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1.
The purpose of this study was to examine the effects of varying amounts of dynamic stretching (DS) on joint range of motion (ROM) and stiffness of the muscle–tendon unit (MTU). Fifteen healthy participants participated in four randomly ordered experimental trials, which involved one (DS1), four (DS4) and seven (DS7) sets of DS, or control conditions/seated at rest (CON). Each DS set consisted of 15 repetitions of an ankle dorsiflexion–plantarflexion movement. The displacement of the muscle–tendon junction (MTJ) was measured using ultrasonography while the ankle was passively dorsiflexed at 0.0174 rad · s?1 to its maximal dorsiflexion angle. Passive torque was also measured using an isokinetic dynamometer. Ankle ROM was significantly increased after DS4 and DS7 compared with the pre-intervention values (P < 0.05), but there were no significant differences in ankle ROM between DS4 and DS7. No differences were observed in ankle ROM after DS1 and CON. In addition, the stiffness of the MTU, passive torque and displacement of the MTJ at submaximal dorsiflexion angles did not change in any of the experimental conditions. These results indicate that DS4 increased ankle ROM without changing the mechanical properties of the MTU, and that this increase in ankle ROM plateaued after DS4.  相似文献   

2.
Abstract

There has been no previous investigation of the concurrent validity and reliability of the current 5 Hz global positioning system (GPS) to assess sprinting speed or the reliability of integrated GPS–accelerometer technology. In the present study, we wished to determine: (1) the concurrent validity and reliability of a GPS and timing gates to measure sprinting speed or distance, and (2) the reliability of proper accelerations recorded via GPS–accelerometer integration. Nineteen elite youth rugby league players performed two over-ground sprints and were simultaneously assessed using GPS and timing gates. The GPS measurements systematically underestimated both distance and timing gate speed. The GPS measurements were reliable for all variables of distance and speed (coefficient of variation [CV] = 1.62% to 2.3%), particularly peak speed (95% limits of agreement [LOA] = 0.00 ± 0.8 km · h?1; CV = 0.78%). Timing gates were more reliable (CV = 1% to 1.54%) than equivalent GPS measurements. Accelerometer measurements were least reliable (CV = 4.69% to 5.16%), particularly for the frequency of proper accelerations (95% LOA = 1.00 ± 5.43; CV = 14.12%). Timing gates and GPS were found to reliably assess speed and distance, although the validity of the GPS remains questionable. The error found in accelerometer measurements indicates the limits of this device for detecting changes in performance.  相似文献   

3.
The aim of the present study was to examine the effects of viscoelastic properties of human tendon structures during stretch?–?shortening cycle exercise. The elongation of tendon and aponeurosis of the medial gastrocnemius muscle of 26 participants was measured by ultrasonography while they performed ramp isometric plantar flexion up to the voluntary maximum, followed by a ramp relaxation. The relationship between estimated muscle force and tendon elongation during the ascending phase was fitted to a linear regression, the slope of which was defined as stiffness. The percentage of the area within the muscle force?–?tendon elongation loop relative to the area beneath the curve during the ascending phase was defined as hysteresis. In addition, maximal voluntary concentric contractions at 2.09 and 3.14 rad?·?s?1 with and without prior eccentric contractions were performed. The difference in the concentric torque at equivalent joint angles with and without prior eccentric contractions (i.e. pre-stretch augmentation) was negatively correlated with stiffness (P <?0.05) and hysteresis (P <?0.05). Furthermore, there was a higher correlation between the pre-stretch augmentation and the viscoelastic properties index – that is, the sum of normalized score values of stiffness and hysteresis (P <?0.01) – than with either stiffness or hysteresis alone. The results of this study suggest that performance during stretch?–?shortening cycle exercise is significantly affected by the viscoelastic properties of the tendon structures.  相似文献   

4.
Abstract

Individuals have to reweight the respective contribution of the different sources of sensorial information for regulating posture and balance, especially during fine task execution. Given the evidences indicating strategy during swing performance as associated with prioritization of task-relevant visuospatial information for skill execution, the aim of the present work is to assess differences in visual dependency (VD) and postural control in a population of expert (EXP) and non-expert (NEXP) golfers when compared with healthy subjects (HC) and to discover possible relationships between these outcomes and swing performance. Thus, 15 golfers (EXP?=?7; NEXP?=?8) and 32 matched HC underwent otoneurological testing including video Head Impulse Test, posturography and Rod and Disk Test (RDT). Golf players also underwent a swing session procedure, which performance was measured by means of the Flightscope X2 Doppler-radar launch monitor system. EXP subjects demonstrated significant (p?<?0.05) lower values in i) counter-clockwise (CCW) and clockwise (CW) dynamic conditions when compared with both NEXP and HC subjects RDT outcome measures and ii) surface and length posturography values as compared with HC subjects. When treating golf players outcomes as ‘a continuum’, CCW and CW scores were found to positively correlate with both lateral distance and horizontal launch angle and to negatively correlate with spin rpm. In conclusion, the present study suggests that the high-level of visual-independency demonstrated by EXP subjects may be functionally related in expert golfers to an effective motor strategy preferentially not referring to an inappropriate reliance on visual input.  相似文献   

5.
Carbohydrate ingestion can improve endurance exercise performance. In the past two decades, research has repeatedly reported the performance benefits of formulations comprising both glucose and fructose (GLUFRU) over those based on glucose (GLU). This has been usually related to additive effects of these two monosaccharides on the gastrointestinal tract whereby intestinal carbohydrate absorption is enhanced and discomfort limited. This is only a partial explanation, since glucose and fructose are also metabolized through different pathways after being absorbed from the gut. In contrast to glucose that is readily used by every body cell type, fructose is specifically targeted to the liver where it is mainly converted into glucose and lactate. The ingestion of GLUFRU may thereby profoundly alter hepatic function ultimately raising both glucose and lactate fluxes. During exercise, this particular profile of circulating carbohydrate may induce a spectrum of effects on muscle metabolism possibly resulting in an improved performance. Compared to GLU alone, GLUFRU ingestion could also induce several non-metabolic effects which are so far largely unexplored. Through its metabolite lactate, fructose may act on central fatigue and/or alter metabolic regulation. Future research could further define the effects of GLUFRU over other exercise modalities and different athletic populations, using several of the hypotheses discussed in this review.  相似文献   

6.
Abstract

The aims of this study were to examine training characteristics, body composition, muscular strength, and endurance in sport climbers, and to demonstrate the relationship among these components by means of structural equation modelling. Altogether, 205 sport climbers (136 males, 69 females), with a performance RP (red point) of grade 4 to 11 on the Union Internationale des Association d'Alpinisme (UIAA) scale, took part in the study. The proposed structural model, with latent variable hand–arm strength and endurance (developed from reference values for simple tests), indicated by three manifest variables (grip strength, bent-arm hang, and finger hang) and three exogenous variables (body fat, volume of climbing, and climbing experience), explained 97% of the variance in climbing performance. The relationship between body fat and climbing experience/volume with climbing performance was not direct, but was better explained using the mediator hand–arm strength and endurance. We conclude that these simple tests, together with percent body fat, volume of climbing, and climbing experience, can satisfactorily predict climbing performance.  相似文献   

7.
《Sport in Society》2012,15(1):88-102
This study examines whether a process of internationalization has affected the level of athletic performance amongst high-level athletes competing on the world stage. Top 100 International Association of Athletics Federations (IAAF) rankings were compared at two time points: 1984 and 2006, by event and by gender. We identified internationalization as a determinant of the level of athletic performances. This level increased more in events that witnessed more important shifts in market shares (dynamic internationalization or competitiveness) and where dominance by a subset of countries (static internationalization) decreased. This internationalization clearly affects performances in men's athletics (as the performance has clearly gone up since 1984), but not in women's athletics. Here the general level of women's athletics has actually decreased.  相似文献   

8.
Abstract

Recent international normative data for the 20-m shuttle-run test demonstrated a below-average performance index for UK children. The aims of the present study were to create an international comparison of 20-m shuttle-run test performance in a sample of English children and to identify age- and sex-specific differences in test performance. Mass, stature, body mass index, and 20-m shuttle-run test performance were measured in 2041 children aged 11 – 15 years (963 boys, 1078 girls). Performance was expressed as maximum running velocity and a performance index was created by generating z-scores. The shuttle-run test performance index was higher than the existing published value (?0.046, 95% confidence interval [CI] ?0.070 to ?0.022) for all children (0.061, 95% CI = 0.006 to 0.115), for boys (0.075, 95% CI = ?0.022 to 0.171), and for girls (0.048, 95% CI = ?0.010 to 0.106). Boys' relative performance increased significantly (F = 4.43, P = 0.002) throughout the measured age range, whereas girls' relative performance tended to decrease (F = 1.98, P = 0.096). The results were favourable when compared with existing values. Differences in performance index may be due to the different geographical areas from which present and past samples were drawn. Reasons for differences in the performance indices between boys and girls warrant further investigation.  相似文献   

9.
This study examined the effects of different work?–?rest durations during 40?min intermittent treadmill exercise and subsequent running performance. Eight males (mean?±?s: age 24.3?±?2.0 years, body mass 79.4?±?7.0?kg, height 1.77?±?0.05?m) undertook intermittent exercise involving repeated sprints at 120% of the speed at which maximal oxygen uptake (v-[Vdot]O2max) was attained with passive recovery between each one. The work?–?rest ratio was constant at 1:1.5 with trials involving short (6:9?s), medium (12:18?s) or long (24:36?s) work?–?rest durations. Each trial was followed by a performance run to volitional exhaustion at 150% v-[Vdot]O2max. After 40?min, mean exercise intensity was greater during the long (68.4?±?9.3%) than the short work?–?rest trial (54.9?±?8.1% [Vdot]O2max; P?<?0.05). Blood lactate concentration at 10?min was higher in the long and medium than in the short work?–?rest trial (6.1?±?0.8, 5.2?±?0.9, 4.5?±?1.3?mmol?·?l?1, respectively; P?<?0.05). The respiratory exchange ratio was consistently higher during the long than during the medium and short work?–?rest trials (P <?0.05). Plasma glucose concentration was higher in the long and medium than in the short work?–?rest trial after 40?min of exercise (5.6?±?0.1, 6.6?±?0.2 and 5.3?±?0.5?mmol?·?l?1, respectively; P?<?0.05). No differences were observed between trials for performance time (72.7?±?14.9, 63.2?±?13.2, 57.6?±?13.5?s for the short, medium and long work?–?rest trial, respectively; P = 0.17), although a relationship between performance time and 40?min plasma glucose was observed (P?<?0.05). The results show that 40?min of intermittent exercise involving long and medium work?–?rest durations elicits greater physiological strain and carbohydrate utilization than the same amount of intermittent exercise undertaken with a short work?–?rest duration.  相似文献   

10.
Abstract

The aims of the present study were to assess the maximal oxygen uptake and body composition of adult Chinese men and women, and to determine how these variables relate to age. The cross-sectional sample consisted of 196 men and 221 women aged 20 – 64 years. Maximal oxygen uptake ([Vdot]O2max) was determined by indirect calorimetry during a maximal exercise test on an electrically braked cycle ergometer. The correlations between [Vdot]O2max and fat mass were ?0.52 in men and ?0.58 in women. Linear regression defined the cross-sectional age-related decline in [Vdot]O2max as 0.35 ml · kg?1 · min?1 · year?1 in men and 0.30 ml · kg?1 · min?1 · year?1 in women. Multiple regression analysis showed that more than 50% of this cross-sectional decline in [Vdot]O2max was due to fat mass, lean mass, and age. Adding fat mass and lean mass to the multiple regression models reduced the age regression mass from 0.35 to 0.24 ml · kg?1 · min?1 · year?1 in men and from 0.30 to 0.15 ml · kg?1 · min?1 · year?1 in women. We conclude that age, fat mass, and lean mass are independent determinants of maximal oxygen uptake in Chinese adults.  相似文献   

11.
Despite the ongoing globalization of football culture and societies at large, there remain important cross-national and cross-local variations in the level and forms of football hooliganism. These dissimilarities thwart efforts to conceptualize and explain football hooliganism as a homogeneous phenomenon and, more specifically, seriously limit the applicability of dominant sociological theories on the subject. The author illustrates his argument with an examination of international research literature and empirical data on the social composition of one Spanish and one Dutch hooligan group. He argues that comparative research into football hooliganism should move beyond general explanations in terms of societal fault lines and towards a more detailed analysis of hooligans' subcultural identities and social interactions.  相似文献   

12.
Abstract

We sought to examine whether the relationship between recovery–stress factors and performance would differ at the beginning (Stage 1) and the end (Final Stage) of a multi-stage cycling competition. Sixty-seven cyclists with a mean age of 21.90 years (SD?=?1.60) and extensive international experience participated in the study. The cyclists responded to the Recovery–Stress Questionnaire for Athletes (RESTQ-Sport) and rated their performance (1?=?extremely poor to 10?=?excellent) in respect to the first and last stage. Two step-down multiple regression models were used to estimate the relationship among recovery (nine factors; e.g. Physical Recovery, Sleep Quality) and stress factors (10 factors; e.g. Lack of Energy, Physical Complaints), as assessed by the RESTQ-Sport and in relation to performance. Model 1 pertained to Stage 1, whereas Model 2 used data from the Final Stage. The final Model 1 revealed that Physical Recovery (β?=?.46, p?=?.01), Injury (β?=??.31, p?=?.01) and General Well-being (β?=??.26, p?=?.04) predicted performance in Stage 1 (R2?=?.21). The final Model 2 revealed a different relationship between recovery–stress factors and performance. Specifically, being a climber (β?=?.28, p?=?.01), Conflicts/Pressure (β?=?.33, p?=?.01), and Lack of Energy (β?=??.37, p?=?.01) were associated with performance at the Final Stage (R2?=?.19). Collectively, these results suggest that the relationship among recovery and stress factors changes greatly over a relatively short period of time, and dynamically influences performance in multi-stage competitions.  相似文献   

13.
Abstract

We tested some of the key predictions of processing efficiency theory using a simulated rally driving task. Two groups of participants were classified as either dispositionally high or low anxious based on trait anxiety scores and trained on a simulated driving task. Participants then raced individually on two similar courses under counterbalanced experimental conditions designed to manipulate the level of anxiety experienced. The effort exerted on the driving tasks was assessed though self-report (RSME), psychophysiological measures (pupil dilation) and visual gaze data. Efficiency was measured in terms of efficiency of visual processing (search rate) and driving control (variability of wheel and accelerator pedal) indices. Driving performance was measured as the time taken to complete the course. As predicted, increased anxiety had a negative effect on processing efficiency as indexed by the self-report, pupillary response and variability of gaze data. Predicted differences due to dispositional levels of anxiety were also found in the driving control and effort data. Although both groups of drivers performed worse under the threatening condition, the performance of the high trait anxious individuals was affected to a greater extent by the anxiety manipulation than the performance of the low trait anxious drivers. The findings suggest that processing efficiency theory holds promise as a theoretical framework for examining the relationship between anxiety and performance in sport.  相似文献   

14.
The aim of the study was to compare the effects of different strength training intensities on climbing performance, climbing-specific tests and a general strength test. Thirty lower grade and intermediate-level climbers participated in a 10-week training programme. The participants were randomized into three groups: high resistance–few repetitions training groups (HR-FR), low resistance–high repetitions training groups (LR-HR) and a control group (CON) which continued climbing/training as usual. Post-testing results demonstrated statistical tendencies for climbing performance improvements in the HR-FR and LR-HR (p?=?0.088–0.090, effect size?=?0.55–0.73), but no differences were observed between the groups (p?=?0.950). For the climbing-specific tests, no differences were observed between the groups (p?=?0.507–1.000), but the HR-FR and LR-HR improved their time in both Dead-hang (p?=?0.004–0.026) and Bent-arm hang (p?<?0.001–0.002). The HR-FR and LR-HR improved their 12RM strength in pull-down (p?≤?0.001), but not the CON group (p?=?0.250). No differences were observed in the CON group in any of the tests (p?=?0.190–0.596) with the exception of improvement in Bent-arm Hang (p?=?0.018). The training groups reduced their climbing sessions during the intervention compared to the CON group (p?=?0.057–0.074). In conclusion, HR-FR and LR-HR training programmes demonstrated an 11% and 12% non-significant improvement in climbing performance despite a 50% reduction in climbing sessions, but improved the results in strength and climbing-specific tests. None of the training intensities was superior compared to the others.  相似文献   

15.
A popular algorithm to predict VO2Peak from the one-mile run/walk test (1MRW) includes body mass index (BMI), which manifests practical issues in school settings. The purpose of this study was to develop an aerobic capacity model from 1MRW in adolescents independent of BMI. Cardiorespiratory endurance data were collected on 90 adolescents aged 13–16 years. The 1MRW was administered on an outside track and a laboratory VO2Peak test was conducted using a maximal treadmill protocol. Multiple linear regression was employed to develop the prediction model. Results yielded the following algorithm: VO2Peak = 7.34 × (1MRW speed in m s?1) + 0.23 × (age × sex) + 17.75. The New Model displayed a multiple correlation and prediction error of R = 0.81, standard error of the estimate = 4.78 ml kg?1·min?1, with measured VO2Peak and good criterion-referenced (CR) agreement into FITNESSGRAM’s Healthy Fitness Zone (Kappa = 0.62; percentage agreement = 84.4%; Φ = 0.62). The New Model was validated using k-fold cross-validation and showed homoscedastic residuals across the range of predicted scores. The omission of BMI did not compromise accuracy of the model. In conclusion, the New Model displayed good predictive accuracy and good CR agreement with measured VO2Peak in adolescents aged 13–16 years.  相似文献   

16.
This paper compares French- and English-language Canadian television coverage of Australian Aboriginal athlete Cathy Freeman during the 2000 Olympics using a narrative framework. The specific focus of the analysis is the representation of Freeman's political identity as an agent and symbol of Aboriginal reconciliation – the struggle for apology, reparatio, and social justice in the light of the history and legacy of colonial oppression and exclusion. Freeman has used her sporting success to signify visibly and with some controversy her identification with political Aboriginality and reconciliation, and she went into the 2000 games bearing an unusual weight of expectation, intensified by being chosen to light the Olympic cauldron, that a victory in the 400 metres would mark symbolically reconciliation between Aboriginal and non-Aboriginal Australians. The analysis generally conforms the hypothesis that the normative dimension of these expectations would be accentuated more in the French- than English-language coverage, and this resulted in a more consistently affirmative portrayal of Freeman and her performance. The English-language coverage emphasized the ambivalent nature of her role. The corollary of this was that the English-language coverage paid greater attention to the substance of Aboriginal grievances and struggle. Nonetheless, neither network saw Freeman's identity in openly critical terms: in Freeman's Olympic narrative sport and politics were allowed to mix in a relatively unproblematic way.  相似文献   

17.
Abstract

There is little published data in relation to the effects of caffeine upon cycling performance, speed and power in trained cyclists, especially during cycling of ~60 s duration. To address this, eight trained cyclists performed a 1 km time-trial on an electronically braked cycle ergometer under three conditions: after ingestion of 5 mg · kg?1 caffeine, after ingestion of a placebo, or a control condition. The three time-trials were performed in a randomized order and performance time, mean speed, mean power and peak power were determined. Caffeine ingestion resulted in improved performance time (caffeine vs. placebo vs. control: 71.1 ± 2.0 vs. 73.4 ± 2.3 vs. 73.3 ± 2.7 s; P = 0.02; mean ± s). This change represented a 3.1% (95% confidence interval: 0.7–5.6) improvement compared with the placebo condition. Mean speed was also higher in the caffeine than placebo and control conditions (caffeine vs. placebo vs. control: 50.7 ± 1.4 vs. 49.1 ± 1.5 vs. 49.2 ± 1.7 km · h?1; P = 0.0005). Mean power increased after caffeine ingestion (caffeine vs. placebo vs. control: 523 ± 43 vs. 505 ± 46 vs. 504 ± 38 W; P = 0.007). Peak power also increased from 864 ± 107 W (placebo) and 830 ± 87 W (control) to 940 ± 83 W after caffeine ingestion (P = 0.027). These results provide support for previous research that found improved performance after caffeine ingestion during short-duration high-intensity exercise. The magnitude of the improvements observed in our study could be due to our use of sport-specific ergometry, a tablet form and trained participants.  相似文献   

18.
Abstract

The aims of this study were to examine the acute effects of static stretching on peak torque, work, the joint angle at peak torque, acceleration time, isokinetic range of motion, mechanomyographic amplitude, and electromyographic amplitude of the rectus femoris during maximal concentric isokinetic leg extensions at 1.04 and 5.23 rad · s?1 in men and women. Ten women (mean ± s: age 23.0 ± 2.9 years, stature 1.61 ± 0.12 m, mass 63.3 ± 9.9 kg) and eight men (age 21.4 ± 3.0 years, stature 1.83 ± 0.11 m, mass 83.1 ± 15.2 kg) performed maximal voluntary concentric isokinetic leg extensions at 1.04 and 5.23 rad · s?1. Following the initial isokinetic tests, the dominant leg extensors were stretched using four static stretching exercises. After the stretching, the isokinetic tests were repeated. Peak torque, acceleration time, and electromyographic amplitude decreased (P≤ 0.05) from pre- to post-stretching at 1.04 and 5.23 rad · s?1; there were no changes (P > 0.05) in work, joint angle at peak torque, isokinetic range of motion, or mechanomyographic amplitude. These findings indicate no stretching-related changes in the area under the angle – torque curve (work), but a significant decrease in peak torque, which suggests that static stretching may cause a “flattening” of the angle – torque curve that reduces peak strength but allows for greater force production at other joint angles. These findings, in conjunction with the increased limb acceleration rates (decreased acceleration time) observed in the present study, provide tentative support for the hypothesis that static stretching alters the angle – torque relationship and/or sarcomere shortening velocity.  相似文献   

19.
This article examines theories and practices of moral and physical education among the Scottish missionaries in the Malawi region of south-central Africa during late nineteenth and early twentieth centuries. Within the wider history of British imperial education and the English public school games ethic, the Scottish missionaries of the Livingstonia and Blantyre missions offer an interesting and important counterpoint to their middle-class English counterparts. Although the Scots had their own distinct educational traditions which shaped their pedagogical programmes in Africa, they were not unaffected by the games ethic. Drill and team games gradually became an important part of missionary education in Blantyre and Livingstonia, with the holistic aim of developing the body, mind and moral character of the mission pupils. In Malawi, the games ethic, first introduced by middle-class Edinburgh missionaries, developed alongside an ‘industrial ethic’, and a distinctly ‘Scottish blend’ of missionary education that combined Scottish industrial and English non-industrial traditions emerged.  相似文献   

20.
Set against the background of France's cultural history during the Second World War, this biographical study concerns Alfred Nakache, a swimming champion of Jewish origin. Through his conditions of existence, the study amply demonstrates the exclusion, followed by the extermination, of Jews in France. At a time when the ‘Révolution Nationale’ (National Revolution) had been established as political dogma, it also demonstrates the bipolarity of the swimmer's identity, as both an emblem standing for the ‘New Man’ in the eyes of the ‘Commissariat Général à l'Education Générale et aux Sports (CGEGS)’ (commission for general education and sport) and a member of an inferior race for the Nazi occupiers and the ‘Commissariat Général aux Questions Juives (CGQJ)’ (administrative body concerned with French policy towards Jews). Although temporarily protected by his rank as an athlete and his network of contacts, the hardening of German policies, together with widespread collaboration during 1943, led the leading actors of the sport world to curtail his sport achievements, thus marking the beginning of progressive anonymization which, in turn, finally ended in his deportation in January 1944.  相似文献   

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