摘要:

It is estimated that most individuals are not ingesting sufficient amounts of chromium in their diets. Although there is little information on chromium intake in athletes, many athletes ingest more calories than do non-athletes so their chromium intake should be adequate. However, athletes who restrict calories to maintain low bodyweights could compromise their chromium status. Some evidence also shows that exercise may increase chromium loss into the urine. At present, it is not known whether this loss necessitates additional chromium in the diet or whether the body will increase retention in response to the loss. Chromium deficiency is thought to contribute to glucose intolerance and unhealthy blood lipid profiles. The primary function of chromium is to potentiate the effects of insulin, and thereby alter glucose, amino acid and fat metabolism. Chromium supplements have been purported to increase muscle mass and decrease body fat. However, the preponderance of evidence has not supported this claim. There is little information available on the long term use of chromium supplements, but at present, supplements within the Estimated Safe and Adequate Daily Dietary Allowance (ESADDI) level do not appear harmful. The prudent course of action for athletes would be to ingest foods rich in chromium and perhaps take a multivitamin/mineral supplement containing no more than the ESADDI of chromium.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

The sport scientist's understanding of the biomechanics and physiology of sailing, together with its application to nutrition, training and injury prevention in the elite competitor, has continued to develop over the past decade. Very large mechanical forces are imposed in the vertical axis of the body, which give rise to frequent complaints of low back and knee pain and, occasionally, even to muscle rupture. Training programmes should emphasise the development of isometric endurance in the relevant muscle groups, such preparation continuing throughout the winter months. The oxygen cost of sailing is relatively light, and development of aerobic fitness should be advocated for reasons of general health rather than competitive success. Because of the intense muscle contractions that are developed during competition, heart rates and blood pressures are high in relation to oxygen consumption. However, during normal sailing, tacking and fluctuations of wind speed limit the development of muscle fatigue. In contrast to the operation of small craft, the crew of large ocean-going vessels may have a very high daily energy expenditure, probably related to difficulty in relaxing at any point of day or night. Windsurfers face similar physiological demands to the dinghy sailor and they also have frequent complaints of back pain. Knowledge of the relevant health issues remains limited, even among elite competitors, and there remains substantial scope for increased education of team members.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

Investigations on reproductive function in male athletes are not as abundant in the literature as the research available on female athletes. The primary reason for this is the absence of an obvious clinical sign indicative of an alteration in reproductive function in male athletes. While alterations in the reproductive status of female athletes may be easily detected by the loss of menstrual regularity, a distinctive clinical sign reflective of reproductive dysfunction in the male is not apparent.In male runners, an effect of endurance training on reproductive function related to a specific ‘volume threshold’ of training is proposed. Data are supportive of this ‘volume threshold’ effect, provided careful and consistent definitions of volume of training are applied. In fact, if volume of training is carefully defined endurance-trained male runners exhibit a rather consistent range of subclinical modifications in the gonadal hormones and semen profile, and clinical (oligospermia) alterations in reproductive function. The precise mechanism responsible for these observed alterations remains unknown, although several peripheral and central mechanisms have been suggested. Clearly, more research is necessary to confirm, and to elucidate, the nature of the ‘volume threshold’ hypothesis in male runners.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

Rugby union enjoys worldwide popularity, but there is a lack of comprehensive research into the anthropometric and physiological characteristics of its players and the demands of the game, particularly at the elite level. One of the possible explanations for this is that the sport has previously been primarily concerned with the aspects of skill related to the game, rather than the physical and physiological requirements.However, with the increased physiological demands being placed on the elite players (using the British Isles as an example), with the recent introduction of professionalism, regional championships, the World Cup and major tours, information about the demands of the game and the assessment of, and methods of improving, the anthropometric and physiological characteristics of its players, are of paramount importance.Match analysis has indicated that rugby is an interval or intermittent sport and players must be able to perform a large number of intensive efforts of 5 to 15 seconds' duration with less than 40 seconds' recovery between each bout of high intensity activity. These observations, together with the metabolic responses during the game, give some insight into its physiological demands and are a prerequisite in the development and prescription of training programmes by coaches in preparing individual players for competition.The results from studies reporting the anthropometric and physiological characteristics of rugby union players observed that these individuals had unique anthropometric and physiological attributes which depended on positional role and the playing standard. These have important implications for team selection and highlight the necessity for individualised training programmes and fitness attainment targets.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

Pre-exercise stretching and adequate warm-up are important in the prevention of hamstring injuries. A previous mild injury or fatigue may increase the risk of injury.Hamstring muscle tear is typically partial and takes place during eccentric exercise when the muscle develops tension while lengthening, but variation in injury mechanisms is possible. Diagnosis of typical hamstring muscle injury is usually based on typical injury mechanism and clinical findings of local pain and loss of function. Diagnosis of avulsion in the ischial tuberosity, with the need for longer immobilisation, and a complete rupture of the hamstring origin, in which immediate operative treatment is necessary, poses a challenge to the treating physician. X-rays, ultrasonography or magnetic resonance imaging (MRI) may be helpful in differential diagnostics.After first aid with rest, compression, cold and elevation, the treatment of hamstring muscle injury must be tailored to the grade of injury. Conservative treatment is based on a knowledge of the biological background of the healing process of the muscle. Experimental studies have shown that a short period of immobilisation is needed to accelerate formation of the granulation tissue matrix following injury. The length of the immobilisation is, however, dependent on the grade of injury and should be optimised so that the scar can bear the pulling forces operating on it without re-rupture. Mobilisation, on the other hand, is required in order to regain the original strength of the muscle and to achieve good final results in resorption of the connective tissue scar and re-capillarisation of the damaged area. Another important aim of mobilisation - especially in sports medical practice - is to avoid muscle atrophy and loss of strength and extensibility, which rapidly result from prolonged immobilisation.Complete ruptures with loss of function should be operated on, as should cases resistant to conservative therapy in which, in the late phase of repair, the scar and adhesions prevent the normal function of the hamstring muscle.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS