摘要:

A common belief in exercise physiology is that fatigue during exercise is caused by changes in skeletal muscle metabolism. This ‘peripheral’ fatigue results either from substrate depletion during submaximal exercise or metabolite accumulation during maximal exercise in the exercising muscles. However, if substrate depletion alone caused fatigue, intracellular ATP levels would decrease and lead to rigor and cellular death. Alternatively, metabolite accumulation would prevent any increase in exercise intensity near the end of exercise. At present, neither of these effects has been shown to occur, which suggests that fatigue may be controlled by changes in efferent neural command, generally described as ‘central’ fatigue.In this review, we examine neural efferent command mechanisms involved in fatigue, including the concepts of muscle wisdom during short term maximal activity, and muscle unit rotation and teleoanticipation during submaximal endurance activity. We propose that neural strategies exist to maintain muscle reserve, and inhibit exercise activity before any irreparable damage to muscles and organs occurs. The finding that symptoms of fatigue occur in the nonexercising state in individuals with chronic fatigue syndrome indicates that fatigue is probably not a physiological entity, but rather a sensory manifestation of these neural regulatory mechanisms.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

Renal replacement treatment options are life-saving treatments for patients with end-stage renal disease (ESRD). However, prolonged survival in patients with ESRD is associated with various functional and morphological disorders from almost all systems. Anaemia, deconditioning, cardiac dysfunction, impairment of cardiac autonomic control and skeletal muscle weakness and fatigue, primarily because of ‘uraemic’ myopathy and neuropathy, are the main predisposing factors for their poor functional ability.Physical training is being recommended as a complementary therapeutic modality. There are generally 3 methods of exercise training applied in patients with ESRD:the supervised outpatient programme that is held in a rehabilitation centre;a home exercise rehabilitation programme; andexercise rehabilitation programme during the first hours of the haemodialysis treatment in the renal unit.All the available training data show that the application of an exercise training programme in patients with ESRD enhances their physical fitness. This improvement is due to central and mainly peripheral adaptations. Exercise training in these patients increases aerobic capacity, causes favourable left ventricular functional adaptations, reduces blood pressure in patients with hypertension, modifies other coronary risk factors, increases the cardiac vagal activity and suppresses the incidence of cardiac arrhythmias. Moreover, exercise training has beneficial effects on muscle structural and functional abnormalities. These central and peripheral adaptations to exercise training cause an increase in their functional capacity and offer them a chance of a better quality of life. Moreover, exercise training improves exercise tolerance of renal post-transplant patients.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

Sport injuries are unwanted adverse effects accompanying participation in sports. In a wide variety of sports the most common location of injury is the ankle, frequently resulting from a forced plantar flexed inversion of the foot exceeding the physiological range of motion (ROM). Historically the purpose of external support systems is to prevent acute ankle injuries by restricting abnormal ankle ROM. It is believed that a superior restrictive effect also implies a superior preventive effect.The purpose of this review was to examine the literature regarding the restricting effect of adhesive taping, prophylactic ankle stabilisers (PAS) and high-top shoes on ankle ROM. It has been found that tape restricts ankle eversion and inversion ROM significantly following application. However, tape loosens significantly following standardised exercise and sports activities. Studies regarding PAS reported that both semi-rigid and nonrigid stabilisers give a significant post-application restriction of ankle inversion motion. The nonrigid stabilisers show loosening over time during exercise, while the semi-rigid stabilisers maintain their restrictive effect over the same time span. High-top shoes in comparison to low-top shoes are more effective in restricting mechanically imposed ankle inversion ROM. Low-top shoes, however, also limit mechanically imposed ankle inversion stress with the ankle in the position in which ankle injury occurs most frequently. One must keep in mind, however, that a superior mechanical restriction of ankle ROM does not necessarily imply a superior preventive effect. Only well-controlled randomised studies can show such an effect, and these studies have shown a reduction of ankle injury incidence for all 3 prophylactic measures reviewed.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

The aim of this review article is to identify the main metabolic factors which have an influence on the energy cost of running (Cr) during prolonged exercise runs and triathlons. This article proposes a physiological comparison of these 2 exercises and the relationship between running economy and performance. Many terms are used as the equivalent of ‘running economy’ such as ‘oxygen cost’, ‘metabolic cost’, ‘energy cost of running’, and ‘oxygen consumption’. It has been suggested that these expressions may be defined by the rate of oxygen uptake (V-dot2) at a steady state (i.e. between 60 to 90% of maximal V-dot2) at a submaximal running speed.Endurance events such as triathlon or marathon running are known to modify biological constants of athletes and should have an influence on their running efficiency. The Cr appears to contribute to the variation found in distance running performance among runners of homogeneous level. This has been shown to be important in sports performance, especially in events like long distance running. In addition, many factors are known or hypothesised to influence Cr such as environmental conditions, participant specificity, and metabolic modifications (e.g. training status, fatigue). The decrease in running economy during a triathlon and/or a marathon could be largely linked to physiological factors such as the enhancement of core temperature and a lack of fluid balance. Moreover, the increase in circulating free fatty acids and glycerol at the end of these long exercise durations bear witness to the decrease in Cr values. The combination of these factors alters the Cr during exercise and hence could modify the athlete's performance in triathlons or a prolonged run.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

In-line skating has remained a popular recreational activity all over the world. The number of injuries seemingly reached a plateau in the late 1990s. However, there are still more injuries caused by in-line skating than from skateboarding, hockey or lacrosse and rugby. In 1997, the estimated annual cost of medical treatment for these injuries in the US was over $US4 billion.Adolescence still represents the largest group of skaters, both in participation and injury. Although 10- to 14-year-olds account for 60% of injuries, in 1996 the US Consumer Product Safety Commission reported nearly 1500 injuries in individuals 65 years and over. Risk factors for injury include inexperience, aggressive skating and amount of time spent skating. There are also more recent data to suggest that self-reported expert skaters are more likely to sustain an injury.Reluctance to use personal protective equipment (PPE) by in-line skaters remains high. The general consensus is that PPE is effective in reducing the incidence and severity of in-line skating injuries. Therefore, efforts should be made to increase awareness of risk factors for injury in all skaters; to increase use of safety equipment; to provide safe environments for skating; and to legislate skating laws that will protect skaters from injuries.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS