ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe rationale underlying the development of various formulations of beverages for consumption before, during, and/or after physical exercise is that such formulations should minimise some of the disturbances in physiological homeostasis that occur during exercise and thereby prevent injury and/or enhance performance. Exercise- and dehydration-induced increases in core temperature, body fluid osmolality, heart rate, losses of plasma and other body fluid volumes, and carbohydrate depletion are probably the most important homeostatic disturbances that can be ameliorated by fluid consumption. With the exception of athletes subject to hyponatraemia after consumption of ordinary water during prolonged activity, changes in electrolyte concentrations in the body fluids of most athletes do not justify the inclusion of electrolytes in fluid replacement beverages to be consumed during exercise. However, small amounts of sodium added to water does speed gastric emptying and fluid absorption from the intestine.Recent evidence suggests that a precompetition meal high in easily digested carbohydrates should be consumed not later than 5 to 6 hours before competition. There is little published research on the optimal composition of this meal. Water ingestion 30 to 60 minutes before exercise seems to be of benefit to temperature regulation and cardiovascular homeostasis if the exercise is of moderate intensity (50 to 65% V̇2max), but probably has little effect at the higher intensities of athletic performance. There is no systematic evidence to support the inclusion of calcium or sodium chloride in drinks consumed an hour or 2 before exercise. Furthermore, if glucose solutions are fed 15 to 45 minutes before prolonged exercise, they will probably cause a fall in blood glucose during exercise and may adversely affect performance. These adverse effects are not present when fructose is consumed before exercise. Contrary to the adverse effects of glucose feedings 15 to 60 minutes before exercise, the consumption of 18 to 50% solutions of glucose or glucose polymers 5 minutes before prolonged exercise seems to have potential for improving endurance performance. Similarly, the inclusion of caffeine in beverages consumed 60 minutes before prolonged exercise improves athletic performance for many subjects. Others may be hypersensitive to the effects of caffeine and are adversely affected by its use.For exercise leading to exhaustion in less than 30 minutes, neither caffeine nor carbohydrate ingestion is effective in minimising homeostatic perturbations or improving exercise performance. On the other hand, the addition of bicarbonate to precompetition drinks has been shown to favourably affect plasma pH and enhance exercise performance in events lasting from 1 to 10 minutes if the exercise test is preceded by a warmup exercise period lasting 10 to 30 minutes. Attempts to rehydrate with various beverages after self-imposed severe dehydration are often effective in restoring cardiovascular function to near normal levels, but they are almost always ineffective, regardless of beverage formulation, in restoring performance to the level achieved with normal hydration.Although much has been made of the critical importance of the gastric emptying rate for establishing the value of various beverage formulations for fluid replenishment during prolonged exercise, recent evidence suggests that differences in gastric emptying rates among beverages are not particularly important in determining the efficacy of various drinks for minimising homeostatic disturbances and enhancing performance. In spite of presumably slower rates of gastric emptying, beverages containing simple sugars or glucose polymers with or without small amounts of electrolytes minimise disturbances in temperature regulation and cardiovascular function as well as ordinary water, maintain blood glucose levels better than water, and are likely to enhance athletic performance compared with water. Therefore, although optimal formulations for prolonged exercise are still unknown, it seems appropriate to conclude that beverages containing 5 to 10% glucose or sucrose, or 5 to 20% glucose polymers in volumes of 150 to 250ml consumed every 15 to 20 minutes are preferable to ordinary water. The more palatable these beverages are for a given athlete, the more likely it is that enough liquid will be consumed during exercise to optimally affect homeostasis and performance.Little research has been published on the question of optimal beverage formulations for rehydration during recovery periods following exercise. From what is known, it appears that fluids containing glucose, sucrose, or glucose polymers in concentrations of 5 to 20% might be appropriate if rapid rehydration is a reasonable objective. To quickly restore electrolytes lost during exercise, small amounts of sodium, chloride, and potassium may be added to the recovery beverages; if speed of recovery is not critical, the normal athlete’s diet can usually meet the electrolyte replacement needs.

ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe metabolic and hormonal adaptations to single exercise sessions and to exercise training in normal man and in patients with insulin-dependent as well as non-insulin-dependent diabetes mellitus are reviewed.In insulin-dependent (type I) diabetes good metabolic control is best obtained by a regular pattern of life which will lead to a fairly constant demand for insulin from day to day. Exercise is by nature a perturbation that makes treatment of diabetes difficult: Muscle contractions per se tend to decrease the plasma glucose concentration whereas the exercise-induced response of the so-called counter-regulatory hormones tend to increase plasma glucose by increasing hepatic glucose production and adipose tissue lipolysis. If the pre-exercise plasma insulin level is high, hypoglycaemia may develop during exercise whereas hyperglycaemia and ketosis may develop if pre-exercise plasma insulin levels are low. Physical activity is often difficult to carry out on a precise schedule and the exercise-induced changes in demand for insulin and calories vary according to the intensity and duration of exercise, time of day, and differ within and between individuals. Thus, physical training can not be recommended as a means of improving metabolic control in insulin-dependent diabetes. However, our present knowledge and technology allows the well-informed and cooperative patient to exercise and even to reach the elite level. To achieve this, pre-exercise metabolic control should be optimal and knowledge of the patient’s reaction to exercise is desirable, which necessitates frequent self-monitoring of plasma glucose. It may often be necessary to diminish the insulin dose before exercise, and/or to ingest additional carbohydrate during or after exercise.In non-insulin-dependent (type II) diabetes, exercise is associated with less risk of metabolic derangement, and in genetically disposed individuals physical training may prevent development of overt diabetes possibly by diminishing the strain on the pancreatic beta cell. The latter, however, is only achieved if exercise is not accompanied by increased caloric intake.Whether physical training in diabetes can reduce cardiovascular morbidity and mortality is at present unknown, but training has in diabetic patients been shown to lessen some risk factors for development of arteriosclerosis. However, training of diabetics (especially in the less well-regulated patient) may not lessen coronary risk factors to the same extent as in healthy subjects.

ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryJumper’s knee is a typical functional overload injury because it affects those athletes who submit their knee extensor mechanisms to intense and repeated stress, e.g. volleyball and basketball players, high and long jumpers. According to the classification of Perugia and colleagues, it is an insertional tendinopathy affecting, in order of frequency, the insertion of the patellar tendon into the patella (65% of cases), attachment of the quadriceps tendon to the patella (25%) and the attachment of the patellar tendon to the tibial tuberosity (10%). The frequent occurrence of this injury in athletes led to the study of factors that may contribute to its onset and aggravation. These factors are divided into extrinsic (i.e. kind of sport practised and training methods used) and intrinsic (i.e. connected with the somatic and morphological characteristics of the athletes).On the basis of our experience and after a review of the literature it appears, contrary to what has been repeatedly claimed in the past, the extrinsic factors are more important than the intrinsic in the aetiology of jumper’s knee. The effect of traumatic incidents and use of elastic kneecap guards should also be considered negligible.The intrinsic causes of jumper’s knee, can be sought in the mechanical properties of tendons (resistance, elasticity and extensibility) rather than in morphological or biomechanical abnormalities of the knee extensor mechanism.

ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryViruses are ubiquitous and cause numerous infections in humans. These may vary from asymptomatic infection to severe debilitating illness. Viruses enter the host cells to replicate, using host synthetic mechanisms, and, thus, are resistant to conventional antibiotics. The human body responds to viral infection by synthesising specific antibody which can be used to aid diagnosis. Infectious mononucleosis (glandular fever) commonly affects the 15 to 30 years age group. It may produce severe debility which may last a month or more. Coxsackie virus infection can produce symptoms of the common cold but may also invade heart muscle and produce myocarditis, a potentially serious disease. Other viruses also produce a wide spectrum of disease.Recent evidence has shown that people undergoing severe mental or physical stress may have reduced immunity to viral infections. There are risks associated with strenuous physical activity during the acute phase of viral infection, and there are reports of sudden death and serious complications occurring in previously fit young adults who undertake vigorous exercise when in the acute phase of a viral illness. Abnormalities of skeletal muscle have been demonstrated in patients with viral infection and this may explain the loss of performance experienced by athletes after upper respiratory tract infection.As a general rule, for all but mild common colds, it is advised that the athlete avoids hard training for the first month after infection.

ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198603040-00007

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS