Does maturation influence neuromuscular performance and muscle damage after competitive match-play in youth male soccer players?

Abstract

Poor neuromuscular control and fatigue have been proposed as a risk factor for non-contact injuries especially around peak height velocity (PHV). This study explored the effects of competitive soccer match-play on neuromuscular performance and muscle damage in male youth soccer players. 24 youth players aged 13-16y were split into a PHV group (?0.5 to 0.5y) and post PHV group (1.0–2.5y) based on maturity off-set. Leg stiffness, reactive strength index (RSI), muscle activation, creatine kinase (CK), and muscle soreness were determined pre and post a competitive soccer match. Paired t-tests were used to explore differences pre and post competitive match play and independent sample t-tests for between groups differences for all outcome measures. There was no significant fatigue-related change in absolute and relative leg stiffness or muscle activation in both groups, except for the gastrocnemius in the post PHV group. RSI, CK and perceived muscle soreness were significantly different after soccer match-play in both groups with small to large effects observed (ES:0.41–2.82). There were no significant differences between the groups pre match-play except for absolute and relative leg stiffness (P?<?0.001; ES?=?1.16 and 0.63 respectively). No significant differences were observed in the fatigue related responses to competitive match play between groups except for perceived muscle soreness. The influence of competitive match-play on neuromuscular function and muscle damage is similar in male youth around the time of PHV and those post-PHV indicating that other factors must contribute to the heightened injury risk around PHV.     

Does a water-training macrocycle really create imbalances in swimmers' shoulder rotator muscles?

Abstract

The continuous execution of swimming techniques may cause muscle imbalances in shoulder rotators leading to injury. However, there is a lack of published research studies on this topic. The aim of this study was to analyze the influence of a competitive swim period on the shoulder rotator–cuff balance in young swimmers. A randomized controlled pretest–posttest design was used, with two measurements performed during the first macrocycle of the swimming season (baseline and 16 weeks). Twenty-seven young male swimmers (experimental group) and 22 male students who were not involved in swim training (control group) with the same characteristics were evaluated. Peak torque of shoulder internal and external rotators was assessed. Concentric action at 1.04 rad s^?1 (3 repetitions) and 3.14 rad s^?1 (20 repetitions) was measured using an isokinetic dynamometer (Biodex System 3). External/internal rotators strength ratios were also obtained. For both protocols, there were significant training effects on internal rotator strength and external/internal rotator ratios (p ≤ .05). This trend was the same for both shoulders. Within-group analysis showed significant changes from baseline to 16 weeks for internal rotators strength and unilateral ratios of the experimental group. Swimmers' internal rotator strength levels increased significantly. In contrast, a significant decrease of the unilateral ratios was observed. Findings suggest that a competitive swim macrocycle leads to an increase in muscular imbalances in the shoulder rotators of young competitive swimmers. Swimming coaches should consider implementing a compensatory strength-training program.     

Whole-body vibration as a method of recovery for soccer players

Abstract

The aim of this study was to determine whether superimposed whole-body vibration could improve the recovery-related effects of a traditional cool-down in high-level soccer players. Sixteen high-level junior soccer players performed a repeated-sprint ability test, after which they performed a traditional cool-down, with (experimental group) or without (control group) superimposed whole-body vibration. Functional recovery was measured through vertical jump height and maximal voluntary isometric force in leg-extension. The repeated-sprint ability test induced increases (from 161 to 215%; P<0.05) in muscle pain measured by visual analogue scale in the control group only. Vertical jump height was recovered earlier with than without whole-body vibration (24 h after the repeated-sprint ability test; P<0.05). The results of this study demonstrate that whole-body vibration in combination with a traditional cool-down can reduce perceived muscle pain and enhance recovery after a soccer-specific exercise.     

Change-of-direction,speed and jump performance in soccer players: a comparison across different age-categories

ABSTRACT

This study examined the age-specific development of vertical jump height, straight and change-of-direction (COD) speed, and COD deficit in one-hundred and eighty-two elite soccer players from different age-categories (U15, U17, U20, and Senior). All participants were players of two distinct clubs and were undertaking different training routines, as planned by their technical staff members. For this purpose, the soccer players performed: (1) squat and countermovement jumps; (2) a maximal 20-m linear sprint speed test, and (3) the Zigzag COD test. The magnitude-based inference approach and standardized differences were used to compare the age-groups. Sprint speed at longer distances (20-m) increased progressively across the age-ranges. In contrast, speed and acceleration performances at shorter distances (5-m) were better in U15 than in the other age-categories. The COD speed did not change throughout the younger categories but presented a meaningful decrease in the Senior category. Surprisingly, despite the progressive increase in volume and intensity of neuromuscular training from younger to older categories, the COD deficit presented a gradual increase across the age-groups. It is possible that simple modulation of the strength-power training program during the maturation process is not sufficient to produce faster adult players with enhanced ability to change direction. Therefore, coaches are strongly encouraged to implement specific COD training practices to tolerate braking at increasing running speeds and appropriate volume and intensity of soccer specific training throughout the players’ specialization process.     

Evaluation of treatment effect estimates in single‐case experimental research: comparison of twelve overlap methods and visual analysis

The purpose of this study was to compare 12 commonly‐used nonoverlap methods with each other and with the results of visual analysis. Data were obtained from 25 studies focused on embedded instruction and schema‐based instruction and included a total of 101 graphs. Treatment effect estimates using 12 nonoverlap methods were calculated for each graph by hand or using an online calculator. Five experts conducted visual analysis of each graph. Results showed that strong agreements existed between visual analysis and PND, Tau_NOVLAP and Tau‐U when raw data were analysed, and PND, PNCD and PEM‐T when categorised data were analysed. Of the 12 methods investigated, PND had the highest agreement rate with visual analysis, followed by PEM‐T, PAND, PNCD, IRD, NAP and Tau_NOVLAP. Overall, visual analysis appeared to be more conservative, as most nonoverlap methods overestimated the treatment effect. Additional research is needed to replicate and potentially validate the findings of this study.     

瓦楞纸箱结构设计及其尺寸计算方法

瓦楞纸箱在物流和商流中发挥着巨大的作用,但其本身的结构设计困扰着大多数设计者,基于此,以实际生产中实际案例为项目,通过分析和制作工作项目为线索,参考国家标准GB/T 6543-2008,较为翔实地进行纸箱箱型、排列方式、内尺寸、制作尺寸、外尺寸的选择和计算,并以CAD为依托,完成结构图绘制和立体图成型,解决了纸箱结构设计和尺寸计算问题,具有一定的理论和实践研究意义。     

How Important Is Private Higher Education in Europe? A Regional Analysis in Global Context1

The importance of private higher education (PHE) is increasingly clear globally. But does Europe fit the global generalisation? This question can be assessed with reference to two major considerations: the size of PHE and the degree of private-public difference. The growth of PHE in Europe has been delayed and limited compared to that in most of the world, though still significant. For the 27-member European Union, the PHE share is best put at 12%, with a modestly higher share for Europe more broadly defined. Europe's PHE share is thus less than half that of the global share. The regional share is considerably higher in Eastern than in Western Europe. In terms of distinctiveness, European PHE differs from public higher education in important respects that reflect world patterns. Inter-sectoral differences are decisive in finance. Though less quantifiable, they appear fundamental albeit blurred in some but not all aspects of governance and activities. Blurring in activities, governance, and even finance occurs through changes within both sectors, especially through partial privatisation within the public sector. Still, Europe's private sector is far from simply isomorphic to the public sector. Considering together size and distinctiveness, a reasonable assessment is that PHE has moderate and increased importance in Europe.     

Temporal trends in the sit-ups performance of 9,939,289 children and adolescents between 1964 and 2017

ABSTRACT

We estimated international/national temporal trends in sit-ups performance for children and adolescents, and examined relationships between national trends in sit-ups performance and national trends in health-related/sociodemographic indicators. Data were obtained by systematically searching studies reporting on temporal trends in sit-ups performance for apparently healthy 9–17 year-olds, and by examining nationally representative fitness datasets. Trends at the country-sex-age level were estimated by sample-weighted regression models relating the testing year to mean sit-ups performance. International/national trends were estimated by a post-stratified population-weighting procedure. Pearson’s correlations quantified relationships between national trends in sit-ups performance and national trends in health-related/sociodemographic indicators. A total of 9,939,289 children and adolescents from 31 countries/special administrative regions between 1964 and 2017 collectively showed a large improvement of 38.4% (95% CI: 36.8 to 40.0) or 7.1% per decade (95% CI: 6.8 to 7.4). Large international improvements were experienced by all age and sex groups, with the rate of improvement slowing from 1964 to 2000, stabilizing near zero until 2010, before declining. Trends differed between countries, with national trends in vigorous physical activity a strong, positive correlate of national trends in sit-ups performance. More sit-ups data are needed from low- and middle-income countries to better monitor trends in muscular fitness.     

罚球感知能力训练对罚球准确性影响的实验研究

对体育院系篮球专修学生罚球感知能力进行罚球技术的教学实验研究,结果显示,实验组通过罚球专门性训练在罚球准确性和优势手肌肉用力感和手动稳定性罚球感知能力指标上与对照组相比均有显著性的差异.说明罚球专门性训练手段在提高罚球准确性和加速专门化感知觉的形成上具有一定的积极作用,因此,有针对性地对优势手肌肉用力感和手动稳定性所设计的练习方法可以避免罚球教学训练过程中的盲目性,从而有效地提高罚球准确性.