摘要:

Studies of anaerobic interval training can be divided into 2 categories. The first category (the older studies) examined interval training at a fixed work-rate. They measured the time limit or the number of repetitions the individual was able to sustain for different pause durations. The intensities used in these studies were not maximal but were at about 130 to 160% of maximal oxygen uptake (V-dot2max). Moreover, they used work periods of 10 to 15 seconds interrupted by short rest intervals (15 to 40 seconds). The second category (the more recent studies) asked the participants to repeat maximal bouts with different pause durations (30 seconds to 4 to 5 minutes). These studies examined the changes in maximal dynamic power during successive exercise periods and characterised the associated metabolic changes in muscle.Using short-interval training, it seems to be very difficult to elicit exclusively anaerobic metabolism. However, these studies have clearly demonstrated that the contribution of glycogenolysis to the total energy demand was considerably less than that if work of a similar intensity was performed continuously. However, the latter studies used exercise intensities that cannot be described as maximal. This is the main characteristic of the second category of interval training performed above the minimal velocity associated with V-dot2maxdetermined in an incremental test (vV-dot2max).Many studies on the long term physiological effect of supramaximal intermittent exercise have demonstrated an improvement in V-dot2maxor running economy.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

Increasing the physical activity of typically sedentary adult populations is at the forefront of the public health agenda. This review addresses the challenges in defining and measuring physical activity in this target group, for a number of purposes, namely, scientific or academic inquiry, surveillance, clinical application and programme evaluation. First, we clarify the conceptual distinctions between the terms sedentarism, physical inactivity, physical activity and energy expenditure. Next, we review and compare the utility of different approaches for quantifying and expressing physical activity in these populations. Physical activity in typically sedentary populations is most likely a simple pattern of behaviour that has been largely obscured by existing measures and its expression as energy expenditure. Existing self-report methods are practical, but suffer from floor effects and recall bias. Walking, the most important activity to assess in this target group, is very difficult to measure through self-report methods. Motion sensors are more appropriate for quantifying physical activity behaviours in typically sedentary populations. Of the 2 types of motion sensors − the accelerometer and the pedometers − the latter is more appealing because it is both an affordable and a ‘good enough’ measure of physical activity, specifically ambulatory activity. Although a common measurement approach would greatly facilitate our understanding of physical activity behaviour patterns, the selection of an approach ultimately depends on the purpose of the study and to a great extent, its budget. Researchers, clinicians and practitioners interested in accurately capturing the lower end of the continuum of physical activity (that is characteristic of sedentary populations) must thoughtfully consider the relative advantages and disadvantages of the available approaches.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

This review of the epidemiological evidence regarding physical activity and cardiovascular disease (CVD) provides substantial evidence from many different populations that leisure time physical activity is associated with reduced risk of coronary heart disease (CHD) and cardiovascular mortality in both men and women and in middle-aged and older individuals. Physical activity appears to be a critical factor in both primary and secondary prevention of CHD. The studies indicate a dose-response relationship between overall physical activity and CVD, which is linear at least up to a certain level of activity. Prospective studies suggest that physical activity is also associated with reduced risk of stroke. The mechanisms underlying the protective effect of physical activity on CVD are still unclear. In recent years, the view that physical activity has to be vigorous to achieve a reduction in risk of CHD has been questioned. Overall, the evidence points to the benefit of continued regular moderate physical activity which does not need to be strenuous or prolonged and includes daily leisure activities such as walking or gardening which are readily attainable by large sections of the population. Taking up regular light or moderate physical activity in middle or older age confers significant benefit for CVD and all-cause mortality.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS

摘要:

Cytokines are soluble glycoproteins that are produced by and mediate communication between and within immune and nonimmune cells, organs and organ systems throughout the body. Pro- and anti-inflammatory mediators constitute the inflammatory cytokines, which are modulated by various stimuli, including physical activity, trauma and infection. Physical activity affects local and systemic cytokine production at different levels, often exhibiting striking similarity to the cytokine response to trauma and infection.The present review examines the cytokine response to short term exercise stress, with an emphasis on the balance between pro- and anti-inflammatory mechanisms and modulation of both innate and specific immune parameters through cytokine regulation. The effects of long term exercise on cytokine responses and the possible impact on various facets of the immune system are also discussed, with reference to both cross-sectional and longitudinal studies of exercise training. Finally, the validity of using exercise as a model for trauma and sepsis is scrutinised in the light of physiological changes, symptomatology and outcome, and limitations of the model are addressed.Further studies, examining the effect of exercise, trauma and infection on novel cytokines and cytokine systems are needed to elucidate the significance of cytokine regulation by physical activity and, more importantly, to clarify the health implications of short and long term physical activity with respect to overall immune function and resistance to infection.

ISSN:0112-1642    

出版商:ADIS    

年代:2001

数据来源: ADIS