In vivo behavior of vastus lateralis muscle during dynamic performances

Length changes in vastus lateralis fascicles were measured in vivo using ultrasonography during one-legged squat jumps (SJ), counter movement jumps (CMJ), and drop jumps (DJ) in the sledge apparatus (n = 9). Patellar tendon forces were recorded simultaneously with an optic fiber technique from 4 subjects. Fascicle length changes were compared with muscletendon unit length changes calculated from kinematic recordings. In general, the tendomuscular and fascicle length changes demonstrated similar patterns. During SJ the fascicles showed shortening throughout the action while during CMJ and DJ they underwent stretch-shortening cycle. In DJ greater muscular activity in braking phase.     

Morphology of the deltoid muscles in elite tennis players

Abstract

The aim of this study was to examine the deltoid muscle properties of the dominant and non-dominant arm of Greek professional male tennis players. Eight male tennis players (mean age 22.0 years, s = 3.2) were subjected to biopsy of the deltoid muscle of both arms. Adenosine triphosphate (ATPase) histochemistry and myosin heavy chain (MHC) composition were performed on the samples with homogenate electrophoresis. No significant differences were observed in the percentage of types I, IIa, IIab, and IIb muscle fibres between the deltoid muscles of the two arms. Types I, IIa, and IIx muscle fibres of the dominant and non-dominant deltoid muscles did not differ significantly for MHC isoform composition. Type IIab muscle fibres showed a similar cross-sectional area (CSA) percentage distribution between the two arms. The CSA percentage for types I, IIa, and IIb muscle fibers did not differ significantly between the dominant and the non-dominant arm. We conclude therefore that regular tennis training probably does not lead to any significant changes in the muscle fibre types of the dominant and non-dominant arms of elite tennis players.     

Morphology of the deltoid muscles in elite tennis players

The aim of this study was to examine the deltoid muscle properties of the dominant and non-dominant arm of Greek professional male tennis players. Eight male tennis players (mean age 22.0 years, s = 3.2) were subjected to biopsy of the deltoid muscle of both arms. Adenosine triphosphate (ATPase) histochemistry and myosin heavy chain (MHC) composition were performed on the samples with homogenate electrophoresis. No significant differences were observed in the percentage of types I, IIa, IIab, and IIb muscle fibres between the deltoid muscles of the two arms. Types I, IIa, and IIx muscle fibres of the dominant and non-dominant deltoid muscles did not differ significantly for MHC isoform composition. Type IIab muscle fibres showed a similar cross-sectional area (CSA) percentage distribution between the two arms. The CSA percentage for types I, IIa, and IIb muscle fibers did not differ significantly between the dominant and the non-dominant arm. We conclude therefore that regular tennis training probably does not lead to any significant changes in the muscle fibre types of the dominant and non-dominant arms of elite tennis players.     

篮球、手球、足球运动员体成分及肌肉力量的比较分析

目的:对篮球、手球、足球运动员的身体成分和肌肉力量进行比较分析,探讨三大球运动员身体素质的特点与差异,为运动训练以及运动员科学选材提供理论参考.方法:研究对象均为篮球、足球、手球二级以上专业运动员,均为男性,身高、体重、年龄和运动年限无明显差异,对研究对象进行体成分和肌肉力量测试及比较分析.结果:篮球组与手球组腹下脂肪比率、基础代谢、肥胖程度、BMI以及细胞液都有非常显著性差异(P＜0.01);篮球组与足球组之间下肢和腹下脂肪与体重比存有差异性(P＜0.05),胸下脂肪与体重比存有非常显著性差异(P＜0.01);手球运动员与足球运动员之间肥胖程度、BMI、细胞液和基础代谢均有非常显著性差异(P＜0.01);在上下肢力量方面篮球运动员与手球和足球运动员存有非常显著性差异(P＜0.01).结论:手球运动员在身高、体重、脂肪比率、BMI、细胞量、蛋白质、无机盐、细胞液方面都明显高于篮球和足球运动员;篮球运动员在力量方面比较占据优势;足球运动员身材相对较小,在体脂比率、BMI以及上下肢力量方面低于篮球和手球运动员.     

女子手球运动员肩关节屈伸肌群的等速测试与分析

目的：对广东省女子手球队运动员肩关节屈伸肌群的力矩特征进行研究,为运动队的训练和科研提供参考。方法：运用CON-TREX人体肌力评估和训练系统并选取60°/s和240°/s对运动员两侧肩关节进行等速测试。结果：肩关节伸肌峰力矩和相对峰力矩值均大于屈肌;受试者肩关节屈伸肌峰力矩比值大都在60%-90%之间;大部分队员肩关节同名肌力矩差值在10%以内。结论：广东女子手球运动员两侧肩关节伸肌群力量大于屈肌;右侧肩关节伸肌群的力量大于左侧;在两种不同测试速度下,受试者肩关节屈伸肌峰力矩比值在合理范围内;大部分队员两侧肩关节伸屈肌力量保持平衡。     

The role of community in the development of elite handball and football players in Denmark

The primary purpose of this study was to investigate the effect of the place of early development in a sample of Danish male elite and youth handball and football players. The sample included 366 handball and football players from the elite Danish league in the season 2011–2012 and a comparison sample of youth players under the age of 12 from 2003, including 147,221 football and 26,290 handball players. Odds ratio analysis showed that both population size and density significantly affected the proportional number of youth players per community and the odds of athletes reaching an elite level in football and handball. The odds for youth player registrations in both handball and football increased in rural in contrast to urban communities. However, elite football players primarily came from communities of high density (>1000 pop./km²), whereas elite handball players primarily came from less densely populated communities (100 to <250 pop./km²). Furthermore, there seems to be a relation between representation of elite and talent clubs in different communities and the probability of becoming an elite player in both sports. The limited number of elite players in both sports from rural communities may be due to national talent development strategies that do not incorporate development support for clubs in rural areas. Additionally, the results of the study clearly suggest the need to include the youth player population to advance research findings in birthplace effect studies.     

Gender differences in the kinematics and ball velocity of overarm throwing in elite team handball players

The aim of this study was to investigate the throwing velocity and kinematics of overarm throwing in team handball of elite female and male handball players. Kinematics and ball velocity of a 7 metre-throw in eleven elite male (age 23.6 ± 5.2 yr, body mass 87.0 ± 6.8 kg, height 1.85 ± 0.05 m) and eleven elite female (age 20.3 ± 1.8 yr, body mass 69.9 ± 5.5 kg, height 1.75 ± 0.05 m) team handball players were recorded. The analysis consisted of maximal joint angles, angles at ball release, maximal angular velocities of the joint movements, and maximal linear velocities of the distal endpoints of segments and their timing during the throw. The ball release velocity of the male handball players was significantly higher than the females (21.1 vs. 19.2 m · s(-1); p < 0.05). No major differences in kinematics were found, except for the maximal endpoint velocities of the hand and wrist segment, indicating that male and female handball players throw with the same technique. It was concluded that differences in throwing velocity in elite male and female handball players are generally not the result of changes in kinematics in the joint movements.     

Muscle morphology of the vastus lateralis is strongly related to ergometer performance,sprint capacity and endurance capacity in Olympic rowers

Rowers need to combine high sprint and endurance capacities. Muscle morphology largely explains muscle power generating capacity, however, little is known on how muscle morphology relates to rowing performance measures. The aim was to determine how muscle morphology of the vastus lateralis relates to rowing ergometer performance, sprint and endurance capacity of Olympic rowers. Eighteen rowers (12♂, 6♀, who competed at 2016 Olympics) performed an incremental rowing test to obtain maximal oxygen consumption, reflecting endurance capacity. Sprint capacity was assessed by Wingate cycling peak power. M. vastus lateralis morphology (volume, physiological cross-sectional area, fascicle length and pennation angle) was derived from 3-dimensional ultrasound imaging. Thirteen rowers (7♂, 6♀) completed a 2000-m rowing ergometer time trial. Muscle volume largely explained variance in 2000-m rowing performance (R² = 0.85), maximal oxygen consumption (R² = 0.65), and Wingate peak power (R² = 0.82). When normalized for differences in body size, maximal oxygen consumption and Wingate peak power were negatively related in males (r = ?0.94). Fascicle length, not physiological cross-sectional area, attributed to normalized peak power. In conclusion, vastus lateralis volume largely explains variance in rowing ergometer performance, sprint and endurance capacity. For a high normalized sprint capacity, athletes may benefit from long fascicles rather than a large physiological cross-sectional area.     

Responses of low and high compression during recovery after repeated sprint training in well-trained handball players

The aim of the study was to investigate the effects of wearing various levels of compression following repeated and exhausting sprint exercise on variables related to recovery. Twelve well-trained handball players performed three sessions of repeated and exhausting sprint exercise (30?×?30m). Directly after each session the participants wore tights extending from below the hip to the foot with either 0, 10, or 25?mm?Hg of compression onto the thigh and calf muscles. 48?h after the training session all participants performed 5?×?30m sprints and counter movement jumps. Before, directly after, 24?h, and 48?h after the training session venous blood samples were drawn for the determination of creatine kinase (CK), urea, C-reactive protein (CRP). At the same time points, subjective ratings of the Acute Recovery and Stress Scale (ARSS) questionnaires were obtained. The results for plasma concentrations of CK and urea showed ‘likely’ to ‘very, very likely’ beneficial effects for compression garments exerting 10?mm?Hg of compression (p?=?0.06–1.0). With regard to sprint and jump performance no differences were evident between 0, 10, and 25?mm?Hg (p?=?0.07–1.0). In addition, subjective scores from the ARSS did not differ between conditions over time (p?>?0.05). We conclude that the application of 10?mm?Hg leg compression compared to 0 and 25?mm?Hg of compression during 48?h of recovery from repeated and exhausting sprints lowered the plasma concentrations of CK and urea with no improvements in recovery for performance.     

Functional shoulder ratios with high velocities of shoulder internal rotation are most sensitive to determine shoulder rotation torque imbalance: a cross-sectional study with elite handball players and controls

The aim of the present study was to determine which approach to calculating shoulder ratios is the most sensitive for determining shoulder torque imbalance in handball players. Twenty-six participants (handball athletes, n = 13; healthy controls, n = 13) performed isokinetic concentric and eccentric shoulder internal rotation (IR) and external rotation (ER) assessment at 60, 180 and 300°/s. We used eight approaches to calculating shoulder ratios: four concentric (i.e. concentric ER torque divided by concentric IR torque), and four functional (i.e. eccentric ER torque divided by concentric IR torque) at the velocities of 60, 180 and 300°/s for both IR and ER, and combining 60°/s of ER and 300°/s of IR. A three factorial ANOVA (factors: shoulder ratios, upper limb sides, and groups) along with Tukey’s post-hoc analysis, and effect sizes were calculated. The findings suggested the functional shoulder ratio combining 60°/s of ER and 300°/s of IR is the most sensitive to detect differences between upper limbs for handball players, and between players and controls for the dominant side. The functional shoulder ratio combining 60°/s of ER with 300°/s of IR seems to present advantages over the other approaches for identifying upper limb asymmetries and differences in shoulder torque balance related to throwing.     

Anthropometry and body composition of female handball players according to competitive level or the playing position

Abstract

Anthropometry and body composition were investigated in 43 female handball players from the Italian championships, grouped according to their competitive level (elite vs. sub-elite) or their playing position [goalkeeper (n = 7), back (n = 14), wing (n = 18), or pivot (n = 4)]. The anthropometry consisted of several circumferences, lengths, widths, and skinfold measurement at six sites; the regional and total body compositions were assessed by means of dual-energy X-ray absorptiometry (DXA). One-way ANOVA was used for statistical analysis, with a Bonferroni post-hoc test where needed. The results showed that elite players have significantly lower percentages of fat and higher bone mineral content than sub-elite as well as a clear tendency to accrue more lean mass, especially in upper limbs. Overall, the physical characteristics and body composition of handball players in Italy compared unfavourably with those in other countries, suggesting a need for improved selection and training. When playing position was included in the analysis of the whole group of handball players (n = 43) significant differences were found between the stature, mass, body mass index (BMI), several skinfolds, circumferences and lengths, and total body mineral mass, lean mass and fat mass of players in different positions. Post-hoc analysis suggests that players on the wing and in goalkeeper positions differed most from one another. These findings confirm and expand on previous data about the presence of anthropometric differences within playing positions in handball.     

The effect of low back pain on trunk muscle size/function and hip strength in elite football (soccer) players

ABSTRACT

Low back pain (LBP) is a common problem in football (soccer) players. The effect of LBP on the trunk and hip muscles in this group is unknown. The relationship between LBP and trunk muscle size and function in football players across the preseason was examined. A secondary aim was to assess hip muscle strength. Twenty-five elite soccer players participated in the study, with assessments conducted on 23 players at both the start and end of the preseason. LBP was assessed with questionnaires and ultrasound imaging was used to assess size and function of trunk muscles at the start and end of preseason. Dynamometry was used to assess hip muscle strength at the start of the preseason. At the start of the preseason, 28% of players reported the presence of LBP and this was associated with reduced size of the multifidus, increased contraction of the transversus abdominis and multifidus muscles. LBP decreased across the preseason, and size of the multifidus muscle improved over the preseason. Ability to contract the abdominal and multifidus muscles did not alter across the preseason. Asymmetry in hip adductor and abductor muscle strength was found between players with and without LBP. Identifying modifiable factors in players with LBP may allow development of more targeted preseason rehabilitation programmes.     

间歇低氧训练对SD大鼠心肌肌球蛋白重链表达的影响

目的:观察在间歇低氧及游泳运动的影响下,SD大鼠心肌细胞肌球蛋白重链α-MHC、β-MHC两种异构型表达的变化,探讨间歇低氧训练对心肌功能影响的可能分子机制.方法:将128只SD大鼠随机分成对照组、间歇低氧训练组、游泳训练组及间歇低氧+游泳训练组,经过4周的训练,采用SDS-PAGE法观察SD大鼠心肌细胞肌球蛋白重链α-MHC、β-MHC表达的变化. 结果:间歇低氧及游泳训练可引起α-MHC表达不同程度的上调,同时β-MHC表达不同程度的下调.结论:在间歇低氧及运动性机械刺激作用的过程中,心肌细胞通过上调α-MHC和下调β-MHC的表达,来适应环境氧分压降低的变化和运动刺激的作用.     

耐力训练对肌球蛋白重链的影响及MyoD、Myogenin的调控作用

为了解耐力训练对肌球蛋白重链(MHC)组成及生肌调节因子MyoD和Myogenin表达的影响,探讨MyoD和Myogenin表达与MHC转换的关系,选用雄性SD大鼠20只,随机分成安静对照组(10只)和耐力训练组(10只)。耐力训练组进行跑台练习:跑台坡度10°,跑速20m/min,每天1次,每次1h,每周训练6d,28d后取浅层胫前肌。SDS-PAGE方法测定MHCⅠ、Ⅱa、Ⅱx、Ⅱb蛋白组成;RT-PCR测定MHCs及MyoD、Myogenin mRNA表达。结果:耐力训练没有改变MHCs蛋白表达,耐力训练后Ⅱx-MHC mRNA表达显著减少(P<0.05);耐力训练使MyoD、Myogenin mRNA均显著下降。结果说明耐力训练使快型MHC基因表达减少;快型MHCⅡx减少可能与MyoD表达下降有关,MyoD和Myogenin可能参与MHC表达的调节。     

Multivariate isokinetic asymmetry of the knee and shoulder in elite volleyball players

Abstract

Muscle strength asymmetries have been investigated in athletes under the assumption of their connection to functional discrepancies and injuries. In volleyball, which is a highly asymmetric sport, this assumption becomes a well established research hypothesis. Given the almost complete lack of scientific evidence on this hypothesis, the present study focused on the detailed multivariate quantification of muscle asymmetries in offensive volleyball players. Twenty-four elite athletes (age 24.71±4.44 years, weight 84.62±6.24, height 190.08±5.58) were tested for concentric isokinetic muscle strength (a) of the internal and external rotators of the shoulder and (b) of the quadriceps and hamstrings of the knee at 60^o/s. Significant multivariate results were found for absolute (Max-Min) asymmetry in the upper (Hotteling's T ²=8.801, F=7.447, P=0.001) and the lower limbs (Hotteling's T ²=16.382, F=13.862, P=0.000), for fluctuating asymmetry (Dominant-Non Dominant) in the upper limbs (Hotteling's T ²=5.584, F=4.296, P=0.013) and for directional asymmetry (Left-Right) in the lower limbs (Hotteling's T ²=3.593, F=3.041, P=0.036). It appears that the upper and lower limbs of offensive volleyball players present significant composite muscle strength asymmetries, which should be taken into consideration in training and rehabilitation.     

Kinematic differences of elite and high-performance tennis players in the cross court and down the line forehand

This study identified and compared the full body kinematics of different skill levels in the forehand groundstroke when balls were hit cross court and down the line. Forty-three three-dimensional retro-reflective marker trajectories of six elite and seven high-performance players were recorded using an eight-camera 400 Hz, Vicon motion analysis system. The six highest horizontal velocity forehands with reliable kinematics of all participants were analysed for each specific situation (a total of 156 analysed shots). Significant differences (p < 0.01) and large effect sizes were observed between elite and high-performance players in linear velocity of the shoulder (2.0 vs. 1.2 m/s), angular velocity of the pelvis (295 vs. 168 °/s), and angular velocity of the upper trunk (453 vs. 292 °/s) at impact. The elite group showed a tendency towards higher racquet velocities at impact (p < 0.05). No significant differences were found in angular displacement of the racquet, hip alignment, or shoulder alignment at the completion of the backswing; nor did angular displacement vary significantly at impact. Irrespective of the group, different shoulder, hip, and racquet angles were found at impact, depending on the situation. The results should assist coaches when striving to improve their players' forehand.     

Test-retest reliability and agreement of the SPI-Questionnaire to detect symptoms of digital ischemia in elite volleyball players

The Shoulder posterior circumflex humeral artery Pathology and digital Ischemia – questionnaire (SPI-Q) has been developed to enable periodic surveillance of elite volleyball players, who are at risk for digital ischemia. Prior to implementation, assessing reliability is mandatory. Therefore, the test-retest reliability and agreement of the SPI-Q were evaluated among the population at risk.

A questionnaire survey was performed with a 2-week interval among 65 elite male volleyball players assessing symptoms of cold, pale and blue digits in the dominant hand during or after practice or competition using a 4-point Likert scale (never, sometimes, often and always). Kappa (κ) and percentage of agreement (POA) were calculated for individual symptoms, and to distinguish symptomatic and asymptomatic players. For the individual symptoms, κ ranged from “poor” (0.25) to “good” (0.63), and POA ranged from “moderate” (78%) to “good” (97%). To classify symptomatic players, the SPI-Q showed “good” reliability (κ = 0.83; 95%CI 0.69–0.97) and “good” agreement (POA = 92%). The current study has proven the SPI-Q to be reliable for detecting elite male indoor volleyball players with symptoms of digital ischemia.     

运动对骨骼肌、心肌中热休克蛋白表达影响的研究进展

热休克蛋白是一组结构高度保守的多肽,几乎所有生物体受到某种额外程度的应激时都有热休克蛋白的表达,因此又称为应激蛋白.热休克蛋白赋予细胞或生物体从各种应激中恢复的能力和保护他们免遭这些应激因素的伤害.其中,表现最为明显的是热耐受能力.热休克蛋白作为一种分子伴侣,能维持细胞的正常结构.热休克蛋白在抗氧化、抗细胞凋亡中也具有重要作用.运动也能诱导心肌、骨骼肌等组织中热休克蛋白的表达,并与运动方式、运动强度密切相关,在骨骼肌中的表达表现出肌纤维特异性.     

Match-derived relative pitch area changes the physical and team tactical performance of elite soccer players in small-sided soccer games

Small-sided games (SSGs) are used in training sessions to prepare for full-sized matches. For the same number of players, smaller pitch sizes result in decreased physical performance and shorter interpersonal distances. A relative pitch area derived from the full-sized match results in larger pitch sizes and this may increase the fit between SSGs and full-sized matches. This study aimed to investigate SSGs with a traditional small pitch and a match-derived relative pitch area in youth elite soccer players. Four age categories (under-13, under-15, under-17 and under-19) played 4 vs. 4 plus goalkeepers on a small (40x30m, 120m² relative pitch area) and large pitch (68x47m, 320m² relative pitch area). The number of games per age category ranged 15–30. Positional data (LPM-system) were collected to determine physical (total distance covered, high intensity distance and number of sprints) and team tactical (inter-team distance, LPW-ratio, surface area, stretch indices, goalkeeper-defender distance) performance measures and tactical variability. On a large pitch, physical performance significantly increased, inter-team and intra-team distances were significantly larger and tactical variability of intra-team distance measures significantly increased. The match-derived relative pitch area is an important training manipulation and leads to changes in physical and tactical performance 4 vs. 4 plus goalkeepers.     

Comparing the magnitude and direction of asymmetry during the squat,countermovement and drop jump tests in elite youth female soccer players

ABSTRACT

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists.