摘要:

This part II discusses detraining following an insufficient training stimulus period longer than 4 weeks, as well as several strategies that may be useful to avoid its negative impact. The maximal oxygen uptake (V-dot2max) of athletes declines markedly but remains above control values during long term detraining, whereas recently acquired V-dot2maxgains are completely lost. This is partly due to reduced blood volume, cardiac dimensions and ventilatory efficiency, resulting in lower stroke volume and cardiac output, despite increased heart rates. Endurance performance is accordingly impaired. Resting muscle glycogen levels return to baseline, carbohydrate utilisation increases and the lactate threshold is lowered, although it remains above untrained values in the highly trained. At the muscle level, capillarisation, arterial-venous oxygen difference and oxidative enzyme activities decline in athletes and are completely reversed in recently trained individuals, contributing significantly to the long term loss in V-dot2max. Oxidative fibre proportion is decreased in endurance athletes, whereas it increases in strength athletes, whose fibre areas are significantly reduced. Force production declines slowly, and usually remains above control values for very long periods. All these negative effects can be avoided or limited by reduced training strategies, as long as training intensity is maintained and frequency reduced only moderately. On the other hand, training volume can be markedly reduced. Cross-training may also be effective in maintaining training-induced adaptations. Athletes should use similar-mode exercise, but moderately trained individuals could also benefit from dissimilar-mode cross-training. Finally, the existence of a cross-transfer effect between ipsilateral and contralateral limbs should be considered in order to limit detraining during periods of unilateral immobilisation.

ISSN:0112-1642    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

The consumption of oral creatine monohydrate has become increasingly common among professional and amateur athletes. Despite numerous publications on the ergogenic effects of this naturally occurring substance, there is little information on the possible adverse effects of this supplement. The objectives of this review are to identify the scientific facts and contrast them with reports in the news media, which have repeatedly emphasised the health risks of creatine supplementation and do not hesitate to draw broad conclusions from individual case reports.Exogenous creatine supplements are often consumed by athletes in amounts of up to 20 g/day for a few days, followed by 1 to 10 g/day for weeks, months and even years. Usually, consumers do not report any adverse effects, but body mass increases. There are few reports that creatine supplementation has protective effects in heart, muscle and neurological diseases. Gastrointestinal disturbances and muscle cramps have been reported occasionally in healthy individuals, but the effects are anecdotal. Liver and kidney dysfunction have also been suggested on the basis of small changes in markers of organ function and of occasional case reports, but well controlled studies on the adverse effects of exogenous creatine supplementation are almost nonexistent.We have investigated liver changes during medium term (4 weeks) creatine supplementation in young athletes. None showed any evidence of dysfunction on the basis of serum enzymes and urea production. Short term (5 days), medium term (9 weeks) and long term (up to 5 years) oral creatine supplementation has been studied in small cohorts of athletes whose kidney function was monitored by clearance methods and urine protein excretion rate. We did not find any adverse effects on renal function.The present review is not intended to reach conclusions on the effect of creatine supplementation on sport performance, but we believe that there is no evidence for deleterious effects in healthy individuals. Nevertheless, idiosyncratic effects may occur when large amounts of an exogenous substance containing an amino group are consumed, with the consequent increased load on the liver and kidneys. Regular monitoring is compulsory to avoid any abnormal reactions during oral creatine supplementation.

ISSN:0112-1642    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

During the past 2 decades, heart transplantation has evolved from an experimental procedure to an accepted life-extending therapy for patients with end-stage heart failure. However, with dramatic improvements in organ preservation, surgery and immunosuppressive drug management, short term survival is no longer the pivotal issue for most heart transplant recipients (HTR). Rather, a return to functional lifestyle with good quality of life is now the desired procedural outcome. To achieve this outcome, aggressive exercise rehabilitation is essential.HTR present unique exercise challenges. Preoperatively, most of these patients had chronic debilitating cardiac illness. Many HTR have had prolonged pretransplantation hospitalisation for inotropic support or a ventricular assist device. Decrements in peak oxygen consumption (V-dot2peak) and related cardiovascular parameters regress approximately 26% within the first 1 to 3 weeks of sustained bed rest. Consequently, extremely poor aerobic capacity and cardiac cachexia are not unusual occurrences in HTR who have required mechanical support or been confined to bed rest. Moreover, HTR must also contend withde novoexercise challenges conferred by chronic cardiac denervation and the multiple sequelae resulting from immunosuppression therapy.There is ample evidence that both endurance and resistance training are well tolerated in HTR. Moreover, there is growing clinical consensus that specific endurance and resistance training regimens in HTR can be efficacious adjunctive therapies in the prevention of immunosuppression-induced adverse effects and the reversal of pathophysiological consequences associated with cardiac denervation and antecedent heart failure. For example, some HTR who remain compliant during strenuous long term endurance training programmes achieve peak heart rate and V-dot2peakvalues late after transplantation that approach age-matched norms (up to approximately 95% of predicted). These benefits are not seen in HTR who do not participate in structured endurance exercise training. Rather, peak heart rate and V dotO2peakvalues in untrained HTR remain approximately 60 to 70% of predicted indefinitely. However, the mechanisms responsible for improved peak heart rate, V-dot2peakand total exercise time are not completely understood and require further investigation. Recent studies have also demonstrated that resistance exercise training may be an effective countermeasure for corticosteroid-induced osteoporosis and skeletal muscle myopathy. HTR who participate in specific resistance training programmes successfully restore bone mineral density (BMD) in both the axial and appendicular skeleton to pretransplantation levels, increase lean mass to levels greater than pretransplantation, and reduce body fat. In contrast, HTR who do not participate in resistance training lose approximately 15% BMD from the lumbar spine early in the postoperative period and experience further gradual reductions in BMD and muscle mass late after transplantation.

ISSN:0112-1642    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

Hypertension is a very prevalent cardiovascular (CV) disease risk factor in developed countries. All current treatment guidelines emphasise the role of nonpharmacological interventions, including physical activity, in the treatment of hypertension. Since our most recent review of the effects of exercise training on patients with hypertension, 15 studies have been published in the English literature. These results continue to indicate that exercise training decreases blood pressure (BP) in approximately 75% of individuals with hypertension, with systolic and diastolic BP reductions averaging approximately 11 and 8mm Hg, respectively. Women may reduce BP more with exercise training than men, and middle-aged people with hypertension may obtain greater benefits than young or older people. Low to moderate intensity training appears to be as, if not more, beneficial as higher intensity training for reducing BP in individuals with hypertension. BP reductions are rapidly evident although, at least for systolic BP, there is a tendency for greater reductions with more prolonged training. However, sustained BP reductions are evident during the 24 hours following a single bout of exercise in patients with hypertension.Asian and Pacific Island patients with hypertension reduce BP, especially systolic BP, more and more consistently than Caucasian patients. The minimal data also indicate that African-American patients reduce BP with exercise training. Some evidence indicates that common genetic variations may identify individuals with hypertension likely to reduce BP with exercise training. Patients with hypertension also improve plasma lipoprotein-lipid profiles and improve insulin sensitivity to the same degree as normotensive individuals with exercise training. Some evidence also indicates that exercise training in hypertensive patients may result in regression of pathological left ventricular hypertrophy. These results continue to support the recommendation that exercise training is an important initial or adjunctive step that is highly efficacious in the treatment of individuals with mild to moderate elevations in BP.

ISSN:0112-1642    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

Exercise prescription principles for persons without chronic disease and/or disability are based on well developed scientific information. While there are varied objectives for being physically active, including enhancing physical fitness, promoting health by reducing the risk for chronic disease and ensuring safety during exercise participation, the essence of the exercise prescription is based on individual interests, health needs and clinical status, and therefore the aforementioned goals do not always carry equal weight. In the same manner, the principles of exercise prescription for persons with chronic disease and/or disability should place more emphasis on the patient's clinical status and, as a result, the exercise mode, intensity, frequency and duration are usually modified according to their clinical condition. Presently, these exercise prescription principles have been scientifically defined for clients with coronary heart disease. However, other diseases and/or disabilities have been studied less (e.g. renal failure, cancer, chronic fatigue syndrome, cerebral palsy). This article reviews these issues with specific reference to persons with chronic diseases and disabilities.

ISSN:0112-1642    

出版商:ADIS    

年代:2000

数据来源: ADIS

摘要:

Exercise-related headache is one of the most common medical problems affecting the modern-day athlete. Despite the high prevalence of headache in community populations, the epidemiology of sports-related headache is unclear. In certain collision sports, up to 50% of athletes report regular headaches as a consequence of their athletic participation.The classification of the different types of sport-related headache by the International Headache Society (IHS) and in previously published articles does not adequately encompass the clinical problem faced by team physicians. Confusion exists where terms such as ‘effort headache’ and ‘exertional headache’ may be used to describe similar entities. In this review, the specific headache entities discussed include benign exertional headache, effort headache, acute post-traumatic headache and cervicogenic headache.For the sports physician, an understanding of the variety of specific headache syndromes that occur with particular sports is necessary for everyday clinical practice. This article reviews the common exercise-related headache syndromes and attempts to provide a framework for their overall management. Team physicians also need to be cognisant that many of the standard preparations used to treat headaches may be banned drugs under International Olympic Committee (IOC) rules.

ISSN:0112-1642    

出版商:ADIS    

年代:2000

数据来源: ADIS