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71.
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Context:
Although balance is generally recognized to be an important feature in ensuring good performance in soccer, its link with functional performance remains mostly unexplored, especially in young athletes.Objective:
To investigate changes in balance induced by fatigue for unipedal and bipedal static stances in young soccer players.Design:
Crossover study.Setting:
Biomechanics laboratory and outdoor soccer field.Patients or Other Participants:
Twenty-one male soccer players (age = 14.5 ± 0.2 years, height = 164.5 ± 5.6 cm, mass = 56.8 ± 6.8 kg).Intervention(s):
Static balance was assessed with postural-sway analysis in unipedal and bipedal upright stance before and after a fatigue protocol consisting of a repeated sprint ability (RSA) test (2 × 15-m shuttle sprint interspersed with 20 seconds of passive recovery, repeated 6 times).Main Outcome Measure(s):
On the basis of the center-of-pressure (COP) time series acquired during the experimental tests, we measured sway area, COP path length, and COP maximum displacement and velocity in the anteroposterior and mediolateral directions.Results:
Fatigue increased all sway values in bipedal stance and all values except COP velocity in the mediolateral direction in unipedal stance. Fatigue index (calculated on the basis of RSA performance) was positively correlated with fatigue/rest sway ratio for COP path length and COP velocity in the anteroposterior and mediolateral directions for nondominant single-legged stance.Conclusions:
Fatigued players exhibited reduced performance of the postural-control system. Participants with better performance in the RSA test appeared less affected by balance impairment, especially in single-legged stance.Key Words: postural sway, repeated sprint ability test, athletesKey Points
- In young soccer players, balance was adversely affected by fatigue.
- A moderate correlation existed between balance impairment and repeated sprint ability performance.
Balance and Fatigue
Both localized and whole-body fatigue cause degradation of postural-control performance, which is evident in the form of increased postural sway (ie, constant, slight corrective deviations from vertical when standing upright).11 This phenomenon, which has been extensively reported in the literature, is mainly due to changes in cardiac and respiratory contractions, fluid movement in the body, and release of metabolic products by muscle fibers and is caused by altered sensory information from the proprioceptive system.12 The magnitude of sway increase is partly influenced by exercise intensity and duration, but it also depends on the muscular groups involved.13 From this point of view, localized fatigue and whole-body fatigue are thought to trigger different disturbances of the postural-control system,14 although the net effect in terms of balance impairment may appear similar.Typical experiments aimed at assessing the effect of fatigue on static balance involve exercise such as the treadmill,15–17 cycle or rowing ergometer,14,15,18 isokinetic concentric actions, squat jumps, and heel raises.14,19 A few authors20,21 have evaluated the fatiguing effects of actual sport performance in triathletes22 and soccer players. In particular, Zemkova and Hamar20 and Brito et al21 analyzed center-of-pressure (COP) velocity of 19- to 21-year-old players (unipedal and bipedal stances with eyes open or closed) before a game, in the break period between the first and second halves, and after a game. When visual input was present, single-legged balance was reduced after the match. Less evident was the effect of fatigue on bipedal standing: changes were observed only when the support surface was unstable and visual input suppressed.The lack of experimental data regarding the effects of fatigue on balance in soccer players is somewhat surprising, considering that fatigue is implicated in injury occurrence23 and that a deficit in postural control may increase the risk of ankle injuries.24 Thus, it is reasonable to hypothesize that not only may fatigue associated with performance in a match impair balance (and thereby increase the risk of injuries) but also that superior physical fitness in better-trained athletes may limit this effect.Our goal was to assess postural-sway changes induced by fatigue subsequent to a controlled field test (repeated sprint ability [RSA]) representative of actual soccer activity in a cohort of young elite soccer players. We had 2 questions: (1) Is unipedal and bipedal static balance impaired by fatigue? (2) Is there a functional relationship between performance level in RSA and balance alterations? 相似文献73.
Claudia Baratto Sergio Caravita Giovanni B. Perego Gianfranco Parati 《Catheterization and cardiovascular interventions》2020,95(5):1059-1061
Stiff left atrial (LA) syndrome is a distinct phenotype of heart failure with preserved ejection fraction, characterized by predominant high LA pressure. We describe the case of a middle‐aged woman who developed exertional breathlessness during low‐dose radiotherapy for right breast cancer and who was eventually found to be affected by stiff LA syndrome. Invasive hemodynamics allowed the recognition of pathognomonic tall V waves in the wedge position during exercise, in spite of inconclusive noninvasive investigations. 相似文献
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Elisa Mazzoni Alfredo Corallini Alfonso Cristaudo Angelo Taronna Gianfranco Tassi Marco Manfrini Manola Comar Massimo Bovenzi Roberto Guaschino Francesca Vaniglia Corrado Magnani Ferruccio Casali Giovanni Rezza Giuseppe Barbanti-Brodano Fernanda Martini Mauro G. Tognon 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(44):18066-18071
Human malignant pleural mesothelioma (MPM) is considered a rare tumor, but recent estimations indicate that one-quarter million people will die of this neoplasm in Europe in the next three decades. The mineral asbestos is considered the main causative agent of this neoplasm. MPM is largely unresponsive to conventional chemotherapy/radiotherapy. In addition to asbestos exposure, genetic predisposition to asbestos carcinogenesis and to simian virus (SV)40 infection has also been suggested. SV40 is a DNA tumor virus found in some studies to be associated at high prevalence with MPM. SV40 sequences have also been detected, although at a lower prevalence than in MPM, in blood specimens from healthy donors. However, some studies have failed to reveal SV40 footprints in MPM and its association with this neoplasm. These conflicting results indicate the need for further investigations with new approaches. We report on the presence of antibodies in serum samples from patients affected by MPM that specifically react with two different SV40 mimotopes. The two SV40 peptides used in indirect ELISAs correspond to viral capsid proteins. ELISA with the two SV40 mimotopes gave overlapping results. Our data indicate that in serum samples from MPM-affected patients (n = 97), the prevalence of antibodies against SV40 viral capsid protein antigens is significantly higher (26%, P = 0.043) than in the control group (15%) represented by healthy subjects (n = 168) with the same median age (66 y) and sex. Our results suggest that SV40 is associated with a subset of MPM and circulates in humans. 相似文献
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INTRODUCTION: This paper, the eighth in the series, will address the ninth stage of a research project suggested in the first paper. The ten suggested stages are: 1. The initial idea (asking a research question). 2. Searching the literature. 3. Refining the research question. 4. Planning the study. 5. Writing a protocol. 6. Obtaining ethics approval and funding. 7. Piloting the project and project management. 8. Collecting data. 9. Analysing the data. 10. Writing up and disseminating the results. The previous paper outlined how to collect data during a research project. The next stage is to analyse the data that have been collected. This paper briefly introduces readers to data analysis and basic statistics. It updates the Faculty of General Dental Practice (UK) research advice sheets: Introduction to Statistics, Statistics for Research, Testing for Statistical Significance. 相似文献