Errors in the estimation of hydration status from changes in body mass

Abstract

Hydration status is not easily measured, but acute changes in hydration status are often estimated from body mass change. Changes in body mass are also often used as a proxy measure for sweat losses. There are, however, several sources of error that may give rise to misleading results, and our aim in this paper is to quantify these potential errors. Respiratory water losses can be substantial during hard work in dry environments. Mass loss also results from substrate oxidation, but this generates water of oxidation which is added to the body water pool, thus dissociating changes in body mass and hydration status: fat oxidation actually results in a net gain in body mass as the mass of carbon dioxide generated is less than the mass of oxygen consumed. Water stored with muscle glycogen is presumed to be made available as endogenous carbohydrate stores are oxidized. Fluid ingestion and sweat loss complicate the picture by altering body water distribution. Loss of hypotonic sweat results in increased osmolality of body fluids. Urine and faecal losses can be measured easily, but changes in the water content of the bladder and the gastrointestinal tract cannot. Body mass change is not always a reliable measure of changes in hydration status and substantial loss of mass may occur without an effective net negative fluid balance.     

Test–retest reliability of a battery of field-based health-related fitness measures for adolescents

Abstract

The main aim of this study was to determine the test–retest reliability of existing tests of health-related fitness. Participants (mean age 14.8 years, s = 0.4) were 42 boys and 26 girls who completed the study assessments on two occasions separated by one week. The following tests were conducted: bioelectrical impedance analysis (BIA) to calculate percent body fat, leg dynamometer, 90° push-up, 7-stage sit-up, and wall squat tests. Intra-class correlation (ICC), paired samples t-tests, and typical error expressed as a coefficient of variation were calculated. The mean percent body fat intra-class correlation coefficient was similar for boys (ICC = 0.95) and girls (ICC = 0.93), but the mean coefficient of variation was considerably higher for boys than girls (22.2% vs. 12.2%). The boys' coefficients of variation for the tests of muscular fitness ranged from 9.0% for the leg dynamometer test to 26.5% for the timed wall squat test. The girls' coefficients of variation ranged from 17.1% for the sit-up test to 21.4% for the push-up test. Although the BIA machine produced reliable estimates of percent body fat, the tests of muscular fitness resulted in high systematic error, suggesting that these measures may require an extensive familiarization phase before the results can be considered reliable.     

Factor Structure and Measurement Invariance of a 10-Item Decisional Balance Scale: Longitudinal and Subgroup Examination Within an Adult Diabetic Sample

This study explores the longitudinal and subgroup measurement properties of a 10-item, physical activity decisional balance scale, previously published by Plotnikoff, Blanchard, Hotz, and Rhodes (2001 Plotnikoff, R. C., Blanchard, C., Hotz, S. B. and Rhodes, R. 2001. Validation of the decisional balance scales in the exercise domain from the Transtheoretical Model: A longitudinal test. Measurement in Physical Education and Exercise Science, 5: 191–206. [Taylor & Francis Online] , [Google Scholar]), within a diabetic sample of Canadian adults. Results indicated that a three-factor measurement model consistently improved model fit compared to the previously published two-factor model. Evidence of configural, metric, and scalar measurement invariance across time and among subgroups suggests that the 10-item decisional balance scale is appropriate for investigating associative relationships with other constructs and for comparing group means of the pros and cons subscales among a variety of diabetic population subgroups.     

A teacher education program in elementary science that connects content,methods, practicum,and student teaching

Conclusion To educate teachers who have adequate content knowledge, possess the necessary skills to implement effective teaching strategies, and are confident and have positive attitudes toward science and the teaching of science, alternative teaching models are necessary. The University of Wyoming model provides such an alternative. Based on observations and interviews of students and the mentor teachers, it is apparent that it has created a very positive response in prospective teachers who have participated in it. The Wyoming model provided an effective process to train future elementary teachers. Even though it focused on science, the basis is general enough that it could be successfully extended to other disciplines with only minor modifications; however, all of the major components of the Wyoming model are vital to its success. Content courses designed specifically for prospective teachers have been successful in giving the students the content knowledge and providing opportunities for effective modeling. The seminars provide strong mechanisms to connect content to methodology and make the content relevant to teaching and to children. Because of their modeling, peer coaching, and sharing their time and students, the mentor teachers are essential partners in helping the university educate future teachers. Finally, the cooperation of all partners—district administrators, teachers, science content and science education university faculty, and students—is necessary to provide early and continuous experiences to prospective teachers. This material is based upon work supported in part by a grant from the National Science Foundation (Grant No. TTE-8851105). Any opinions, findings, conclusions, and/or recommendations expressed in this article are those of the authors and do not necessarily reflect those of the NSF.     

Defining attitude for science educators

A distinct and complex definition of attitude is evolving within the literature. A mental readiness to respond and a correlational consistency between attitude and behavior—although controversial and in need of further study and analysis—remain viable subcomponents within the definition. Most agree that evaluation is the heartbeat of attitude. The impact of social influence on attitudes is becoming increasingly important. Attitudes are learned and not inherited.     

The Bleaching Syndrome: The Role of Educational Intervention

Per the Bleaching Syndrome, people of color, including African, Asian, and Latino Americans, are both victims and perpetrators of color discrimination. The Bleaching Syndrome encompasses perceptual, psychological, and behavioral sectors that affect students' schooling experiences. Education professionals, including teachers, administrators, and counselors, must address these factors to promote mental and emotional health among learners. In this article, I discuss how the Bleaching Syndrome and color bias affects dark-complexioned African American children in contemporary US schools.     

Writing method and productivity of science and engineering faculty

The present study aimed to describe the methods of writing used by university faculty and to explore relationships between method and productivity in writing. The survey reported here examined the cognitive strategies, tools, work scheduling, environment, and rituals used by 121 science and engineering faculty members in writing technical documents such as journal articles. The most commonly reported methods (e.g., the cognitive strategy of mentally planning large units of text structure and selecting a pen or pencil for a tool) were uncorrelated with reported productivity. Selecting a quiet work environment was the only typical habit that was associated with high productivity. Three other aspects of writing method were also related to high productivity, but they were not widely employed. These were using a dictation machine, preparing detailed written outlines before beginning a first draft, and the ritual of exercising vigorously before or during a writing session.     

Deaf and hearing students' morphological knowledge applied to printed English

The study examined the ability of deaf and hearing students at the college and middle school levels to discern and apply knowledge of printed word morphology. There were 70 deaf and 58 hearing participants. A two-part paper-and-pencil test of morphological knowledge examined subjects' ability to (a) perceive segmentation of morphemes within printed words and (b) recognize meanings associated with various printed morphemes. The hearing college students performed best on every dependent measure of the two-part test. The deaf college students scored significantly lower than the hearing college students but similarly to the hearing middle school students. Deaf middle school students consistently scored the lowest on both parts of the test. While all students' performance declined as the difficulty of the morphemic content increased within both tasks, the decline was greatest among middle school deaf students. Although segmentation and semantic analysis skills necessary to morphographic decoding were apparent in the deaf students, their mastery levels fell significantly below those of the hearing subjects.