摘要:

Flexibility measures can be static [end of ROM (range of motion)], dynamicpassive (stiffness/compliance) or dynamic-active (muscle contracted, stiffness/compliance). Dynamic measures of flexibility are less dependent on patient discomfort and are more objective. Acute and chronic changes in flexibility are likely to occur with stretching exercises, but it is difficult to distinguish between changes in stretch tolerance as opposed to changes in muscle stiffness. How flexibility is measured impacts these findings. There is no scientifically based prescription for flexibility training and no conclusive statements can be made about the relationship of flexibility to athletic injury.The literature reports opposing findings from different samples, frequently does not distinguish between strain, sprain and overuse injury, and rarely uses the proper denominator of exposure. There is basic scientific evidence to suggest that active warm-up may be protective against muscle strain injury but clinical research is equivocal on this point. Typically, specific flexibility patterns are associated with specific sports and even positions within sports. The relationship of flexibility to athletic performance is likely to be sport-dependent. Decreased flexibility has been associated with increased in-line running and walking economy. Increased stiffness may be associated with increased isometric and concentric force generation, and muscle energy storage may be best manifested by closely matching muscle stiffness to the frequency of movement in stretch-shorten type contractions.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

Every year physicians all over the world are asked to perform preparticipation physical evaluations (PPE) for children involved in sports. The PPE should be brief yet comprehensive enough to determine which athletes are at risk. In addition, the examination may help determine the athlete's general health and maturity level, uncover any disqualifying conditions and may also help establish a doctorpatient relationship. PPEs should be performed 4 to 6 weeks prior to initiation of the sport and be repeated every 1 to 3 years. A station-based exam may help evaluate large numbers of athletes within a limited time period.The history is the most important aspect of the PPE and should focus on prior cardiovascular complications, a family history of cardiovascular death before 50 years of age and any other limiting medical problems. A general physical examination should be performed to focus on areas involved in sports participation. Laboratory tests are not usually necessary. Disqualifying conditions may be determined based on the physical abnormality present and the amount of contact or energy involved in the sport to be played.Throughout the world, sports participation is growing rapidly. Although these guidelines have been drafted by a consortium of sports-related and general practice groups in the US, they can easily be applied worldwide. Unfortunately the health of young adults in developing countries may not be as good as that of those residing in more industrialised countries, therefore each athlete must be considered individually. With this type of individualised approach the examining physician can make informed and intelligent decisions concerning the athlete's participation.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

For exercise modalities such as cycling which recruit a substantial muscle mass, muscle oxygen uptake (&OV0312;O2) is the primary determinant of pulmonary &OV0312;O2. Indeed, the kinetic complexities of pulmonary &OV0312;O2associated with exercise onset and the non-steady states of heavy (>lactate threshold) and severe [>asymptote of power-time relationship for high intensity exercise (&OV0312;)] exercise reproduce with close temporal and quantitative fidelity those occurring across the exercising muscles. For moderate (<lactate threshold) exercise and also rapidly incremental work tests, pulmonary (and muscle) &OV0312;O2increases as a linear function of work rate (≈9 to 11 ml O2/W/min) in accordance with theoretical determinations of muscle efficiency (≈30%). In contrast, for constant load exercise performed in the heavy and severe domains, a slow component of the &OV0312;O2response is manifest and pulmonary and muscle &OV0312;O2increase as a function of time as well as work rate beyond the initial transient associated with exercise onset.In these instances, muscle efficiency is reduced as the &OV0312;O2cost per unit of work becomes elevated, and in the severe domain, this &OV0312;O2slow component drives &OV0312;O2to its maximum and fatigue ensues rapidly. At pulmonary maximum oxygen uptake (&OV0312;O2max) during cycling, the maximal cardiac output places a low limiting ceiling on peak muscle blood flow, O2delivery and thus muscle &OV0312;O2. However, when the exercise is designed to recruit a smaller muscle mass (e.g. leg extensors, 2 to 3kg), mass-specific muscle blood flow and &OV0312;O2at maximal exercise are 2 to 3 times higher than during conventional cycling. Consequently, for any exercise which recruits more than ≈5 to 6kg of muscle at pulmonary &OV0312;O2max, there exists a mitochondrial or &OV0312;O2reserve capacity within the exercising muscles which cannot be accessed due to oxygen delivery limitations. The implications of these latter findings relate to the design of exercise tests. Specifically, if the purpose of exercise testing is to evaluate the oxidative capacity of a small muscle mass (<5 to 6kg), the testing procedure should be designed to restrict the exercise to those muscles so that a central (cardiac output, muscle O2delivery) limitation is not invoked. It must be appreciated that exercise which recruits a greater muscle mass will not stress the maximum mass-specific muscle blood flow and &OV0312;O2but rather the integration of central (cardiorespiratory) and peripheral (muscle O2diffusing capacity) limitations.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

Recent epidemiological studies indicate that individuals who maintain a physically active lifestyle are much less likely to develop impaired glucose tolerance and non—insulin-dependent diabetes mellitus (NIDDM). Moreover, it was found that the protective effect of physical activity was strongest for individuals at highest risk of developing NIDDM. Reducing the risk of insulin resistance and NIDDM by regularly performed exercise is also supported by several aging studies. It has been found that older individuals who vigorously train on a regular basis exhibit a greater glucose tolerance and a lower insulin response to a glucose challenge than sedentary individuals of similar age and weight.While the evidence is substantial that aerobic exercise training can reduce the risk of impaired glucose tolerance and NIDDM, the evidence that exercise training is beneficial in the treatment of NIDDM is not particularly strong. Many of the early studies investigating the effects of exercise training on NIDDM could not demonstrate improvements in fasting plasma glucose and insulin levels, or glucose tolerance. The adequacy of the training programmes in many of these studies, however, is questionable. More recent studies using prolonged, vigorous exercise-training protocols have produced more favourable results.There are several important adaptations to exercise training that may be beneficial in the prevention and treatment of insulin resistance, impaired glucose tolerance and NIDDM. An increase in abdominal fat accumulation and loss of muscle mass are highly associated with the development of insulin resistance. Exercise training results in preferential loss of fat from the central regions of the body and should therefore contribute significantly in preventing or alleviating insulin resistance due to its development. Likewise, exercise training can prevent muscle atrophy and stimulate muscle development. Several months of weight training has been found to significantly lower the insulin response to a glucose challenge without affecting glucose tolerance, and to increase the rate of glucose clearance during a euglycaemic clamp.Muscle glucose uptake is equal to the product of the arteriovenous glucose difference and the rate of glucose delivery or muscle blood flow. While it has been known for many years that insulin will accelerate blood glucose extraction by insulin-sensitive peripheral tissues, recent evidence suggests that it can also acutely vasodilate skeletal muscle and increase muscle blood flow in a dose-dependent manner. A reduced ability of insulin to stimulate muscle blood flow is a characteristic of insulin-resistant obese individuals and individuals with NIDDM. Exercise training, however, has been found to help alleviate this problem, and substantially improve the control of insulin over blood glucose.Improvements in insulin resistance and glucose tolerance with exercise training are highly related to an increased skeletal muscle insulin action. This increased insulin action is associated with an increase in the insulin-regulatable glucose transporters, GLUT4, and enzymes responsible for the phosphorylation, storage and oxidation of glucose. Changes in muscle morphology may also be important following training. With exercise training there is an increase in the conversion of fast twitch glycolytic IIb fibres to fast twitch oxidative IIa fibres, as well as an increase in capillary density. IIa fibres have a greater capillary density and are more insulin-sensitive and -responsive than IIb fibres. Evidence has been provided that morphological changes in muscle, particularly the capillary density of the muscle, are associated with changes in fasting insulin levels and glucose tolerance. Furthermore, significant correlations between glucose clearance, muscle capillary density and fibre type have been found in humans during a euglycaemic clamp.Exercise training may also improve control over hepatic glucose production by increasing the control of insulin over blood free fatty acid (FFA) levels. An elevation in FFA levels, which is associated with obesity and NIDDM, stimulates hepatic gluconeogenesis which in turn stimulates hepatic glucose production. An increase in blood FFA levels also inhibits skeletal muscle uptake and storage. Therefore, an increase in control over blood FFA levels would serve to increase peripheral glucose clearance as well as reduce hepatic glucose production.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

The aetiology of chronic functional lateral ankle instability is fairly well understood. Pathophysiological factors such as mechanical instability, proprioceptive deficit and peroneal muscle weakness have been demonstrated. Subtalar instability has been in focus during the last years as one of the possible factors behind chronic functional instability of the foot. The exact aetiology and the true incidence of subtalar ligament injuries remain unknown. Most subtalar ligamentous injuries probably occur in combination with injuries of the talo-tibial articulation. Subtalar instability can have the characteristics of chronic lateral instability or recurrent ankle sprains.Patients with chronic subtalar instability typically complain of ‘giving way’ symptoms and a history of recurrent sprains. Clinical examination including increased inwards rotation and forward displacement of the calcaneus may not be sufficient for the differentiation between ankle and subtalar instability. Radiographic imaging using stress radiographs may be necessary to assess subtalar instability. Subtalar instability can be defined as chronic functional instability with increased values of talar tilt and talo-calcaneal displacement as measured with standardised stress radiographs. Few authors have addressed the treatment of subtalar instability and the condition has not been clearly defined. Subtalar instability can be treated either with a tendon transfer or tenodesis procedure, such as the Chrisman-Snook or triligamentous tenodeses, or with an anatomic ligament reconstruction using the calcaneo-fibular, lateral talo-calcaneal and cervical ligaments combined with a reinforcement of the inferior extensor retinaculum. There have been no studies comparing anatomical and non-anatomical recon-structions and the long term results after ligamentous stabilisation are unknown.The focus of this article is on subtalar instability causing chronic functional ankle instability.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS

摘要:

Clinicians are faced with a growing number of athletes with injured tendons. Treatment of both acute and chronic injuries has proven to be quite complex. It is difficult to maintain the balance between resting the injured tendon and preventing atrophy of the surrounding muscles and joints. Questions also arise as to when the tendon should be strengthened and when the athlete is ready to return to full activity in sport. Through an awareness of the structural and mechanical properties of the tendon, an exercise programme for the rehabilitation of tendon injuries has been developed. It is recommended that this programme be used in combination with ice and other physical modalities. This approach will resolve most tendon injuries within 6 weeks of its implementation. The use of anti-inflammatory medications and surgery can only be recommended in select situations where more conservative measures are inadequate.

ISSN:0112-1642    

出版商:ADIS    

年代:1997

数据来源: ADIS