儿童青少年运动员的营养需要

1. 儿童青少年运动员应该食用多样化的食物，其中，蛋白质应占膳食总能量的12％-15％，碳水化合物至少占55％，而脂肪至多占30％。日常生活中如何吃才能满足这些要求呢？膳食指南宝塔提供了一条可行之道。2.有些营养素对热爱运动的儿童青少年运动员非常重要，要保证摄入充足，这些营养素是碳水化合物（包括纤维素）、维生素B6、维生素D、铁、钙、镁、锌、铬。科学合理、包罗各类食物的平衡膳食，对青少年运动员最大程度地全面摄取各种营养素，满足生长发育和运动训练的需要，是非常必要的。3.鼓励儿童青少年运动员在运动训练前、中、后进行补液，以避免脱水的发生。4.如果膳食合理平衡，就没必要额外补充营养品。     

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.     

Population differences in constructive memory

An experiment was conducted to evaluate constructive memory in fourth-grade low-SES black and middle-SES white children. The children were read nine short passages; each passage was composed of two premise statements and a filler sentence. The children were tested by a recognition procedure. Thirty-six test sentences were presented randomly. Four sentences were associated with each passage (true premise, false premise, true inference, and false inference). Subjects were asked to make yes/no recognition decisions based on whether the test sentence was identical to a sentence presented at study. Middle-SES white children made few errors, except to true inference test sentences. This pattern of performance is consistent with the constructive view of memory. Low-SES black children also had a high error rate to true inference items. However, this outcome may not reflect constructive memory because they also had a high error rate to some of the other types of test sentences.     

Collaboration between 3- and 4-year-olds in self-initiated play on instruments

This article reports on a study of collaborative music-making on instruments among 3- and 4-year-old children. An area equipped with musical instruments was provided as a free-choice play option in an early childhood setting and a fixed camera recorded the children's play continuously during a number of visits. From the total 17 h of data five episodes of paired play were selected. Through a process of comparison across these episodes, it was established that children were coordinating their play through a repertoire of communicative and expressive behaviours. One episode of paired play considered to be representative was micro-analysed in detail.