ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryHistorically, the bicycle has evolved through the stages of a machine for efficient human transportation, a toy for children, a finely-tuned racing machine, and a tool for physical fitness development, maintenance and testing. Recently, major strides have been made in the aerodynamic design of the bicycle. These innovations have resulted in new land speed records for human powered machines.Performance in cycling is affected by a variety of factors, including aerobic and anaerobic capacity, muscular strength and endurance, and body composition. Bicycle races range from a 200m sprint to approximately 5000km. This vast range of competitive racing requires special attention to the principle of specificity of training.The physiological demands of cycling have been examined through the use of bicycle ergometers, rollers, cycling trainers, treadmill cycling, high speed photography, computer graphics, strain gauges, electromyography, wind tunnels, muscle biopsy, and body composition analysis. These techniques have been useful in providing definitive data for the development of a work/performance profile of the cyclist.Research evidence strongly suggests that when measuring the cyclist’s aerobic or anaerobic capacity, a cycling protocol employing a high pedalling rpm should be used. The research bicycle should be modified to resemble a racing bicycle and the cyclist should wear cycling shoes. Prolonged cycling requires special nutritional considerations. Ingestion of carbohydrates, in solid form and carefully timed, influences performance. Caffeine appears to enhance lipid metabolism.Injuries, particularly knee problems which are prevalent among cyclists, may be avoided through the use of proper gearing and orthotics. Air pollution has been shown to impair physical performance. When pollution levels are high, training should be altered or curtailed.Effective training programmes simulate competitive conditions. Short and long interval training, blended with long distance tempo cycling, will exploit both the anaerobic and aerobic systems. Strength training, to be effective, must be performed with the specific muscle groups used in cycling, and at specific angles of involvement.

ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummarySynopsis:Clinicians should direct greater attention to positive health, with particular reference to the role of physical activity, in optimising the well-being of a child. Vigorous physical activity slows maturation, particularly if there is associated energy imbalance or emotional stress, but it does not greatly affect body size. Well-designed exercise programmes enhance the immediate physical, psychomotor and intellectual attainments of a child. Long term health benefits depend on a continuation of the physical activity. Internal motivation and the creation of positive attitudes are thus important. Acute illness is not prevented by vigorous exercise, but it has a favourable effect on the course of many chronic diseases. There are certain risks, including physical injury, psychological stress, and (occasionally) cardiac deaths, but in general, an exercise regimen enhances well-being, favouring the balanced development of a child.Concept of Health:Clinicians have traditionally viewed child health in terms of a steady weight gain and adherence to immunisation schedules. Interest in the broader World Health Organization definition of health was stimulated by the demonstration of poor physical performance in US children relative to their European counterparts, together with documentation of deteriorating oxygen transport in Canadian boys over the period from primary school to adolescence.Optimal Growth and Development:Comparisons with sedentary subjects have sometimes (but not always) shown that child athletes have slow growth, retardation of bone development, and (in girls) a delay of menarche. However, factors potentially confounding this comparison include the selection of athletes by body build, an inadequate energy intake in groups such as gymnasts, and the excitement of certain types of competition. A recent controlled study found some delay in wrist maturation, but no difference of overall size growth when selected classes at 2 primary schools were given an additional 5 hours of physical education per week.Well-being:There is lack of agreement on the extent to which the physical potential of a child can be enhanced by required programmes of physical activity. Negative results probably reflect inadequate training programmes, selection of initially fit subjects, or a masking of response by seasonal variations in physical condition. Gains of physical con-dition improve body image and thus the immediate well-being of a child. However, long term health benefits depend upon the faithful continuation of training sessions into adult life. There is no strong evidence that trainability is enhanced during adolesence, or that lack of training cannot be made good as an adult.

ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe best available assessment of aerobic capacity is measurement of the consumption of oxygen at maximal dynamic effort. When carefully administered, this measurement is remarkably reproducible. Major sources of error in obtaining this measurement include improper gas collection apparatus, inaccurate flow meters, and failure to correct for water pressure in the expired gas. Obtaining a truly maximal effort in an objective manner is also a major limitation. The protocol used in the measurement is of minor importance although treadmill testing usually gives higher values than stationary bicycling.The cost and inconvenience of direct methods of measurement have made indirect methods attractive; however, these methods give less accurate quantifications of aerobic capacity and are not as useful to the athlete interested in gauging his or her improvement following a chronic exercise programme.Extrapolating data obtained from the laboratory to performance in specific athletic endeavours is tenuous. Of course, elite marathon runners will have high maximal oxygen consumption. But one cannot accurately predict how individual athletes will perform in their events; these measurements do not account for the psychological component so important in athletic performance.Perhaps the best use of the measurement of maximal oxygen consumption in athletes is in assessing the success of training programmes in a longitudinal manner.

ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryPhysical training induces adaptive changes in skeletal muscle. These changes are localised to the active muscle with their magnitude depending upon the nature, i.e. time and intensity, of the training regimen. The most notable changes are increased concen-trations of mitochondria and glycogen.With endurance training there are major changes in metabolism in that there is a greater contribution of fat to the total metabolism during submaximal exercise. This re-sults in a conservation of the stores of glycogen with the net result of increasing total exercise capacity. This increased use of fat during submaximal exercise appears to be more closely related to the elevations in the concentration of mitochondria in muscle than to changes in total body maximal oxygen uptake. The combination of a greater contri-bution of fat to the metabolism and the elevated concentration of stored glycogen are prime factors contributing to the enhanced endurance capacity after endurance training.The mechanism for the greater use of fat after endurance training is discussed. Evi-dence now supports the hypothesis that this is due to a tighter control over the Embden-Meyerhof pathway as a result of the greater concentration of mitochondria. The effect of heavy resistance exercise on the size and strength of skeletal muscle is discussed. Some attention is focused on the recently revived controversy concerning whether muscle en-largement is the result of a hypertrophy of pre-existing fibres or of hyperplasia. It is con-cluded that although there is considerable evidence to support the development of hyper-trophy in response to heavy resistance exercise, the contention that a splitting of fibres occurs to produce a greater fibre number is presently poorly supported.

ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198401030-00007

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS