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Chronobiology from theory to sports practice

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... In a person unaccustomed to morning exercise, voluntary and artificially evoked muscle strength (maximum and explosive) has been repeatedly reported to be on average 5-10% lower in the morning hours compared to the rest of the day (e.g., Araujo et al. 2011;Callard et al. 2000;Castaingts et al. 2004;Coldwells et al. 1994;Deschenes et al. 1998;Gauthier et al. 1996;Giacomoni et al. 2005, Guette et al. 2005, Mora-Rodrıguez et al. 2012Nicolas et al. 2005., Sedliak et al. 2008. This phenomenon has been termed as 'morning neuromuscular deficit' due to the fact that that inputs from the central nervous system are, at least partly, an important source (for a review see Sedliak 2013). ...
Accumulation of DNA is essential for muscle growth, yet mechanisms of androgen-induced DNA accretion in skeletal muscle are unclear. The purpose of this study was to determine whether androgen receptors (AR) are present in cultured skeletal muscle satellite cells and myotubes and examine the effects of testosterone on satellite cell proliferation and differentiation. Immunoblot analysis using polyclonal AR antibodies (PG-21) revealed an immunoreactive AR protein of approximately 107 kDa in porcine satellite cells and myotubes. Immunocytochemical AR staining was confined to the nuclei of satellite cells, myotubes, and muscle-derived fibroblasts. Administration of 10(-7) M testosterone to satellite cells, myotubes, and muscle-derived fibroblasts increased immunoreactive AR. In satellite cells and myotubes, AR increased incrementally after 6, 12, and 24 h of exposure to testosterone. Testosterone (10(-10) - 10(-6) M), alone or in combination with insulin-like growth factor I, basic fibroblast growth factor, ...
This study was conducted in five provinces and food consumption, physical activity types and duration for 3 consecutive days were recorded in the questionnaire together with some general characteristics of 750 (320 males, 430 females) adults who were on fast during Ramadan at time of interview. One hundred and eighty-seven subjects had some type of health problems, among whom 60.4% were using drugs, and 31.6% were on diets; however, during Ramadan 9.7 and 18.8% of the subjects dropped taking drugs and did not regularly keep on diets, respectively. During the fasting time, from dawn to sunset, 34.3% of the subjects developed some behavioural disturbances, such as feeling tired and being unwilling to work. Although the meal consumed at dawn consisted of foods that were usually eaten at breakfast, the meal consumed at sunset consisted of a great variety of foods. Calcium intake was the most insufficiently consumed nutrient. It was observed that the daily energy intakes were less than the expenditures both in males and females. Further research should be done on the effects of fasting in health and disease.
Humans are diurnal by nature but modern industrialized societies must function throughout the 24 hours of the day. Not only are emergency services required to be able to act at any time, but communications, commerce and industrial processes also never cease their operations. In the military sphere in particular, round-the-clock capability is required. Whereas these processes have been accompanied by an increasing replacement of humans by technology, if only because humans are too slow, expensive, and unreliable, our species still is required to tend such systems and act in relation to the information they give or require. The role of humans has tended to change, therefore, from the that of providing brute strength and even intellectual input to one of vigilance and the minding of machines.