H.-J. Appell

Exercise, Muscle Damage and Fatigue

SummaryFatigue as a functional sign and muscle damage as a structural sign can be observed after prolonged exercise like marathon running or after strenuous exercise, especially with the involvement of eccentric contractions. For fatigue due to prolonged exercise, hypoxic conditions and the formation of free oxygen radicals seem to be of aetiological importance, resulting in an elevated lysosomal activity. Eccentric exercise of high intensity rather results in a mechanical stress to the fibres. Although these different mechanisms can be discerned experimentally, both result in similar impairments of muscle function. A good training status may attenuate the clinical signs of fatigue and muscle damage. The symptoms and events occurring during delayed onset of muscle soreness (DOMS) can be explained by a cascade of events following structural damage to muscle proteins.

Skeletal Muscle Pathways of Contraction-Enhanced Glucose Uptake

Muscle contraction acutely increases glucose transport in both healthy and type 2 diabetic individuals. Since glucose uptake during muscle contraction has been observed in the absence of insulin, the existence of an insulin-independent pathway has been suggested to explain this phenomenon. However, the exact mechanism behind the translocation of GLUT4 vesicles through the sarcolemma during muscle contraction is still unknown. Some substances, such as AMPK and calcium activated proteins, have been suggested as potential mediators but the exact mechanisms of their involvement remain to be elucidated. A hypothetical convergence point between the insulin cascade and the potential pathways triggered by muscle contraction has been suggested. Therefore, the earliest concept that two different routes exist in skeletal muscle has been progressively modified to the notion that glucose uptake is induced by muscle contraction via components of the insulin pathway. With further consideration, increased glucose uptake and enhanced insulin sensitivity observed during/after exercise might be explained by a metabolic- and calcium-dependent activation of several intermediate molecules of the insulin cascade. This paper aimed to review the literature in order to examine in detail these concepts behind muscle contraction-induced glucose uptake.

Administration of tourniquet

One hindlimb of mice was subjected to 60, 90 and 120 min ischemia by application of a tourniquet followed by a 60-min reperfusion period. An additional experimental group received a tourniquet for 90 min without subsequent reperfusion. The soleus muscle (from the contralateral side also as control) was removed and evaluated for muscle weight, protein weight, protein content, and glutathione concentrations. Ischemia alone without subsequent reperfusion did not produce significant changes. With postischemic reperfusion, the protein content and muscle weight increased, probably because of an increased capillary permeability, leading to muscle edema. Oxidative stress was also present during reperfusion, correlating well with the changes in protein content. The intensity of these alterations appeared to depend on the period of ischemia.

Involvement of advanced glycation end products in the pathogenesis of diabetic complications: the protective role of regular physical activity

Advanced glycation end products (AGEs) may play an important role in the pathogenesis of chronic diabetic complications and in the natural process of biological aging. In fact, maintained hyperglycaemia favours the formation of AGEs at the tissue level in diabetic patients, which may influence the triggering of different chronic pathologies of diabetes such as retinopathy, nephropathy, neuropathy and macro- and micro-vascular diseases. Moreover, the literature has also demonstrated the involvement of AGEs in biological aging, which may explain the accelerated process of aging in diabetic patients. The practice of regular physical activity appears to positively influence glycaemic control, particularly in type 2 diabetes mellitus patients. This occurs through the diminution of fasting glycaemia, with a consequent reduction of glycation of plasmatic components suggested by the normalisation of HbA1c plasmatic levels. This exercise-induced positive effect is evident in the blood of diabetic patients and may also reach the endothelium and connective tissues of different organs, such as the kidneys and eyes, and systems, such as the cardiovascular and nervous systems, with a local reduction of AGEs production and further deceleration of organ dysfunction. The aim of this paper was to review the literature concerning this topic to coherently describe the harmful effects of AGEs in organ dysfunction induced by diabetes in advanced age as well as the mechanisms behind the apparent protection given by the practice of regular physical activity.

Regular physical exercise in patients with type II diabetes mellitus

It is widely accepted that regular physical exercise helps diabetic patients control blood glucose, reduce cardiovascular risk factors, and prevent other related complications. In spite of the undoubted benefits of regular physical exercise, diabetic patients with chronic complications should be aware of potential hazards of practicing exercise. To avoid some harmful consequences of acute exercise, it is necessary to adopt a vigilant attitude with these risk patients and to carefully adjust type and intensity of exercise to the individual situation. This article intends to summarize and analyze the current literature concerning the preventive and therapeutic effects of regular exercise in diabetic patients, pointing out its physiological influence on blood glucose regulation, and to analyze the potential risks of acute physical exercise and the precautions given to patients with a variety of complications.

Characteristics of the gluteus medius muscle in an asymptomatic patient with radiographic signs of coxarthrosis

This case study describes the micromorphology and some biochemical features of gluteus medius muscle in a 79-year-old woman with radiographic signs of coxarthrosis but with no clinical symptoms who initially was admitted in the orthopaedic emergency service with a non-displaced subcapital fracture of the femoral neck due to a domestic accident (fall). The X-ray of the hip showed some characteristic features of coxarthrosis, classified grade 2 of the Kellgren criteria. After informed consent, it was decided to carry out the functional evaluation according to the indexes of Lequesne and WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index) and to take a biopsy of the gluteus medius muscle for microscopical examination and myosin heavy chain isoform identification during hip replacement surgery. For the Lequesne Index (score 0–24), the total score was 0, and for the WOMAC (score 0–96), the total score was also 0, both speaking in favour of full joint and muscle function. All the structural features observed in muscle were considered not to have any pathological relevance. The composition of the myosin heavy chains in the gluteus medius muscle was 48% MHC I, 41% MHC IIa, and 11% MHC IIx. The muscle characteristics do not support earlier concepts about muscle weakness as a predisposing factor for osteoarthritis. It is moreover concluded that the diagnosis should rather consider clinical symptoms than radiographic signs of osteoarthritis.RésuméCette étude de cas décrit la micromorphologie et quelques caractéristiques biochimiques du muscle gluteus medius (moyen fessier), chez une patiente âgée de 79 ans avec des signes radiographiques de coxarthrose mais sans symptomatologie, qui avait été admise dans le service d’urgence avec une fracture sous-capitale alignée du col du fémur, à la suite d’un accident domestique (chute). La radiographie de la hanche montrait quelques signes de coxarthrose, (degré 2 de Kellgren). Après information et acceptation de la patiente, on a effectué en utilisant les Index de Lequesne et WOMAC, l’évaluation fonctionnelle ainsi qu’une biopsie du muscle gluteus medius pendant l’intervention chirurgicale pour examen microscopique et identification des isomorphes de la chaîne lourde de myosine. Pour l’Index de Lequesne (score 0–24), le total a été 0 et pour celui de WOMAC (score 0–96), le score total a aussi été zéro, les deux indices étant favorables à une bonne fonctionnalité musculaire et articulaire. Toutes les caractéristiques structurales observées ont été considérées sans relevance pathologique. La composition des chaînes lourdes de myosine dans le muscle gluteus medius a été de: 48% MHC I, 41% MHC II et 11% MHC IIx. Les caractéristiques du muscle n’appuient pas l’hypothèse que la dysfonction musculaire serait un facteur qui prédisposerait à l’arthrose. On a conclut également que le diagnostic de coxarthrose doit plus prendre en compte les symptômes cliniques plutôt que les signes radiographiques d’arthrose.