ISSN:0112-1642    

DOI:10.2165/00007256-199417010-00001

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryWorking muscle plays a central role in the control of lipid metabolism. Increased physical activity induces a number of positive changes in the metabolism of lipoproteins: serum triglycerides are lowered by the increased lipolytic activity and the production of native high density lipoprotein (HDL) particles is increased. The increased lecithin: cholesterol acyltransferase activity leads to an increased production of HDL2, which in addition is catabolised more slowly due to a decreased activity of hepatic lipase. The 3 effects explain the increased HDL levels of endurance trained individuals. These effects have been demonstrated in cross-sectional as well as longitudinal studies by different groups, and can be induced by training, independent of changes in body weight. The influence of endurance activity on the quality and quantity of low density lipoprotein (LDL) particles is a further reason for the antiatherogenic potential of increased physical activity. It has been shown by several groups that small dense LDL particles represent a particular risk factor for atherosclerosis. Recent studies presented strong evidence that LDL level and composition can be influenced favourably by physical activity. In addition to the direct influence of physical activity on lipids and lipoproteins, physical exercise may improve the disturbances of haemorheological factors, particularly those associated with hypertriglyceridaemia.In conclusion, there is increased evidence that physical activity is able to favourably influence all 3 components of the atherogenic lipoprotein phenotype: the HDL concentration increases, the concentration of small dense LDL decreases, and serum triglycerides are reduced.

ISSN:0112-1642    

DOI:10.2165/00007256-199417010-00002

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummarySkeletal muscle tissue is sensitive to the acute and chronic stresses associated with resistance training. These responses are influenced by the structure of resistance activity (i.e. frequency, load and recovery) as well as the training history of the individuals involved. There are histochemical and biochemical data which suggest that resistance training alters the expression of myosin heavy chains (MHCs). Specifically, chronic exposure to bodybuilding and power lifting type activity produces shifts towards the MHC I and IIb isoforms, respectively. However, it is not yet clear which training parameters trigger these differential expressions of MHC isoforms. Interestingly, many programmes undertaken by athletes appear to cause a shift towards the MHC I isoform. Increments in the cross-sectional area of muscle after resistance training can be primarily attributed to fibre hypertrophy. However, there may be an upper limit to this hypertrophy. Furthermore, significant fibre hypertrophy appears to follow the sequence of fast twitch fibre hypertrophy preceding slow twitch fibre hypertrophy. Whilst some indirect measures of fibre number in living humans suggest that there is no interindividual variation, postmortem evidence suggests that there is. There are also animal data arising from investigations using resistance training protocols which suggest that chronic exercise can increase fibre number. Furthermore, satellite cell activity has been linked to myotube formation in the human.However, other animal models (i.e. compensatory hypertrophy) do not support the notion of fibre hyperplasia. Even if hyperplasia does occur, its effect on the cross-sectional area of muscle appears to be small. Phosphagen and glycogen metabolism, whilst important during resistance activity appear not to normally limit the performance of resistance activity. Phosphagen and related enzyme adaptations are affected by the type, structure and duration of resistance training. Whilst endogenous glycogen reserves may be increased with prolonged training, typical isotonic training for less than 6 months does not seem to increase glycolytic enzyme activity. Lipid metabolism may be of some significance in bodybuilding type activity. Thus, not surprisingly, oxidative enzyme adaptations appear to be affected by the structure and perhaps the modality of resistance training. The dilution of mitochondrial volume and endogenous lipid densities appears mainly because of fibre hypertrophy.

ISSN:0112-1642    

DOI:10.2165/00007256-199417010-00003

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryDespite the widespread dissemination of information concerning the negative health consequences associated with sedentary living, adult physical activity in many industrialised nations remains well below recommended levels. Approximately 50% of individuals who start an aerobic exercise programme will stop within the first 6 months, even though it is well known that to obtain the health benefits associated with physical activity, participation must be maintained. Programmes involving the use of behaviour management techniques appear to increase short term adherence to exercise. Recently, an adherence rate of greater than 95% over 6 months was achieved in a large group of university employees who participated in aerobic training using a ‘behavioural treatment packages’ approach. Unfortunately, inconsistencies in the literature on definitions and measurement of adherence make valid comparisons among studies difficult. Also, long term follow-up of behavioural intervention methods and their effect on exercise adherence is generally lacking. It is likely that strategies to increase physical activity participation in the general population will demand multiple levels of intervention (personal, organisational, environmental and societal) if they are to succeed in the long term.

ISSN:0112-1642    

DOI:10.2165/00007256-199417010-00004

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryShoulder pain is a common complaint amongst tennis players. The anatomy of the shoulder girdle is complex and defining the exact pathology that accounts for shoulder pain in tennis players can be difficult. Impingement syndrome and glenohumeral instability are the 2 most common causes of shoulder pain in tennis players. Tennis players with impingement syndrome typically present with pain, especially during overhead strokes and serves. The impingement test helps to confirm the diagnosis. Treatment focuses on restoring any motion and strength deficits and anterior acromioplasty with repair of rotator cuff tears for patients who do not respond to nonoperative care. Tennis players with instability present with pain and a sensation of shoulder ‘slipping’. Treatment emphasises rotator cuff and scapular muscle strengthening and surgical stabilisation of the capsulo-labral complex for patients who fail a rehabilitation programme. Prevention of injury in tennis players depends on maintaining flexibility, strength and synchrony among the glenohumeral and scapular muscles.

ISSN:0112-1642    

DOI:10.2165/00007256-199417010-00005

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS

摘要:

SummaryStress fracture of the tarsal navicular bone is now frequently recognised. The majority of navicular stress fractures are partial fractures in the sagittal plane. They occur mainly in track and field athletes. A number of theories regarding the aetiology of this fracture have been proposed.Athletes with a history of vague, activity-related midfoot pain, with associated tenderness over the dorsal proximal navicular (’N’ spot) should be suspected of having a navicular stress fracture. Plain radiography frequently fails to demonstrate the fracture, thus radionuclide scanning is the investigation of choice to detect navicular stress injury. A computed tomography (CT) scan should be performed to confirm the presence of the fracture.Various methods of treatment have been employed. A minimum of 6 weeks of strict non-weightbearing cast immobilisation is the treatment of choice. After removal of the cast, a further 6 week programme of rehabilitation with a graduated return to activity, joint mobilisation and soft tissue massage is required. Surgery for nonunion or delayed union is rarely required if initial treatment is appropriate.

ISSN:0112-1642    

DOI:10.2165/00007256-199417010-00006

出版商:Springer International Publishing    

年代:2012

数据来源: ADIS