ISSN:0112-1642    

DOI:10.2165/00007256-198704020-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198704020-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryIn general, the mobilisation of structural proteins is necessary for enzyme synthesis and for renewing cellular structures with amino acids and precursors of nucleone acids. However, during exercise the adaptive synthesis of proteins occurs only in the liver to some extent. In muscle tissue most protein synthesis is suppressed, although the synthesis of certain proteins in muscle remains unchanged or even increases. The general suppression of protein synthesis in muscle leaves much of the free amino acid pool unused. The break- down of tissue proteins may also increase in various tissues, but there is no convincing evidence for proteolysis of contractile proteins in active muscle.As a result of these processes, an increased pool of available free amino acids is created. The main use of free amino acids is connected with the energy requirement of muscular activity, through the oxidation of branched-chain amino acids and the use of alanine in gluconeogenesis. In active muscles the output of alanine is increased. It is based on usage of pyruvate, which is produced in increased amounts due to intensified glycogenosis and glycolysis, and of amino groups, which are liberated in oxidation of branched-chain amino acids. In the liver, alanine is consumed. The carbon skeleton of alanine is required for gluconeogenesis and the liberated amino groups are used in ureagenesis. The branched- chain amino acids are transported from the liver to active muscle for their oxidation. The increases in the free amino acid pool, in the rate of the glucose-alanine cycle, and in the use of amino acids in the liver are stimulated by an increased level of glucocorticoids and a decreased level of insulin during exercise.During recovery after exercise the use of amino acids for adaptive protein synthesis is intensified. This coincides with a persistently high rate of protein breakdown, constituting an increased rate of protein turnover. During recovery, the production of 3-methylhistidine by previously active muscles increases. It results in an increase in urinary output of 3- methylhistidine after exercise. Immediately after exercise the level of free 3-methylhistidine is elevated in the intestine for only a short time and the fact that it does not contribute significantly to the delayed increase in the excretion of 3-methylhistidine excretion after exercise must be considered as a sign of increased turnover of contractile proteins, helping to restore a good contractile function. Thus, the mobilisation of structural proteins gives an additional energy for contracting muscles during exercise and creates conditions for recovery and development of active cellular structures after exercise.

ISSN:0112-1642    

DOI:10.2165/00007256-198704020-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryGrowth hormone is a powerful anabolic hormone that affects all body systems and plays an important role in muscle growth. It is released from the anterior pituitary in response to a variety of stimuli including exercise, sleep, stress, and the administration of a variety of drugs and amino acids. Serum levels are variable and are dependent on such factors as age, sex, body composition and level of fitness. Animal experiments have shown that growth hormone can partially reverse surgically induced muscle atrophy and weakness. Growth hormone administration to normal animals leads to muscle hypertrophy, but this muscular growth is not accompanied by increased strength. Growth hormone excess leads to acromegaly, a disease with significant morbidity, including a myopathy in which muscles appear larger but are functionally weaker. Although there is no scientific evidence documenting an improvement in athletic performance following growth hormone supplementation, it is reported that this practice is becoming more widespread among athletes wishing to avoid detection with current doping control measures. There are anecdotal reports that athletes are injecting cadaveric or biosynthetic forms of growth hormone, both of which are associated with potentially serious complications. In addition, some athletes are ingesting drugs and amino acids in the belief that their endogenous growth hormone secretion will be increased. There have been no scientific studies on the effects of growth hormone supplementation, and the anecdotal reports have been equivocal, with some individuals reporting spectacular results while others report no change. Despite the lack of valid evidence for its efficacy and its potentially serious side effects, it has been predicted that growth hormone use may increase. Growth hormone use and abuse has the potential to dramatically change the future conduct of athletics and may prove to be a threat to the concept of fair competition.

ISSN:0112-1642    

DOI:10.2165/00007256-198704020-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryExercise testing can be performed safely in cystic fibrosis patients, and provides a simple and reproducible index of overall health in the disease. A wide variability in exercise capacity of cystic fibrosis patients is found, but, in general, exercise is limited by the degree of lung disease and, to a lesser extent, by compromised nutritional status. Based on the results of exercise tests, patients can then be supplied with individualised exercise prescriptions. Exercise training can be expected to improve the exercise capacity of the majority of cystic fibrosis patients, but pulmonary function generally remains unchanged. Whether exercise rehabilitation will improve the long term prognosis for patients with cystic fibrosis is currently not known.

ISSN:0112-1642    

DOI:10.2165/00007256-198704020-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198704020-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS