ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryA review of the English language literature establishes athletic mishaps as a major cause of posterior cruciate ligament injury. However, diversity of opinion exists regarding the functional significance of the lesion, its occurrence as an isolated entity, and the roles of conservative and surgical management.The posterior cruciate ligament is a composite structure, consisting of a superficial tibiofemoral and meniscofemoral portion and a deep tibiofemoral portion. The structure is intra-articular but extrasynovial, coursing from its attachment to the lateral surface of the medial femoral condyle posteriorly and inferiorly to its distal attachment into the posterior rim of the tibia, blending with the capsule and periosteum. Mechanical studies have demonstrated that abnormal posterior tibial displacement can occur only with posterior cruciate ligament laxity.The most prevalent mechanism resulting in injury to the posterior cruciate results from a blow on the anterior aspect of the flexed knee. However, both hyperflexion and hyperextension as well as deceleration and rotation have been described.Posterior cruciate ligament insufficiency may result from an avulsion fracture involving the ligament-bone insertion of the ligament, usually from the posterior aspect of the proximal tibia. Also, disruption may occur as an intersubstance tear of the ligament, either as an isolated phenomenon or in combination with multiple ligamentous injuries. The importance of distinguishing between combined injuries associated with significant collateral and/or anterior cruciate ligament injuries from the ‘isolated’ type lies in the fact that the prognosis for the ‘isolated’ injuries is much better.Careful clinical evaluation of the knee with an acute posterior cruciate ligament injury will reveal subtle, but definite, findings peculiar to the lesion. These include the posterior sag sign, the posterior drawer sign, reverse pivot shift, Godfrey’s test, and the presence of varus or valgus instability with the joint in full extension. In patients with chronic posterior cruciate ligament laxity, the presenting symptom is often that of patellar pain. It is generally agreed that avulsion fractures involving the ligament-bone insertion of the posterior cruciate ligament should be treated by open reduction and internal fixation. Surgical treatment of this lesion will result in excellent functional recovery.A variety of procedures have been reported for the management of acute disruption of the posterior cruciate ligament. Although most authors recommend a surgical approach to this problem, isolated lesions without associated internal derangement can be successfully managed conservatively. However, when operation is elected, the procedure of choice (as described by Clancy) appears to be primary repair with augmentation consisting of a free graft of a bone-patellar tendon-bone preparation.When chronic posterior cruciate ligament insufficiency does not respond to a vigorous rehabilitation programme, surgical reconstruction may be entertained. Again, a variety of procedures have been reported, with autogenous graft replacement using a bone-patellar tendon-bone preparation being the procedure of choice.

ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe study of fluctuations in athletic performance attributable to the menstrual cycle has been an area of considerable interest and controversy for well over half a century. Studies have included simple observations of performance in athletic events, and have also documented specific physical psychological and physiological changes as they relate to varying hormonal levels of the menstrual cycle.Advantages and disadvantages to human performance have been attributed to various phases of the cycle. Many investigators have documented evidence to suggest that the premenstrual phase is often associated with decreased performance. Others have noted that there are specific physiological changes, inherent in athletic performance, occurring in the follicular and luteal phases of the menstrual cycle. However, it is evident that there is conflict within the literature.This review considers the evidence for the cyclic effects of the regular or normal menstrual cycle on performance. It examines surveyed evidence of the effects of the regular menstrual cycle on athletic performance, effects on psychological and perceptual factors, maximum oxygen uptake, endurance and time to fatigue, temperature, sweating, body-weight, respiratory drive, blood lactate, carbohydrate and lipid metabolism, and cardiovascular parameters.It is concluded that there is considerable variation in the findings of the literature and that any reported variations in performance may well be greatly influenced by intersubject variability, the nature of the exercise, and the nutritional status of the athlete, as well as minor changes that could be attributable to the menstrual cycle.

ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryProlonged exercise in the fasted state frequently results in a lowering of blood glucose concentration, and when the intensity is moderate (i.e. 60–80% of V̇O2max), muscle often becomes depleted of glycogen. The extent to which carbohydrate feedings contribute to energy production, and their effectiveness for improving endurance during prolonged exercise, are reviewed in this article.Prolonged exercise (i.e.>2 hours) results in a failure of hepatic glucose output to keep pace with muscle glucose uptake. As a result, blood glucose concentration frequently declines below 2.5 mmol/L. Despite this hypoglycaemia, fewer than 25% of subjects display symptoms suggestive of central nervous system dysfunction. Since fatigue rarely results from hypoglycaemia alone, the effectiveness of carbohydrate feeding should be judged by its potential for muscle glycogen sparing.Carbohydrate feeding during moderate intensity exercise postpones the development of fatigue by approximately 15 to 30 minutes, yet it does not prevent fatigue. This observation agrees with data suggesting that carbohydrate supplementation reduces muscle glycogen depletion. It is not certain whether carbohydrate feeding increases muscle glucose uptake throughout moderate exercise or if glucose uptake is higher only during the latter stages of exercise.In contrast to moderate intensity exercise, carbohydrate feeding during low intensity exercise (i.e.<45% of V̇O2max) results in hyperinsulinaemia. Consequently, muscle glucose uptake and total carbohydrate oxidation are increased by approximately the same amount. The amount of ingested glucose which is oxidised is greater than the increase in total carbohydrate oxidation and therefore endogenous carbohydrate is spared. The majority of sparing appears to occur in the liver, which is reasonable since muscle glycogen is not utilised to a large extent during mild exercise.Although carbohydrate feedings prevent hypoglycaemia and are readily used for energy during mild exercise, there is little data indicating that feedings improve endurance during low intensity exercise. When the reliance on carbohydrate for fuel is greater, as during moderate intensity exercise, carbohydrate feedings delay fatigue by apparently slowing the depletion of muscle glycogen.

ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe concept of treating hypertension without medication is seen as an attractive alternative to the problems that can arise with the use of drug therapy. Weight loss, salt restriction, relaxation therapy, and exercise have been the non-pharmacological treatments for hypertension.The role of long term exercise in lowering resting arterial pressure in hypertension, and its use as a non-drug therapy have been studied. Epidemiological studies of athletic ability, occupation, and leisure-time activities have provided equivocal findings and the effect of training on chronic high blood pressure of hypertensives is still unclear. Further well-controlled studies (with respect to training intensities, weight loss, concurrent hypotensive medication, salt restriction, and hypertensive classification), with an emphasis on elucidating the physiological mechanisms involved, are required so that the contribution of exercise to hypertensive therapy can be determined.

ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryAlthough it is generally believed that carbohydrate and fat are the only sources of energy during physical activity, recent experimental results suggest that there are also significant alterations in protein metabolism during exercise. Depending on several factors, including intensity, duration and type of exercise, as well as prior diet, training, environment and perhaps even gender or age, these changes may be quite large.Generally, exercise promotes: (a) a decrease in protein synthesis (production) unless the exercise duration is prolonged (>4h) when increases occur; (b) either an increase or no change in protein catabolism (breakdown); and (c) an increase in amino acid oxidation. In addition, significant subcellular damage to skeletal muscle has been shown following exercise. Taken together, these observations suggest that the protein requirements of active individuals are greater than those of inactive individuals. Although the underlying reasons are different, this statement applies to both endurance and strength/power athletes.At present, it is not possible to precisely determine protein requirements. However, because deficiencies in total protein or in specific amino acids may occur, we suggest that athletes consume 1.8 to 2.0g of protein/kg of body weight/day. This is approximately twice the recommended requirement for sedentary individuals. For some athletes this may require supplementation; however, these quantities of protein can be easily obtained in a diet where 12 to 15% of the total energy is from protein.Although the effect of exercise on protein metabolism has been studied for many years, numerous questions remain. Hopefully, with the recent renewed interest in this area of study, most of these answers will soon be available.

ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

ISSN:0112-1642    

DOI:10.2165/00007256-198401060-00007

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS