摘要:

SummaryRugby League is a game of physical contact that involves low-intensity, aerobic exercise, combined with periods of intermittent, intensive anaerobic exercise. Matches consist of two halves, each of 40 minutes, separated by a 10-minute recovery period, and are contested by 2 teams of 13 players (6 forwards and 7 backs).Whilst the amount of time spent by individual players on low-intensity exercise exceeds the duration of high-intensity exercise, the nature of the high-intensity efforts (involving sprinting, lower- and upper-body impacts and high force generation) is such that the overall intensity of the game is greatly increased. Individual players have been shown to cover distances of approximately 5000 to 8000m during a game, and be involved in 20 to 40 tackles. Maximum oxygen uptake (V̇O2max) values of around 56 ml/kg/min have been reported for rugby league players, with no differences between the values of forwards and backs.Forwards have, however, been shown to generally have higher body mass, subcutaneous fat and fat-free mass levels than backs. Backs have been found to be quicker than forwards and produce greater leg power output when related to fat-free mass. The amount of physiological data on rugby league players and the sport of rugby league is very limited, and there is considerable scope for future research in this area.

ISSN:0112-1642    

DOI:10.2165/00007256-199520030-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryBlisters occur frequently, especially in vigorously active populations. Studies using repetitive rubbing techniques show that blisters result from frictional forces that mechanically separate epidermal cells at the level of the stratum spinosum. Hydrostatic pressure causes the area of the separation to fill with a fluid that is similar in composition to plasma but has a lower protein level. About 6 hours after formation of the blister, cells in the blister base begin to take up amino acids and nucleosides; at 24 hours, there is high mitotic activity in the basal cells; at 48 and 120 hours, new stratum granulosum and stratum corneum, respectively, can be seen. The magnitude of frictional forces (Ff) and the number of times that an object cycles across the skin determine the probability of blister development — the higher the Ff, the fewer the cycles necessary to produce a blister. Moist skin increases Ff, but very dry or very wet skin decreases Ff. Blisters are more likely in skin areas that have a thick horny layer held tightly to underlying structures (e.g. palms of the hands or soles of the feet). More vigorous activity and the carrying of heavy loads during locomotion both appear to increase the likelihood of foot blisters.Antiperspirants with emollients and drying powders applied to the foot do not appear to decrease the probability of friction blisters. There is some evidence that foot blister incidence can be reduced by closed cell neoprene insoles. Wearing foot socks composed of acrylic results in fewer foot blisters in runners. A thin polyester sock, combined with a thick wool or polypropylene sock that maintains its bulk when exposed to sweat and compression, reduces blister incidence in Marine recruits. Recent exposure of the skin to repeated low intensity Ffresults in a number of adaptations including cellular proliferation and epidermal thickening, which may reduce the likelihood of blisters. More well-designed studies are necessary to determine which prevention strategies actually decrease blister probability.Clinical experience suggests draining intact blisters and maintaining the blister roof results in the least patient discomfort and may reduce the possibility of secondary infection. Treating deroofed blisters with hydrocolloid dressings provides pain relief and may allow patients to continue physical activity if necessary. There is no evidence that antibiotics influence blister healing. Clinical trials are needed to determine the efficacy of various blister treatment methods.Considering the pervasive nature of friction blisters, there is a substantial amount of basic and applied research that remains to be performed, especially in the areas of prevention and treatment.

ISSN:0112-1642    

DOI:10.2165/00007256-199520030-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryAcute mountain sickness (AMS) has long been recognised as a potentially life-threatening condition afflicting otherwise healthy normal individuals who ascend rapidly to high altitude where the partial pressure of oxygen (pO2) in the air is reduced. The symptoms of AMS (e.g. headache, poor appetite and nausea, fatigue and weakness, dizziness or light-headedness and poor sleep) are probably a consequence of disturbances in fluid balance brought about by severe tissue hypoxia. AMS can be prevented by an adequately slow ascent, which is the best method, but for those with limited time there are several drug therapies that provide a relatively good protection. Acetazolamide (250mg twice daily or 500mg slow release once daily), taken before and during, ascent is probably the treatment of choice; it improves gas exchange and exercise performance and reduces the symptoms of AMS in most individuals. Dexamethasone (4mg, 4 times daily) is more of value for short term treatment or prevention, and should never be used for more than 2 to 3 days. Prophylactic use of progesterone looks promising, but more studies are required.

ISSN:0112-1642    

DOI:10.2165/00007256-199520030-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryPhysical exercise influences the central dopaminergic, noradrenergic and serotonergic systems. A number of studies have examined brain noradrenaline (norepinephrine), serotonin (5-hydroxytryptamine; 5-HT) and dopamine with exercise. Although there are great discrepancies in experimental protocols, the results indicate that there is evidence in favour of changes in synthesis and metabolism of monoamines during exercise.There is a possibility that the interactions between brain neurotransmitters and their specific receptors could play a role in the onset of fatigue during prolonged exercise. The data on the effects of branched chain amino acid (BCAA) supplementation and ‘central fatigue’ seem to be conflicting, although recent studies suggest that BCAA supplementation has no influence on endurance performance.There are numerous levels at which central neurotransmitters can affect motor behaviour; from sensory perception, and sensory-motor integration, to motor effector mechanisms. However, the crucial point is whether or not the changes in neurotransmitter levels trigger or reflect changes in monoamine release. Until recently most studies were done on homogenised tissue, which gives no indication of the dynamic release of neurotransmitters in the extracellular space of living organisms.Recently, new techniques such as microdialysis and voltammetry were introduced to measurein vivorelease of neurotransmitters. Microdialysis can collect virtually any substance from the brain of a freely moving animal with a limited amount of tissue trauma. This method allows measurement of local neurotransmitter release during on-going behavioural changes such as exercise.The results of the first studies using these methods indicate that the release of most neurotransmitters is influenced by exercise. Although the few studies that have been published to date show some discrepancies, we feel that these recently developed and more sophisticatedin vivomethods will improve our insight into the relationship between the monoamine and other transmitters during exercise. Continued quantitative and qualitative research needs to be conducted so that a further understanding of the effects of exercise on brain neurotransmission can be gained.

ISSN:0112-1642    

DOI:10.2165/00007256-199520030-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryBoth hypo- and hyperthyroidism are characterised by exercise intolerance. In hypothyroidism, inadequate cardiovascular support appears to be the principal factor involved. Insufficient skeletal muscle blood flow compromises exercise capacity via reduced oxygen delivery, and endurance through decreased delivery of blood-borne substrates. The latter effect results in increased dependence on intramuscular glycogen. Additionally, decreased mobilisation of free fatty acids from adipose tissue and, consequently, lower plasma free fatty acid levels compound the problem of reduced lipid delivery to active skeletal muscle in the hypothyroid state. In contrast, cardiovascular support is enhanced in hyperthyroidism, implicating other factors in exercise intolerance. Greater reliance on muscle glycogen appears to be the primary reason for decreased endurance. Biochemical changes with hyperthyroidism that would favour enhanced flux through glycolysis may account for this dependence on glycogen. Deviations from normal thyroid function, and the ensuing exercise intolerance, require appropriate medical therapy to attain euthyroid status.

ISSN:0112-1642    

DOI:10.2165/00007256-199520030-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryRock climbing has become increasingly popular in the past decade. However, the increased participation exposes a greater number of climbers to potential injury. The risks involved with climbing increase in proportion to the skill-level of the climber: the higher the skill-level, the more hours are required for training and on more difficult routes.The hands are used as tools for the ascent, with much of the climber’s weight placed upon the fingers and also distributed through the wrist, elbow and shoulders. The combination of repetitive climbing and the excessive weight-bearing demands of the sport result in cumulative trauma to the upper limbs.Prevention should begin with educating climbers on the potential risk for injury. Although adequate rest between climbs and decreased training when pain is first encountered would aid in alleviating numerous problems, additional research directed towards improving training, treatment and rehabilitation programmes is warranted.

ISSN:0112-1642    

DOI:10.2165/00007256-199520030-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS