ensure that all relevant research is reviewed. PURPOSE: To assess the methods used for the selection of evidence for guideline development by evidence-based guideline development organizations. METHODS: A semistructured questionnaire assessing the databases, search filters and evaluation methods used for literature retrieval was distributed to eight major organizations involved in evidence-based guideline development. RESULTS: All of the organizations used search filters as part of guideline development. The medline database was the primary source accessed for literature retrieval. The OVID or SilverPlatter interfaces were used in preference to the freely accessed PubMed interface. The Cochrane Library, embase, cinahl and psycinfo databases were also frequently used by the organizations. All organizations reported the intention to improve and validate their filters for finding literature specifically relevant for guidelines. DISCUSSION: In the first international survey of its kind, eight major guideline development organizations indicated a strong interest in identifying, improving and standardizing search filters to improve guideline development. It is to be hoped that this will result in the standardization of, and open access to, search filters, an improvement in literature searching outcomes and greater collaboration among guideline development organizations.     

Effects of periodic carbohydrate ingestion on endurance and cognitive performances during a 40-km cycling time-trial under normobaric hypoxia in well-trained triathletes

The purpose of this study was to examine CHO ingestion on a cognitive task using a field-simulated time-trial (TT) under hypoxia in well-trained triathletes. Ten male triathletes (age: 22.1 ± 1.1 years; VO₂max: 59.4 ± 1.4 ml/kg/min) participated in this double-blind/crossover/counter-balanced design study. Participants completed 3 TT trials: 1) normoxic placebo (NPLA; FiO₂ = 20.9%), 2) hypoxic placebo (HPLA; FiO₂ = 16.3%), and 3) hypoxic CHO (HCHO; 6% CHO provided as 2 ml/kg/15 min; FiO₂ = 16.3%). During the TT, physiological responses (SpO₂, HR, RPE, and blood glucose/lactate), cognitive performance, and cerebral haemodynamics were measured. Hypoxia reduced TT performance by ~3.5–4% (p < 0.05), but CHO did not affect TT performance under hypoxia. For the cognitive task, CHO slightly preserved exercise-induced cognitive reaction speed but did not affect response accuracy during hypoxic exercise. However, CHO did not preserve the decreased Hb-Diff (cerebral blood flow, CBF) and increased HHb in the prefrontal lobe (p < 0.05) during hypoxic exercise, and CHO failed to preserve hypoxia-suppressed prefrontal CBF and tissue oxygen saturation. In conclusion, the present study demonstrates that CHO is effective in sustaining reaction speed for a cognitive task but not promoting TT performance during hypoxic exercise, which would be important for strategy-/decision-making when athletes compete at moderate high-altitude.