Renal lactate elimination is maintained during moderate exercise in humans

Reduced hepatic lactate elimination initiates blood lactate accumulation during incremental exercise. In this study, we wished to determine whether renal lactate elimination contributes to the initiation of blood lactate accumulation. The renal arterial-to-venous (a-v) lactate difference was determined in nine men during sodium lactate infusion to enhance the evaluation (0.5 mol x L(-1) at 16 ± 1 mL x min(-1); mean ± s) both at rest and during cycling exercise (heart rate 139 ± 5 beats x min(-1)). The renal release of erythropoietin was used to detect kidney tissue ischaemia. At rest, the a-v O(2) (CaO(2)-CvO(2)) and lactate concentration differences were 0.8 ± 0.2 and 0.02 ± 0.02 mmol x L(-1), respectively. During exercise, arterial lactate and CaO(2)-CvO(2) increased to 7.1 ± 1.1 and 2.6 ± 0.8 mmol x L(-1), respectively (P < 0.05), indicating a -70% reduction of renal blood flow with no significant change in the renal venous erythropoietin concentration (0.8 ± 1.4 U x L(-1)). The a-v lactate concentration difference increased to 0.5 ± 0.8 mmol x L(-1), indicating similar lactate elimination as at rest. In conclusion, a -70% reduction in renal blood flow does not provoke critical renal ischaemia, and renal lactate elimination is maintained. Thus, kidney lactate elimination is unlikely to contribute to the initial blood lactate accumulation during progressive exercise.     

Prediction of segmental lean mass using anthropometric variables in young adults

The aim of the present study was to develop and cross-validate anthropometrical prediction equations for segmental lean tissue mass (SLM). One hundred and seventeen young healthy Caucasians (67 men and 50 women; mean age: 31.9 ± 10.0 years; Body Mass Index: 24.3 ± 3.2 kg · m(-2)) were included. Body mass (BM), stretch stature (SS), 14 circumferences (CC), 13 skinfolds (SF) and 4 bone breadths (BB) were used as anthropometric measurements. Segmental lean mass of both arms, trunk and both legs were measured by dual energy X-ray absorptiometry as the criterion method. Three prediction equations for SLM were developed as follows: arms = 40.394(BM) + 169.836(CCarm-tensed) + 399.162(CCwrist) - 85.414(SFtriceps) - 39.790(SFbiceps) - 7289.190, where Adj.R (2) = 0.97, P < 0.001, and standard error of estimate (SEE) = 355 g;trunk = 181.530(BM) + 155.037(SS) + 534.818(CCneck) + 175.638(CCchest) - 88.359(SFchest) - 147.232(SFsupraspinale) - 46522.165, where Adj.R(2) = 0.97, P < 0.001, and SEE = 1077g; and legs = 55.838(BM) + 88.356(SS) + 235.579(CCmid-thigh) + 278.595(CCcalf) + 288.984(CCankle) - 84.954(SFfront-thigh) - 53.009(SFmedial calf) - 28522.241, where Adj.R (2) = 0.96, P < 0.001, and SEE = 724 g. Cross-validation statistics showed no significant differences (P < 0.05) between observed and predicted SLM. Root mean squared errors were smallest for arms (362 g), followed by legs (820 g) and trunk (1477 g). These new prediction equations allow an accurate estimation of segmental lean mass in groups of young adults, but estimation errors of 8 to 14% can occur in certain individuals.     

Interpreting the Dispositional Flow Scale-2 scores: a pilot study of latent class factor analysis

The present study examined the extent to which scores on the Dispositional Flow Scale-2 (DFS-2) could differentiate individuals who frequently experience flow characteristics in physical activity from those who do not. A total of 993 participants completed the Japanese version of the DFS-2. Latent class factor analysis (LCFA), which combines the strengths of both latent class analysis and factor analysis, was conducted on the DFS-2 responses. Six classes were identified through a series of LCFAs and the patterns of the item-average scores for the nine flow attributes were found to be parallel among these classes. The top two and bottom two classes (19.3% and 13.4% of the whole sample) were considered the groups who experience flow characteristics frequently and seldom, respectively. These results indicated that individuals who often experience flow attributes in physical activity could be differentiated from those who do not based on their DFS-2 scores.     

浅谈网球运动中的放松活动

本文运用文献资料法、归纳演绎法等,阐述了网球运动中的放松训练的作用机理,在此基础上从多个角度剖析了放松训练对网球运动初学者所产生的多方面的积极影响,指出网球练习中如何运用放松训练来达到更好的学习效果,以及在练习过程中如何将心理状态调整到最佳的对策与方法。为网球学习者在训练时达到各个环节的充分放松;迅速掌握网球基本技术和获得较高运动水平提供理论参考。     

网球运动员反手击球力量的训练方法研究

无论是专业的网球运动员还是业余的网球发烧友,都会有同一个感觉——反手的击球动作相比于正手击球动作要难提高。尤其是在一些业余的比赛中,反手往往成为对方攻击的主要位置。如何提高反手水平成了广大同球爱好者迫切希望解决的问题。本文通过对网球技术中反手技术的深入分析,在符合人体生理规律的基础上提出一些反手技术的辅助训练方法,可以有效提高国球运动者反手击球水平。     

Playing the game: Psychology textbooks speak out about love

Starting in 1958, Harry Harlow published numerous research papers analyzing the emotional and social development of rhesus monkeys. This essay examines the presentation of Harlow's work in introductory psychology textbooks from 1958 to 1975, focusing on whether the textbooks erased the process of research, presented results without hedging, and provided a uniform account of Harlow's work and results. It argues that many textbooks were not passive vehicles of knowledge transmission; instead, they played a role similar to articles of meta-analysis and literature reviews.     

Predicting the past: ancient eclipses and Airy, Newcomb, and Huxley on the authority of science

Greek historical accounts of ancient eclipses were an important, if peculiar, focus of scientific attention in the nineteenth century. Victorian-era astronomers tried to correct the classical histories using scientific methods, then used those histories as data with which to calibrate their lunar theories, then rejected the histories as having any relevance at all. The specific dating of these eclipses--apparently a simple exercise in celestial mechanics--became bound up with tensions between scientific and humanistic approaches to the past as well as with wider social debates over the power and authority of science in general. The major figures discussed here, including G. B. Airy, Simon Newcomb, and T. H. Huxley, argued that the critical question was whether science could speak authoritatively about the past. To them, the ability of science to talk about the past indicated its power to talk about the future; it was also the fulcrum of fierce boundary disputes among science, history, and religion.     

Movement variability in the golf swing

Traditionally, golf biomechanics has focused upon achieving consistency in swing kinematics and kinetics, whilst variability was considered to be noise and dysfunctional. There has been a growing argument that variability is an intrinsic aspect of skilled motor performance and plays a functional role. Two types of variability are described: 'strategic shot selection' and 'movement variability'. In 'strategic shot selection', the outcome remains consistent, but the swing kinematics/kinetics (resulting in the desired ball flight) are free to vary; 'movement variability' is the changes in swing kinematics and kinetics from trial to trial when the golfer attempts to hit the same shot. These changes will emerge due to constraints of the golfer's body, the environment, and the task. Biomechanical research has focused upon aspects of technique such as elite versus non-elite kinematics, kinetics, kinematic sequencing, peak angular velocities of body segments, wrist function, ground reaction forces, and electromyography, mainly in the search for greater distance and clubhead velocity. To date very little is known about the impact of variability on this complex motor skill, and it has yet to be fully researched to determine where the trade-off between functional and detrimental variability lies when in pursuit of enhanced performance outcomes.     

Pathways to mathematics: longitudinal predictors of performance

A model of the relations among cognitive precursors, early numeracy skill, and mathematical outcomes was tested for 182 children from 4.5 to 7.5 years of age. The model integrates research from neuroimaging, clinical populations, and normal development in children and adults. It includes 3 precursor pathways: quantitative, linguistic, and spatial attention. These pathways (a) contributed independently to early numeracy skills during preschool and kindergarten and (b) related differentially to performance on a variety of mathematical outcomes 2 years later. The success of the model in accounting for performance highlights the need to understand the fundamental underlying skills that contribute to diverse forms of mathematical competence.     

Reading minds: the relation between children's mental state knowledge and their metaknowledge about reading

The relation between children's mental state knowledge and metaknowledge about reading was examined in 2 studies. In Study 1, 196 children (mean age = 9 years) were tested for verbal ability (VA), metaknowledge about reading, and mental state words in a story task. In Study 2, the results of Study 1 were extended by using a cross-lagged design and by investigating older children (N = 71, mean ages = 10 years at Time 1 and 11 years at Time 2) for mental state knowledge, metaknowledge about reading, and VA. Results showed a significant relation between early cognitive (but not emotion) mental state knowledge and later metaknowledge about reading, controlling for VA. Results suggest close links between different aspects of children's knowledge about the mind.