Circulatory effects of fluid loss and fluid intake during exercise

Abstract

Cardiorespiratory responses to two levels of exercise (133 and 200 W) on a bicycle ergometer were measured in nine subjects before and after a 1‐h outdoor run of 12.8 km completed in ambient temperatures of 20–25° C. After the run, the subjects showed a mean weight loss of 1.49 kg; the laboratory exercises produced higher mean levels of O2 consumption than before the run (1.91 and 2.66 1 min‐1 compared with 1.80 and 2.46 1 min‐1) and higher mean heart rates (141 and 158 beats min‐1 compared with 115 and 140 beats min‐1); and lower levels of stroke volume (83 and 85 ml compared with 109 and 101 ml) and of cardiac output (11.6 and 13.3 1 min‐1 compared with 12.6 and 14.1 1 min‐1). Five subjects were studied in a similar way on a second occasion when they consumed 1.25 1 of a dextrose‐electrolyte solution during the first 45 min of the outdoor run. Differences in the exercise variables measured before and after the outdoor run were now small or insignificant. It is postulated that in the first study uncompensated loss of body water reduced plasma volume and cardiac filling, thus reducing stroke volume and cardiac output. Such changes jeopardize body temperature regulation during exercise.     

Drawing space: mathematicians’ kinetic conceptions of eigenvectors

This paper explores how mathematicians build meaning through communicative activity involving talk, gesture and diagram. In the course of describing mathematical concepts, mathematicians use these semiotic resources in ways that blur the distinction between the mathematical and physical world. We shall argue that mathematical meaning of eigenvectors depends strongly on both time and motion—hence, on physical interpretations of mathematical abstractions—which are dimensions of thinking that are typically deliberately absent from formal, written definition of the concept. We shall also show how gesture and talk contribute differently and uniquely to mathematical conceptualisation and further elaborate the claim that diagrams provide an essential mediating role between the two.     

The incorporation of health and welfare risks into technological forecasting

The application of the outputs of scientific and technological development to industry snd society brings with it a shift in the pattern and distribution of health and safety risks to worker, user and third party. A quatitative method is suggested of measuring and controlling this reduction in an economic and socially acceptable way os that both growth and quality of life may be preserved.     

Teacher-student discourse in active learning lectures: case studies from undergraduate physics

In this paper we develop knowledge of the discourse that takes place between teacher and students in two large undergraduate classes which use a flipped, active learning approach. In flipped classes students encounter the content through pre-class resources, freeing up class time for more active engagement with the material. This results in increased opportunities for teacher-student interactions which may be beneficial for learning. Our aim here is to explore the nature and purposes of these dialogues. Two case studies from introductory physics classes at the University of Edinburgh are analysed through a sociocultural perspective. Three main purposes of dialogues are observed: (1) Involving students in sense-making, (2) Guided expert modelling and (3) Wonderment questions. We found that the dialogues predominantly use a triadic Initiation, Response, Feedback (IRF) format and are authoritative in nature, but work together to create an interactive learning environment that can be described as ‘ideologically dialogic’     

Preservice teachers’ perceptions of learning environments before and after pandemic-related course disruption

Learning Environments Research - When the 2020 semester began in the USA in January, it was unimaginable that the near-total closure of educational system across the globe would become the new...