Changes in energy availability across the season in Division I female soccer players

Abstract

Low energy availability [(energy intake – exercise expenditure)/kg lean body mass], a component of the Female Athlete Triad, has been associated with menstrual disturbances and low bone mass. No studies have examined the energy availability of athletes across a season. The purpose of this study was to assess the prevalence of, and what contributes to, low energy availability in Division I female soccer players across a season. Nineteen participants aged 18–21 years (mean [Vdot]O_2max: 57.0 ± 1.0 mL · kg^?1 · min^?1) were studied during the pre, mid, and post season. Mean energy availability was overall lowest at mid season, and lower at mid than post season (35.2 ± 3.7 vs. 44.5 ± 3.7 kcal · kg^?1 lean body mass, P = 0.009). Low energy availability (<30 kcal · kg^?1 lean body mass) was observed in 5/19 (26.3%), 5/15 (33.3%), and 2/17 (11.8%) of participants during the pre, mid, and post season. Dietary energy intake was lower mid (P = 0.008) and post season (P = 0.022) than it was pre season (pre: 2794 ± 233 kcal · day^?1; mid: 2208 ± 156 kcal · day^?1; post: 2161 ± 143 kcal · day^?1). Exercise energy expenditure decreased significantly (P ≤ 0.001) over time (pre: 819 ± 57 kcal · day^?1; mid: 642 ± 26 kcal · day^?1; post: 159 ± 28 kcal · day^?1). Low energy availability was due to lower dietary energy intake at lunch during pre season (P = 0.014) and during lunch and dinner during mid season (P ≤ 0.030). Energy availability was inversely related to body dissatisfaction (r = ?0.62, P = 0.017) and drive for thinness (r = ?0.55, P = 0.041) during mid season. Although most Division I female soccer players are not at risk for low energy availability, a concerning proportion exhibited low energy availability at pre or mid season. Further studies are needed to explore strategies to prevent and monitor low energy availability in these athletes.     

Energy turnover during 24 hours and 6 days of adventure racing

Abstract

Energy turnover was assessed in two conditions of mixed ultra-endurance exercise. In Study 1, energy expenditure and intake were measured in nine males in a laboratory over 24 h. In Study 2, energy expenditure was assessed in six males during an 800-km Adventure race (mean race time 152.5 h). Individual correlations between heart rate and oxygen uptake ([Vdot]O₂) were established during pre-tests when kayaking, cycling, and running. During exercise, energy expenditure was estimated from continuous heart rate recordings. Heart rate and [Vdot]O₂ were measured regularly during fixed cycling work rates to correct energy expenditure for drift in oxygen pulse. Mean energy expenditure was 18,050 ± 2,390 kcal (750 ± 100 kcal · h^?1) and 80,000 ± 18,000 kcal (500 ± 100 kcal · h^?1) in Study 1 and Study 2 respectively, which is higher than previously reported. Energy intake in Study 1 was 8,450 ± 1,160 kcal, resulting in an energy deficit of 9,590 ± 770 kcal. Body mass decreased in Study 1 (?2.3 ± 0.8 kg) but was unchanged in Study 2. Fat mass decreased in Study 2 (?2.3 ± 1.5 kg). In Study 1, muscle glycogen content decreased by only 60%. Adventure racing requires a high energy expenditure, with large inter-individual variation. A large energy deficit is caused by inadequate energy intake, possibly due to suppressed appetite and gastrointestinal problems. The oxygen pulse, comparing start to 12 h of exercise and beyond, increased by 10% and 5% in Study 1 and Study 2 respectively. Hence, estimations of energy expenditure from heart rate recordings should be corrected according to this drift.     

Parallel assessment of nutrition and activity in athletes: Validation against doubly labelled water, 24-h urea excretion,and indirect calorimetry

Abstract

The assessment of nutrition and activity in athletes requires accurate and precise methods. The aim of this study was to validate a protocol for parallel assessment of diet and exercise against doubly labelled water, 24-h urea excretion, and respiratory gas exchange. The participants were 14 male triathletes under normal training conditions. Energy intake and doubly labelled water were weakly associated with each other (r = 0.69, standard error of estimate [SEE] = 304 kcal · day^?1). Protein intake was strongly correlated with 24-h urea (r = 0.89) but showed considerable individual variation (SEE = 0.34 g · kg^?1 · day^?1). Total energy expenditure based on recorded activities was highly correlated with doubly labelled water (r = 0.95, SEE = 195 kcal · day^?1) but was proportionally biased. During running and cycling, estimated exercise energy expenditure was highly correlated with gas exchange (running: r = 0.89, SEE = 1.6 kcal · min^?1; cycling: r = 0.95, SEE = 1.4 kcal · min^?1). High exercise energy expenditure was slightly underestimated during running. For nutrition data, variations appear too large for precise measurements in individual athletes, which is a common problem of dietary assessment methods. Despite the high correlations of total energy expenditure and exercise energy expenditure with reference methods, a correction for systematic errors is necessary for the valid estimation of energetic requirements in individual athletes.     

Energy substrate metabolism during dual work rate exercise: Effects of order

Changes in workload are evident during many physical activities. The aim of this study was to assess total substrate metabolism when the temporal placement of a period of higher-intensity work (75% VO 2max ) was varied within a low-intensity exercise session (50% VO 2max ). One experimental trial (higher intensity first) comprised 5 min low-intensity work, followed by 15 min high-intensity work, followed by 40 min low-intensity work. The other trial (low intensity first) comprised 40 min low-intensity work, followed by 15 min high-intensity work, followed by 5 min low-intensity work. The trials were designed to achieve an identical total energy expenditure. Energy expenditure, fat and carbohydrate utilization were estimated by expired gas analysis and compared between conditions. Mean total energy expenditure during the higher-intensity phase was 1076 kJ and 1128 kJ in the high-intensity first and low-intensity first trials respectively (t 6 = -3.76, P = 0.0047). Mean total energy expenditure for the whole trial was 3356 kJ and 3452 kJ in the high-intensity first and low-intensity first trials respectively (t 6 = -3.48, P = 0.0065). Mean whole-trial fat utilization was 1753 kJ and 1857 kJ in the high-intensity first and low-intensity first trials respectively (t 6 = -0.76, P = 0.24). Our findings suggest that changing the temporal placement of higher-intensity work within a low-intensity exercise session has a significant effect on total energy expenditure but not on the rate of fat oxidation.     

A qualitative analysis of context-aware ubiquitous learning environments using Bluetooth beacons

The use of Bluetooth Low Energy (BLE) beacons is becoming widespread for context-aware learning environments. This technology can be used in indoor and outdoor settings such as museums, shops, home and schools in order to identify the location of learners and their contexts. Specifically, in the constructivist view of learning, learners can use such sensing technology for constructing knowledge and experiencing learning at any time, anywhere. However, exploration of such technology has been limited in the constructivist context-aware ubiquitous learning (U-learning) literature. For this purpose, the authors evaluated two android-based U-learning applications: one was an outdoor learning environment in a garden, the other was about locating books in a library. The applications were implemented and tested with school and university students. The qualitative results are presented in this article, and show how such sensing technology is promising for both pedagogical environments.     

Conservation laws for energy and momentum in curved spaces

In arbitrary Riemannian 4-spaces, continuity equations are constructed which could be interpreted as conservation laws for the energy and momentum of the gravitational field. Special attention is given to general relativity to obtain, of natural manner, the pseudotensors of Einstein, Landau-Lifshitz, Mller, Goldberg and Stachel, and also the conservation equations of Komar, Trautman, DuPlessis and Moss.     

动态的哈勃常数与弦(以太)的一些探讨

在遥远的河外星系,由于光子到达地球需要很长的时间,这其间使得到达地球观测点的光波发生红移,该红移遵从哈勃定律,所以被称为哈勃红移.然而宇宙的膨胀使得宇宙的密度逐渐下降,哈勃常数也在不断的减小,即哈勃常数是动态变化的.在研究宇宙尺度下的光谱红移时,哈勃红移是按动态的哈勃常数进行的.     

新能源视角下欧盟2011年节能与能效立法措施评析

能源效率被欧盟看作最大的新能源资源.欧盟节能与能源效率立法涉及终端使用能效、建筑物能源表现、用能产品标签、热电联产和用能产品的生态设计五大方面.2011年欧盟提出新的能源效率立法提案,体现了对分散在各领域的节能与能源效率法律政策进行整合的趋势,并采取有法律约束力的行动,促使成员国在节能和能源效率方面执行更为有效的措施.中国应借鉴欧盟经验,将能源供应安全纳入立法目标,协调发展节能与能效法律政策,并增强其执行力.     

论《能源宪章条约》的过境争端解决机制

《能源宪章条约》(Energy Charter Treaty,简称ECT)中的能源过境制度是该条约最引人注目的,它的建立存在着历史基础和现实基础.ECT的第7条第7款和《有关过境争端的调解行为规则》构成过境争端解决机制的主要内容.该机制具有创新性,但同时也带有无法避免的局限性,对该机制进行改革势在必行.目前中国在解决能源过境争端时,可以借鉴ECT的过境争端解决机制,但同时也要考虑过境争端中的政治因素.     

合同能源管理在图书馆节能减排工作中的应用研究

可持续发展和社会责任要求图书馆不仅要宣传节能减排,还要切实做好自身的能源管理工作,将节能减排落到实处。能源管理的意识薄弱、制度缺失、经费不足及技术条件薄弱已经成为图书馆践行节能减排的显著障碍。因此,图书馆应引入基于市场机制的合同能源管理模式,以推动图书馆节能减排工作的开展,有效降低图书馆运行能耗,在减轻能源负担的同时探索出一条绿色、低碳的可持续发展之路。