ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryWith the growing interest in exercise and sport and the significance of cardiovascular disease in the spinal cord injured population, the role of endurance training in improving cardiovascular health is of particular interest. Ordinary daily activities of those with spinal cord injury are usually not adequate to maintain cardiovascular fitness, and lack of participation in a regular activity programme may result in a debilitative cycle. As this occurs, there is a reduction in functional work capacity which may limit independence, and the reduction in cardiovascular fitness may increase the risk for cardiovascular disease. Work capacity in those with spinal cord injury is limited by loss of functional muscle mass and sympathetic control. Sympathetic nervous system impairment limits control of regional blood flow and cardiac output, and maximum heart rate following cervical lesions may be reduced to 110 to 130 beats/min. However, endurance training in quadriplegics and paraplegics can elicit improvements in exercise performance similar to those observed in able-bodied individuals. Review of 13 cardiorespiratory training studies involving spinal cord injured subjects revealed average improvements of 20% in V̇O2 maxand 40% in physical work capacity after 4 to 20 weeks of training. Based upon the positive results of these studies, the general endurance training guidelines for the normal population appear to also be appropriate for the spinal cord injured population. These guidelines can be followed during participation in a number of different activities and sports including wheelchair pushing, arm crank ergometry, aerobic swimming, ambulation training, canoeing and wheelchair basketball. There is no evidence that intense training and competition is harmful, but special areas of risk as a result of impairments in sensation, cardiovascular function, autonomic function and temperature regulation must be considered. The long term benefits of endurance training in those with spinal cord injury has not been adequately studied, but there is suggestion that similar physiological and psychological changes may occur as in able-bodied individuals.

ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe study of hormonal alterations due to exercise is of growing interest because of the implications for adaptation, performance, and health. The influence of the sympathoadrenal response on energy metabolism and fluid and electrolyte balance has been of primary interest in past research. Interpretation of results, however, is difficult because of the numerous factors which need to be controlled. Limitations in the interpretation of hormone levels exist because of changes in plasma volume and/or clearance rate and the influences of timing and method of blood sampling. Other factors which must be considered are the design of exercise protocols, and various subject characteristics (sex, age, fitness level, training history, diet, emotional status, diurnal and menstrual variations). Hormonal alterations during acute exercise occur primarily because of sympathoadrenal secretion of the catecholamines which initiate mobilisation of glucose and free fatty acids. This response, in turn, stimulates other endocrine glands and cells (anterior and posterior pituitary, adrenal cortex, thyroid, parathyroid, liver, pancreas, kidney) to secrete secondary hormones which potentiate fuel mobilisation and regulate water and electrolyte concentrations. As duration of exercise increases, nutrient and ion concentrations also influence hormonal responses. In recent years, research has focused on the effect of exercise-induced hormonal alterations on reproductive functioning and various endocrine-related diseases (hypopituitarism, diabetes, osteoporosis, cardiovascular disease). These topics, as well as a better understanding of mechanisms of action via receptor activity, influences on training adaptations, and implications (if any) of hormonal alterations for the growth and development of children, provide challenges for future research.

ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThis review has grouped many studies on different populations with different protocols to show the interactive effects of intensity, frequency and duration of training as well as the effects of initial fitness levels and programme length on cardiorespiratory fitness as reflected by aerobic power (V̇O2max). Within each level of exercise duration, frequency, programme length or initial fitness level, the greatest improvements in aerobic power occur when the greatest challenge to aerobic power occurs i.e., when intensity is from 90 to 100% of V̇O2max. The pattern of improvement where different intensities are compared with different durations suggests that when exercise exceeds 35 minutes, a lower intensity of training results in the same effect as those achieved at higher intensities for shorter durations. Frequencies of as low as 2 per week can result in improvements in less fit subjects but when aerobic power exceeds 50 ml/kg/min, exercise frequency of at least 3 times per week is required. As the levels of initial fitness improve, the change in aerobic power decreases regardless of the intensity, frequency or duration of exercise.Although these pooled data suggest that maximal gains in aerobic power are elicited with intensities between 90 to 100% V̇O2 max, 4 times per week with exercise durations of 35 to 45 minutes, it is important to note that lower intensities still produce effective changes and reduce the risks of injury in non-athletic groups.

ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryIt is commonly accepted that there are physiological and morphological gender differences. These differences become evident in the specific responses or magnitude of response to various training regimens. Very little difference is seen in the response to different modes of progressive resistance strength training. Men and women experience similar relative strength gains when training under the same programme. The evidence on body composition changes that occur with strength training is equivocal at this point. Researchers, however, suggest that there appears to be less muscle hypertrophy with strength improvement in women when compared to men.The data suggest that there are no differences between genders in central or peripheral cardiovascular adaptations to aerobic training. However, women in general have a reduced O2carrying capacity. Another factor that may be responsible for the sex differences seen in the metabolic responses to exercise may be the greater, essential sex specific fat of women. Sparling and Cureton (1983) have shown that differences in similarly trained male and female distance runners are due largly to percentage body fat, less to cardiorespiratory fitness and least to running economy. Pate et al. (1985) determined that men and women who are capable of similar performances, in this case a 15 mile race, do not differ in body composition, cardiorespiratory response or metabolic response. There appear to be no differences in relative increases in V̇O2 maxfor men and women when they are trained under the same intensity, frequency and duration. Mode of training also appears to elicit no sex difference. Hormonal factors lead to greater initial levels of high density lipoproteins in women. This appears to cause a smaller change in the total cholesterol-high density lipoprotein ratio than occurs with aerobic training in men. Generally, the menstrual cycle phase makes no difference to performance in women. The special cases of exercise in hot and cold environments persent conflicting evidence. When men and women are matched for surface area:mass, V̇O2 maxand percentage body fat, the major disadvantages women have in the heat disappear. The question of gender differences in the cold has yet to be fully explored. When the general population is compared, men appear to have an advantage over women.

ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryIntensive training for and competition in endurance events like the marathon are accompanied by injury to fibres in the active skeletal muscles. Evidence for the injury comes from the increases in intramuscular enzymes and myoglobin found in the blood following the exercise, from the subjective sensation of soreness in the muscles in the post-exercise period, and from direct histological examination of samples of the damaged muscles. Histological studies demonstrate that some muscle fibres undergo degenerative changes following the exercise; the necrosis is accomplished by macrophages and other phagocytic cells that invade the injured cells and the adjacent interstitium. Following the degeneration the fibres appear to be regenerated so that there is not a net loss of fibres. Precisely what initiates the cellular damage is not known, but hypotheses suggested include, ‘metabolic overload’ and ‘mechanical strain’. Eccentric contractions are known to cause the greater amount of damage in muscles, which suggests that high local tensions in fibres may be more important than metabolic considerations in the aetiology of the injury. Training reduces the magnitude of the damage that occurs in response to a given exercise task, although competitors in endurance events may demonstrate chronic muscle injury because of increasing training intensities. Other than training, there is no compelling evidence that any drug treatment or preventative measures will lessen this form of injury.

ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198603050-00007

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS