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1.
Abstract

In this study, we examined the effect of two creatine monohydrate supplementation regimes on 24-h urinary creatine and methylamine excretion. Nine male participants completed two trials, separated by 6 weeks. Participants ingested 4 × 5 g · day?1 creatine monohydrate for 5 days in one trial and 20 × 1 g · day?1 for 5 days in the other. We collected 24-h urine samples on 2 baseline days (days 1–2), during 5 days of supplementation (days 3–7), and for 2 days post-supplementation (days 8–9). Urine was assayed for creatine using high-performance liquid chromatography and methylamine using gas chromatography. Less creatine was excreted following the 20 × 1 g · day?1 regime (49.25 ± 10.53 g) than the 4 × 5 g · day?1 regime (62.32 ± 9.36 g) (mean ± s; P < 0.05). Mean total excretion of methylamine (n = 6) over days 3–7 was 8.61 ± 7.58 mg and 24.81 ± 25.76 mg on the 20 × 1 g · day?1 and 4 × 5 g · day?1 regimes, respectively (P < 0.05). The lower excretion of creatine using 20 × 1 g · day?1 doses suggests a greater retention in the body and most probably in the muscle. Lower and more frequent doses of creatine monohydrate appear to further attenuate formation of methylamine.  相似文献   

2.
The present study explored the method of testing muscle mechanical properties through the linear force–velocity (F–V) relationships obtained from loaded vertical jumps. Specifically, we hypothesised that the F–V relationship parameters depicting the force, power, and velocity of the tested muscles will differ among individuals of different physical fitness. Strength trained, physically active, and sedentary male participants (N = 10 + 10 + 10; age 20–29 years) were tested on maximum countermovement and squat jumps where manipulation of external loads provided a range of F and V data. The observed F–V relationships of the tested leg muscles were approximately linear and mainly strong (median correlation coefficients ranged from 0.77 to 0.92; all p < 0.05), independently of either the tested group or the jump type. The maximum power revealed higher values in the strength trained than in the physically active and sedentary participants. This difference originated from the differences in F-intercepts, rather than from the V-intercepts. We conclude that the observed parameters could be sensitive enough to detect the differences among both the individuals of different physical fitness and various jump types. The present findings support using loaded vertical jumps and, possibly, other maximum performance multi-joint movements for the assessment of mechanical properties of active muscles.  相似文献   

3.
Abstract

The aim of this study was to quantify the movement patterns of various playing positions during professional rugby union match-play, such that the relative importance of aerobic and anaerobic energy pathways to performance could be estimated. Video analysis was conducted of individual players (n=29) from the Otago Highlanders during six “Super 12” representative fixtures. Each movement was coded as one of six speeds of locomotion (standing still, walking, jogging, cruising, sprinting, and utility), three states of non-running intensive exertion (rucking/mauling, tackling, and scrummaging), and three discrete activities (kicking, jumping, passing). The results indicated significant demands on all energy systems in all playing positions, yet implied a greater reliance on anaerobic glycolytic metabolism in forwards, due primarily to their regular involvement in non-running intense activities such as rucking, mauling, scrummaging, and tackling. Positional group comparisons indicated that while the greatest differences existed between forwards and backs, each positional group had its own unique demands. Front row forwards were mostly involved in activities involving gaining/retaining possession, back row forwards tended to play more of a pseudo back-line role, performing less rucking/mauling than front row forwards, yet being more involved in aspects of broken play such as sprinting and tackling. While outside backs tended to specialize in the running aspects of play, inside backs tended to show greater involvement in confrontational aspects of play such as rucking/mauling and tackling. These results suggest that rugby training and fitness testing should be tailored specifically to positional groups rather than simply differentiating between forwards and backs.  相似文献   

4.
Abstract

Our aim was to present a mathematical model of rowing and sculling that allowed for a comparison of oar blade designs. The relative movement between the oar blades and water during the drive phase of the stroke was modelled, and the lift and drag forces generated by this complex interaction were determined. The model was driven by the oar shaft angular velocity about the oarlock in the horizontal plane, and was shown to be valid against measured on-water mean steady-state shell velocity for both a heavyweight men's eight and a lightweight men's single scull. Measured lift and drag force coefficients previously presented by the authors were used as inputs to the model, whichs allowed for the influence of oar blade design on rowing performance to be determined. The commonly used Big Blade, which is curved, and it's flat equivalent were compared, and blade curvature was shown to generate a 1.14% improvement in mean boat velocity, or a 17.1-m lead over 1500 m. With races being won and lost by much smaller margins than this, blade curvature would appear to play a significant role in propulsion.  相似文献   

5.
Health literacy represents an increasingly important subject in health sciences. This article initially illustrates a domain-specific model of physical activity-related health competence. Movement competence, control competence, and PA-specific self-regulation competence are described as sub-competencies.  相似文献   

6.
The following research approximated how the central nervous system of Paralympic wheelchair athletes resolve kinematic redundancies during upper-limb movements. A multibody biomechanical model of a tetraplegic Paralympic athlete was developed using subject-specific body segment parameters. The angular joint kinematics throughout a specified Paralympic sport movement (i.e., wheelchair curling) were experimentally measured using inertial measurement units. The motor control system of the Paralympian was mathematically modelled and simulated using forward dynamics optimization. The predicted kinematics from different optimization objective functions (i.e., minimizing resultant joint moments, mechanical joint power, and angular joint velocities and accelerations) were compared with those experimentally measured throughout the wheelchair curling movement. Of the optimization objective functions under consideration, minimizing angular joint accelerations produced the most accurate predictions of the kinematic trajectories (i.e., characterized with the lowest overall root mean square deviations) and the shortest optimization computation time. The implications of these control findings are discussed with regards to optimal wheelchair design through predictive dynamic simulations.  相似文献   

7.
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   

8.
The school subject Physical Education (PE) deals explicitly with the body and movement. Therefore, it is essential to define the content of PE based on these two aspects. Historically, school is mainly oriented towards the mind, which has recently been named competency. For that reason, the mind-body problem is omnipresent in PE. Additionally, the recent shift to developing competencies in PE is intensifying the dualism of mind and body by opposing knowledge and knowing-how. In a first step, this categorical difference between mind and body will be explained in the course of a philosophical discussion and illustrated with appropriate examples. As will be shown, the mind-body contrast should be considered as a continuum instead of a dualism. Therefore—in a second step—Green’s teaching continuum will give an answer to the question if the subject matter of PE is a combination of cognitive and motor activity or not. In a third step, Dewey’s concept of experience will be outlined, based on which the practice of doing sport is explained and developed. A fourth step will be to develop a complementary curricular model that attempts to connect the two poles “mind” and “body” by linking performance with content standards (forms of sport), based on the current discourse on competencies and standards. In this manner, the presentation of a curricular model for PE overcomes the Cartesian contrast between mind and body. Additionally, it gives an answer to the current discussion about competencies and standards in PE that emanates from other disciplines and should be self-confidently discussed in our own discipline.  相似文献   

9.
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   

10.
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11.
During the two world wars of the twentieth century, American cultural wares were spread far and wide, and the global pervasiveness of US troops contributed significantly toward this development. One major aspect of an American serviceman's spare time was his involvement with sporting pursuits and, where possible, baseball matches were played, and even formalized, in the guise of exhibition matches played for war charities. Little, if anything, has been written about the matches that were played by the American military outside the USA from the perspective of the indigenous population. This paper examines the English response to the ‘friendly’ American invasion: the invasion of allied troops and their favourite pastime, baseball. In doing so, it is evident that even though, on the whole, the troops were welcome, there was a less than positive reception for the American national game.  相似文献   

12.
The aim of this study was to investigate the reliability and validity of a soccer short passing test using the Footbonaut training system. Forty-eight young skilled soccer players and 31 lesser-skilled soccer players completed a test and a retest, each involving four sessions a day of a Footbonaut short passing test (FSPT). We found significant differences in mean execution times for skilled (mean [M]?=?2487, standard deviation [SD] ?=?155) and lesser-skilled players (M?=?2682, SD?=?176) but no significant difference in accuracy (M?=?74.13, SD?=?7.65; M?=?72.19, SD?=?8.13) between groups. The results from linear mixed-effects models show that there were no significant effects of repeated measurements on execution time. In contrast, we found an estimated increase of 0.86% in accuracy per session for both groups. In conclusion, the FSPT offers a reliable and valid method to differentiate young soccer players at different competitive levels, using execution time.  相似文献   

13.
Participation trends in 100 m (161 km) ultramarathon running competitions in North America were examined from race results from 1977 through 2008. A total of 32, 352 finishes accounted for by 9815 unique individuals were identified. The annual number of races and number of finishes increased exponentially over the study period. This growth in number of finishes occurred through a combination of (1) an increase in participation among runners ≥40 years of age from less than 40% of the finishes prior to the mid-1980s to 65–70% of the finishes since 1996, (2) a growth (p < 0.0001) in participation among women from virtually none in the late 1970s to nearly 20% since 2004, and (3) an increase in the average annual number of races completed by each individual to 1.3. While there has been considerable growth in participation, the 161 km ultramarathon continues to attract a relatively small number of participants compared with running races of shorter distances.  相似文献   

14.
There is currently a distinct dearth of research into how sports students' career aspirations are formed during their post-compulsory education. This article, based on an ethnographic study of sport students in tertiary education, draws on data collected from two first-year cohorts (n = 34) on two different courses at a further education college in England. The study draws on ethnographic observations, and semi-structured group interviews, to examine in-depth the contrasting occupational perspectives emergent within these two groups of mainly working-class students, and how specific cultural practices affect students' career aspirations. Utilising a Bourdieusian framework, the paper analyses the internalised, often latent cultural practices that impact upon these students' diverse career aspirations. The hitherto under-researched dimension of inter-habitus interaction and also the application of doxa are outlined. The article reveals how the two student cohorts are situated within a complex field of relations, where struggles for legitimisation, academic accomplishment and numerous forms of lucrative capital become habituated. The study offers salient Bourdieusian-inspired insights into the career aspirations of these predominantly working-class students and the ways in which certain educational practices contribute to the production and reproduction of class inequalities.  相似文献   

15.
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   

16.
The objective of the present study was to investigate the effects of combined training without caloric restriction on inflammatory markers in overweight girls. Thirty-three girls (13–17 years) were assigned into overweight training (n = 17) or overweight control (n = 16) groups. Additionally, a normal-weight group (n = 15) was used as control for the baseline values. The combined training programme consisted of six resistance exercises (three sets of 6–10 repetitions at 60–70% 1 RM) followed by 30 min of aerobic exercise (walking/running) at 50–80% VO2peak, performed in the same 60 min session, 3 days/weeks, for 12 weeks. Body composition, dietary intake, aerobic fitness (VO2peak), muscular strength (1 RM), glycaemia, insulinemia, lipid profile and inflammatory markers (C-reactive protein, interleukin-6, tumour necrosis factor-alpha, interleukin-10, leptin, resistin and adiponectin) were measured before and after intervention. There was a significant decrease in body fat (P < 0.01) and increase in fat-free mass (P < 0.01), VO2peak (P < 0.01), 1 RM for leg press (P < 0.01) and bench press (P < 0.01) in the overweight training group. Concomitantly, this group presented significant decreases in serum concentrations of C-reactive protein (P < 0.05) and leptin (P < 0.05), as well as in insulin resistance (P < 0.05) after the experimental period. In conclusion, 12 weeks of combined training without caloric restriction reduced inflammatory markers associated with obesity in overweight girls.  相似文献   

17.
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   

18.
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   

19.
Abstract

We analyse the evolution of the slope (critical speed) and the y-intercept (anaerobic distance capacity) of the linear distance–time relationship over a century of Olympic running performances. The distance–time relationship of each Olympic Games (1920–2004) was plotted using the performances in the 800-, 1500- and 5000-m track events. Values for critical speed and anaerobic distance capacity were determined by linear modelling. Mean performances for the 800, 1500 and 5000 m were 104.9 ± 1.5 s (1.4%), 217.2 ± 2.8 s (1.3%) and 808.9 ± 18.4 s (2.3%), respectively. Critical speed improved during the first three-quarters of the twentieth century to reach a plateau in 1984. This is in accordance with the literature (Peronnet & Thibault, 1989 Peronnet, F. and Thibault, G. 1989. Mathematical analysis of running performance and world running records. Journal of Applied Physiology, 67: 453–465. [PubMed], [Web of Science ®] , [Google Scholar]) and suggests that “human aerobic endurance” has improved within the century (+13.4%) and tends to stabilize. Anaerobic distance capacity was highly variable over the century (coefficient of variation = 9.4%) and did not show a linear improvement over the years as has previously been suggested (Peronnet & Thibault, 1989 Peronnet, F. and Thibault, G. 1989. Mathematical analysis of running performance and world running records. Journal of Applied Physiology, 67: 453–465. [PubMed], [Web of Science ®] , [Google Scholar]). This could be due to an artefact in the application of the two-parameter model to only three Olympic performances. A limitation to the use of this linear mathematical model to fit physiological data may have been demonstrated.  相似文献   

20.
This study examines the role of regional government quality in health-related participation in sport and physical activity among adults (18–64 years) in 28 European countries. The importance of the analysis rests in the relative autonomy that regional and local governments have over policy decisions connected with sport and physical activity. While existing studies have focussed on economic and infrastructural investment and expenditure, this research investigates the quality of regional governments across 208 regions within 28 European countries. The individual-level data stem from the 2013 Eurobarometer 80.2 (n?=?18,675) and were combined with regional-level data from Eurostat. An individual's level of participation in sport and physical activity was measured by three variables reflecting whether an individual's activity level is below, meets, or exceeds the recommendations of the World Health Organization. The results of multi-level analyses reveal that regional government quality has a significant and positive association with individual participation in sport and physical activity at a level meeting or exceeding the guidelines. The impact is much larger than that of regional gross domestic product per capita, indicating that regional disadvantage in terms of political quality is more relevant than being disadvantaged in terms of economic wealth.  相似文献   

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