摘要:

SummaryA comparison of the literature quantifying the energy expended during ambulation of healthy individuals and those with amputation of the lower extremity is difficult as study parameters and methods are inconsistent. However, the energy cost of ambulation is greater for amputees than for nonamputees. Ascending level of amputation appears to be associated with increasing metabolic demand. There appears to be a difference in energy cost of ambulation following different surgical procedures. The literature regarding energy cost of ambulating with different lower-extremity prostheses is equivocal, with the exception of the contoured adducted trochanteric-controlled alignment method (CAT-CAM) socket for above-knee amputees and the new energy-storing (Proteor™) foot for traumatic below-knee amputees, which may decrease energy expenditure during ambulation. Therefore, it is reasonable to recommend that energy cost of ambulation be considered when deciding on the most efficacious surgical procedure, and metabolic efficiency of gait be considered when selecting prostheses most suitable for lower-extremity amputees.Though limited research is currently available, it appears that training or physical conditioning for the lower-extremity amputee, particularly with cardiopulmonary or vascular insufficiency, may decrease the metabolic cost of ambulation. More research is needed regarding the benefits of aerobic exercise and the safest, most effective exercise regimens for reducing metabolic costs of ambulation in lower-extremity amputees.

ISSN:0112-1642    

DOI:10.2165/00007256-199520040-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryIt is widely accepted that a structural organisation favouring interaction between functionally-related enzymes is required for the economy and efficiency of metabolic reactions. Many functionally-related enzymes have been shown to be reversibly bound to cellular structures and to other enzymes at the sites where they are required. Resulting from this binding, close structural proximity and concentration of enzymes, a microenvironment is generated where the product of one enzyme is the substrate of the other. This reduces the diffusion distance for the substrate, saturates binding sites with maximal speed and, as a final outcome, increases the efficiency and economy of function behind these metabolic reactions. Available data indicate that the above-described association between adenosine triphosphatase (ATPase) and enzymes regenerating ATP has an important role in the regulation of ATPase function.A general consensus exists among published studies that the concentration of ATP ([ATP]) is not significantly decreased in fatigued muscle, even in those with severely diminished power output. However, in studies with isolated perfused hearts it has been possible to significantly reduce [ATP]in muscle cells without compromising mechanical activity. An explanation for this discrepancy is connected with local ATP regeneration in the vicinity of ATPase. Furthermore, when ATP regeneration is unable to balance ATP consumption a critical drop in the free energy of ATP hydrolysis is avoided by down-regulation of ATP consumption.The main function of local ATP regeneration is to maintain a low concentration of adenosine diphosphate ([ADP]), and the ADP/ATP ratio in the vicinity of the ATP-binding site of ATPase that is a prerequisite for high thermodynamic efficiency of ATP hydrolysis. Close proximity of creatine kinase and glycolytic enzymes to ATPase and high-affinity binding of substrates generate an ATPase microenvironment, where ADP and ATP are not in free equilibrium with those adenine nucleotides in the surrounding medium. In the physiological range of operation for important cellular ATPases (free energy change of 55 to 60 kJ/mol ATP) only a small fraction of energy, available in ATP, can be utilised, provided that no ATP regeneration takes place. However, ATP regeneration allows utilisation of most of the regenerating capacity, before ATP hydrolysis drops below the critical 55 kJ/mol.The importance of local ATP regeneration increases in parallel with an increase in the rate of ATPase turnover. Furthermore, the time during which cells can maintain high rates of ATP hydrolysis depends on the capacity of mechanisms for local ATP regeneration, provided that ATPase is not inhibited by factors other than the reaction products. When this capacity is exhausted and the ADP/ATP ratio starts to increase, a further decrease in the free energy of ATP hydrolysis is avoided by down-regulation of ATP consumption. Because cellular ATPases, and especially sarcoplasmic reticulum Ca++-ATPase, require substantial amounts of the free energy available from ATP hydrolysis, this down-regulation of ATP hydrolysis is directed to maintain that level of structural organisation (primarily ionic gradients) which is essential for living cells. Consequently, the biological significance of this down-regulation is to prevent an increase in entropy and irreversible structural changes.

ISSN:0112-1642    

DOI:10.2165/00007256-199520040-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryThe ultimate goal of comprehensive rehabilitation in individuals with spinal cord injury (SCI) has shifted over time from an extension of their life expectancy to attainment of an optimal level of independent living and quality of life. After World War II, the important influence of sport and exercise upon the course of rehabilitation following SCI was recognised. Nonetheless, 5 decades later, there remains a lack of understanding of how an exercise programme can contribute to an improvement of quality of life among individuals with SCI. In future, attention should be directed toward avoidance of secondary impairments, disabilities and handicaps. The World Health Organization model of disablement provides a suitable framework for addressing this issue.The most common benefits of exercise are biological in nature. They target a reduction in secondary impairments (loss of cardiorespiratory, and muscular function, metabolic alterations and systemic dysfunctions). This in turn could minimise the development of disabilities and the appearance of such handicaps as loss of mobility, physical dependence and poor social integration. A lack of physical fitness for specific tasks can be a serious obstacle to autonomy following SCI. In a very short period of time, physical deconditioning can significantly decrease quality of life in individuals with SCI, ultimately placing them in a state of complete dependency.Quality of life is closely associated with independent living and, increasingly, it is a key outcome when measuring the success of rehabilitation. Consequently, research designs that examine the impact of exercise upon individuals with disabilities should not only include objective outcome measures, but also subjective measures relating to life-satisfaction and quality of life.

ISSN:0112-1642    

DOI:10.2165/00007256-199520040-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryAn imbalance between the overall strain experienced during exercise training and the athlete’s tolerance of such effort may induce overreaching or overtraining syndrome. Overtraining syndrome is characterised by diminished sport-specific physical performance, accelerated fatiguability and subjective symptoms of stress. Overtraining is feared by athletes yet there is a lack of objective parameters suitable for its diagnosis and prevention.In addition to the determination of substrates (e.g. lactate, ammonia and urea) and enzymes (e.g. creatine kinase), the possibilities for monitoring of training by measuring hormonal levels in blood are currently being investigated.Endogenous hormones are essential for physiological reactions and adaptations during physical work and influence the recovery phase after exercise by modulating anabolic and catabolic processes. Testosterone and cortisol are playing a significant role in metabolism of protein as well as carbohydrate metabolism. Both are competitive agonists at the receptor level of muscular cells. The testosterone/cortisol ratio is used as an indication of the anabolic/catabolic balance. This ratio decreases in relation to the intensity and duration of physical exercise, as well as during periods of intense training or repetitive competition, and can be reversed by regenerative measures. Correlations have been noted with the training-induced changes of strength. However, it seems more likely that the testosterone/cortisol ratio indicates the actual physiological strain in training, rather than overtraining syndrome.The sympatho-adrenergic system might be involved in the pathogenesis of overtraining. Overtraining appears as a disturbed autonomic regulation, which in its parasympathicotonic form shows a diminished maximal secretion of catecholamines, combined with an impaired full mobilisation of anaerobic lactic reserves. This is supposed to lead to decreased maximal blood lactate levels and maximal performance. Free plasma adrenaline (epinephrine) and noradrenaline (norepinephrine) may provide additional information for the monitoring of endurance training. While prolonged aerobic exercise conducted at intensities below the individual anaerobic threshold lead to a moderate rise of sympathetic activity, workloads exceeding this threshold are characterised by a disproportionate increase in the levels of catecholamines. In addition, psychological stress during competitive events is characterised by a higher catecholamines to lactate ratio in comparison with training exercise sessions. Thus, the frequency of training sessions with higher anaerobic lactic demands or of competition, should be carefully limited in order to prevent overtraining syndrome.In the state of overtraining syndrome and overreaching, respectively, an intraindividually decreased maximum rise of pituitary hormones (corticotrophin, growth hormone), cortisol and insulin has been found after a standardised exhaustive exercise test performed with an intensity of 10% above the individual anaerobic threshold. This disturbed stress-response corresponds to findings with insulin-induced hypoglycaemia in overtraining suggesting an impaired hypothalamic regulation.However, the role of hormones in the recovery phase and their effect on the receptor and intracellular level remain to be better established. Reference values indicating a ‘normal’ exercise tolerance as well as easier and less expensive laboratory methods are still lacking. External factors influencing the hormonal blood levels require well-standardised sampling conditions which are often difficult to realise in the training environment. The impaired exercise-induced maximal increase of selected hormones and the potential consideration of the psychological stress component by hormonal measurements, however, represent interesting basic findings which encourage future investigations.

ISSN:0112-1642    

DOI:10.2165/00007256-199520040-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryAnkle sprains are a common sports injury that can cause significant, chronic disability. Studies aimed at prevention through the use of footwear have focused on the biomechanical aspects of foot and ankle anatomy, proprioceptive input of the foot/ankle complex, external stresses applied to the joint, and shoe traction. These studies support the use of high top shoes for ankle sprain prevention because of their ability to limit extreme ranges of motion, provide additional proprioceptive input and decrease external joint stress. Despite this biomechanical evidence, clinical trials are inconclusive as to the clinical benefit of high top shoes in the prevention of ankle sprains. Further study is necessary to delineate the benefits of shoe designs for ankle sprain prevention.

ISSN:0112-1642    

DOI:10.2165/00007256-199520040-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS