ISSN:0112-1642    

DOI:10.2165/00007256-198704030-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummarySoccer is a game that demands a combination of repeated maximal sprinting with 10 to 11km of moderate running, sometimes performed under extremely warm conditions. Over the course of a match, there is partial to near complete depletion of glycogen reserves in the leg muscles (depending on the extent of initial reserves and the level of competition), with a resultant decrease in physical performance. Blood glucose levels also fall, sometimes to values likely to cause a deterioration of both tactical thinking and cooperation between players (3.0 to 3.8 mmol/L), while in tropical climates, fluid losses can amount to 4 to 5 kg of body weight. The effectiveness of glucose solutions in correcting these problems is limited for 2 main reasons: concentrations greater than 2.5% slow the rate of gastric emptying and thus fluid absorption, while provoking a secretion of insulin with a resultant hypoglycaemia. Fructose solutions are less liable to increase insulin secretion, but they have an equal propensity for slowing gastric emptying; moreover, the ingested fructose is largely metabolised in the liver, without boosting blood glucose. However, glucose polymer preparations have a low osmotic pressure per unit content of glucose equivalent, so that substantial amounts of carbohydrate can be administered in this fashion before gastric emptying is inhibited. If polymers are given before and during a soccer game, they sustain blood glucose, sparing muscle glycogen stores and increasing game performance. If the concentration of polymer is too high, one possible complication is a movement of water from the plasma into the gut; nevertheless, with an appropriate choice of concentration (for example, 7% polycose, 360 mOsm/L, plasma volume is increased rather than decreased relative to that seen with administration of water. Probably because the intergame interval for competitive soccer players is short, replenishment of glycogen reserves proceeds quite slowly. Moreover, this process does not seem to be helped by ingestion of either glucose polymers or a high carbohydrate diet.

ISSN:0112-1642    

DOI:10.2165/00007256-198704030-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryCalcium antagonists lead to a relaxation of smooth vascular muscles and exert a cardiodepressive effect. They make up a heterogeneous group, with primarily substances of the nifedipine and verapamil type playing the most important role in the treatment of cardiocirculatory diseases. The principal indications include coronary heart disease and hypertension. During physical exercise, following the administration of calcium antagonists, V̇2maxand endurance performance are not impaired. The rate of perceived exertion does not increase to any greater extent in comparison with placebo. Nifedipine leads to an increase of noradrenaline (norepinephrine) as an expression of a reflex activation of the sympathetic system and to a slight increase in heart rate, while calcium antagonists of the verapamil type lower heart rate by 10 to 15 beats/min during physical exercise as a result of their intrinsic negative chronotropic effect. Cardiac output, in spite of the drop in heart rate, remains unchanged. Neither carbohydrate metabolism nor lipid metabolism, including lipolysis, which provide the essential energy-yielding substrates during exercise, are affected by calcium antagonists. Potassium likewise remains unchanged. The response of the hormones insulin, growth hormone and Cortisol is the same with calcium antagonists both during incremental graded exercise and during prolonged exercise as with placebo. In comparison with the administration of only calcium antagonists, the combination of calcium antagonists and β-blockers impairs physical performance. The diminishment in performance, however, is markedly less pronounced than with β-blocker monotherapy. Unimpaired performance is crucial for physically active patients. Especially for patients performing regular physical activity who suffer from mild hypertension, calcium antagonists provide a viable therapeutic alternative to β-blockers.

ISSN:0112-1642    

DOI:10.2165/00007256-198704030-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryBlunt trauma to the head results in acceleration of the brain within the skull. This takes 2 forms: linear or translational acceleration which produces focal lesions, and rotational acceleration which results in ‘sheering stresses’ with stretching of nerves and bridging veins. Deceleration of the brain within the skull occurs when the head strikes a stationary object (e.g. floor, ring post).Cerebrovascular events are not infrequently encountered. The most common vascular sequalae is the subdural haematoma, which is also the most frequent cause of death in boxers. Epidural bleeds are rare, and are generally due to deceleration of the brain. Subarachnoid bleeds have been rarely reported, but, like intraparenchymal haemorrhages, they do occur. Sudden flexion/extension of the neck is suggested as the mechanism of the occasional brainstem haemorrhage reported in boxing. Thrombosis of the internal carotid artery can occur secondary to direct blows to the neck or stretching of the contralateral carotid artery.The best known sequalae of boxing is traumatic encephalopathy — the ‘punch drunk’ syndrome. This is most common in second-rate and slugging type fighters. Severity correlates with the length of a boxer’s career and total number of bouts, with an incidence of approximately 18%. Three stages of clinical deterioration are seen, the encephalopathy may be progressive or may remain clinically stable at any level. The first stage consists of affective disturbances with psychiatric symptoms being most marked. During the second stage an accentuation of the psychiatric symptoms occurs and signs/symptoms of Parkinsonism develop. The final stage consists of a decrease in general cognitive function together with pyramidal tract disease. Generally 2 to 3 years elapse between the first and final stages. Neuropathological studies reveal abnormalities of the septum pellucidum, scarring of the cerebellar and cerebral cortices, and loss of pyramidal neurons in the substantia nigra with neurofibrillary tangles in the absence of senile plaques.A ‘groggy state’ can occur in some fighters with confusion, impaired active attention and alteration of consciousness. During this period the boxer is at greater risk to suffer brain injury as defensive reflexes are frequently lost. Other neurological syndromes have been reported in addition to the ‘groggy state’. These include a midbrain syndrome, headaches and cervical spinal injuries. Additionally, boxing appears to be a significant risk factor for the development of meningiomas.Radiological studies in boxers with pneumoencephalography (PEG) reveal cerebral/cerebellar atrophy, cavum septum pellucidum and dilation of the cisterna of lamina terminalis in a majority of boxers. These findings have been replicated with computerised tomography (CT) and appear to be more frequent in the boxers with the greater number of bouts. An association between abnormal CT scans and impairment in neuropsychological testing has been reported. Numerous studies using electroencephalography (EEG) have been reported in boxers, most showing abnormal findings on the EEG — generally slowing of the background rhythm into the theta range. A correlation between the number of bouts and their frequency and EEG abnormalities have been reported. While approximately 60% of boxers with encephalopathy show abnormal EEGs, the correlation is low. A smaller number of studies have failed to demonstrate EEG abnormalities. Currently it appears that EEG has a role in determining when a boxer will return to the ring, and is less of a diagnostic tool for evaluating the encephalopathy. Prospective studies are lacking.Other laboratory methods have been applied to study brain injury in boxers. Regional cerebral blood flow using xenon-133 inhalation has demonstrated a significant decrease in cerebral blood flow in professional boxers when compared to amateurs or controls. Elevation of brain creatine kinase, a cytoplasmic enzyme of the brain, correlates with the degree of cerebral trauma. Rises in the enzyme are seen in boxers, and appear to correlate with the number of blows suffered to the head.Two major avenues of change have been advanced to improve the safety of boxing. While studies are lacking, experience suggests that the use of protective headgear is not only ineffective, but may increase injuries, as previously glancing blows become more substantial. Conversely, while removing the head as a target would indeed decrease neurological sequalae, the practicality of this has been questioned. Further prospective studies are needed to answer many of the questions that have arisen.

ISSN:0112-1642    

DOI:10.2165/00007256-198704030-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummarySuccess in sports, as measured by competitive performance, is dependent upon a number of significant mental and physical components. Somatotype, motor skills, age, nutritional status, physiology, psychology, training level, genetic endowment, and injury risk are the major independent variables influencing performance. Unfortunately, the data available in this area of sports medicine are not always reliable or allow interstudy comparisons.This article reviews the historical and current information used to predict human performance in sports at the childhood and adolescent level. Although mesomorphy, and to a lesser extent ectomorphy, are positively associated with enhanced performance, successful athletes tend to have or acquire somatotypes characteristic of individuals already successful in a particular sport. For the most part, motor skills are age (chronological) and gender dependent. In general, the efficiency of movement progressively improves throughout childhood and into early adolescence and is highly dependent on environmental influences. A lower anaerobic and aerobic capacity reduces performance in the child and adolescent. Nonetheless, regular training can favourably improve motor skills and physiological fitness parameters. The relationship between endurance performance and aerobic capacity, however, is not strong at any age during childhood. Performance levels are reduced if nutrition is inadequate. A number of mental factors s uch as aggression, spirit, and self-confidence are also related to sports performance, although their correlation is unclear at present. Performance is influenced by the effect of genetic factors on specific traits in 30 to 85% of cases. Risk factors that negatively impact on performance levels include a history of previous injury, excessive training schedules, decreased fitness endurance, joint looseness or tightness, and certain personality traits.It is suggested that sport performance may be optimised by the early identification of individuals with positive genetic and somatotypic markers and negative risk factors. Motor skill development and physiological parameters can then be maximised by using regular, non-excessive training protocols, sound nutrition patterns, a safe environment and protective gear.Further investigations in this important area of sports medicine are essential in order to more fully characterise those criteria essential for successful sports participation. In particular, such studies should be purely longitudinal and should control for multiple confounding factors operating at different times.

ISSN:0112-1642    

DOI:10.2165/00007256-198704030-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198704030-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS