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Summary
Objectives
The aim of this paper is to emphasize the possible relationships established between estrogens and physical exercise and concerning bone metabolism. Nitric oxide (NO) might play an important role in such relationships.Topics
Cellular metabolism of NO, as well as NO effects upon osteoblasts and osteoclasts have been summarized. Several studies indicate that NO deficiency might be implicated in various vascular diseases observed in post-menopausal women. Other works also indicate that NO deficiency induced by cessation of ovarian activity might be responsible for osteopenia associated with this condition. Thus, decreased production of NO would be responsible both for post-menopausal osteoporosis as well as for osteopenia sometimes observed in amenorrheic athletes. Moreover osteoblastic response to mechanical stimulation might implicate estrogenic receptor(s). The role of these receptors in the regulation of NO synthesis is still unknown. 相似文献2.
Aim – Study was then to investigate hydration influence on exercise-induced GHh secretion.Methods and results – Seven healthy men underwent a submaximal rectangular cycling exercise for 30 minutes to 150 watts during two sessions. A first one without any water intake and a second one with ingestion of spring water corresponding to the volume of water lost during the first session. Plasma volume decrease was significantly higher during the first session (p < 0.05). Total GH secretion was significantly lower during this session (p < 0.05).Conclusion – A moderate dehydration decreases exercise-induced GH response. Thus, hypovolemia may exert a negative feed back on GH secretion, during exercise. 相似文献
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Aim – The aim of the present study was to investigate the VO2 uptake slow component in prepubertal children of different aerobic capacity during high intensity exercise.Method – Twenty three (12 well-trained and 11 untrained) prepubertal children took part in two constant-power tests performed at intensities corresponding to 80% of the anaerobic threshold and 90% of maximal aerobic power. VO2 kinetics during both constant-power tests was determine using a monoexponential + linear term model.Results/conclusion – Our results demonstrated the existence of a slow component during heavy intensity exercise in prepubertal children, as previously described in adults. The magnitude of this slow component did not differ between trained swimmers and untrained children exercising at the same relative intensity, provided that the whole VO2 response was considered. 相似文献
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Aims – Investigate the influence of exercise training on the aerobic and anaerobic capacities of young swimmers.Methods – Ten male swimmers aged 15.2 ± 3.8 years participated: five sprint specialists and five middle-distance specialists. Each subject performed, an arm ergocycle, two laboratory tests, a maximal incremental exercise test and a force–velocity test, once in February (T1) and then again in June (T2).Results – For all subjects combined (n=10), the results showed a significant increase in maximal anaerobic power (p < 0.01) between T1 and T2. Aerobic capacity did not change significantly between the two tests in either group.Conclusion – This study demonstrates the interest of evaluating aerobic and anaerobic capacity in young swimmers during arm exercise. The change in results over the 5-month period between the two tests indicates the importance of scheduling exercise tests during the course of athletic training programs. 相似文献
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V. -A. Bricout 《Science & Sports》2003,18(6):293-295
Aim. – Verify the sensibility of a standardised overtraining questionnaire during a weekly observation in a sport population.Methods and results. – The experiment was carried out in 12 athletes, 20–23 years old, students at the University in Licence STAPS, with a standardised overtraining questionnaire given every week during 8 weeks. Results were analysed individually and for the total population. Those showed that overtraining questionnaire could allow individualised training programs, and could provide some pertinent information on sleep quality and physical condition for each athlete. For the coach, the overtraining questionnaire permits to identify some fatigue state, consecutively to training variations. On the total population, the analysis of overtraining questionnaire showed some items more reliable than other.Conclusion. – This questionnaire was very interesting for coaches, allowing a good individualisation of the training program. Nevertheless, this questionnaire presents intricate statistical analysis when given at high frequency. 相似文献
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J. -C. Chatard D. Atlaoui V. Pichot C. Gourn M. Duclos Y. -C. Guzennec 《Science & Sports》2003,18(6):302-304
Introduction. – A short questionnaire of fatigue, urinary cortisol/cortisone ratio and heart rate variability were measured in 14 elite swimmers during heavy, light and moderate training periods.Results. – The questionnaire was strongly related to the variations of training and performance (r > 0.70). Correlations were lower with the hormonal ratio and insignificant with the heart rate variability.Conclusion. – The questionnaire and the hormonal ratio were good markers of the variations of training and performance contrary to the heart rate variability. 相似文献
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Purpose. – Doping with EPO increases both hematocrit and performance. On the opposite, training reduces hematocrit due to plasma volume extension and overtraining both increases hematocrit and decreases performance. This apparent paradox seems to be explained by a new concept proposed interpreting the interactions between viscosity factors and blood flow.Facts. – Viscosity factors exert a non linear “all or none” effect that can be described according to the “ percolation theory”. Blood viscosity has no hemodynamic relevance by its own, but viscosity factors (hematocrit, red cell deformability and aggregability, plasma viscosity) can result according to flow conditions in self-potentiating phenomena of quick transition between a state of high fluidity and a state of red cell aggregate clumping. In muscle, this model predicts that: (a) during exercise the only viscosity factor that could influence flow is plasma viscosity; (b) at rest all viscosity factors (including high hematocrit) may induce a self-potentiating “viscidation” process.Conclusion. – According to these concepts, supraphysiologic hematocrit values are probably unable to disturb muscular perfusion at exercise, but are likely to promote self-potentiated stasis at rest and thus to increase the risk of thrombosis. 相似文献
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I. Aloulou J. Manetta M. Dumortier F. Brandou E. Varlet-Marie C. Fdou J. Mercier J. -F. Brun 《Science & Sports》2003,18(6):305-307
Objective. – To confirm the assumption whereby overtraining would have opposite effects on the utilisation of the substrates and the somatotropic function.Exposed facts. – The drive has different effects according to its characteristics and its level. It seems y to have two types of drive: that which amplify the aptitude to oxidize lipids (low powers) and that which accroit the aptitude to oxidize glucides (high powers and/or intermittent exercise). Overtraining reverses these two effects. The somatotropic axis has an evolution parallel with these processes and seems implied in those.Conclusion. – This diagram deserves to be confirmed by additional studies. 相似文献
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Aims – Determine the corticotropic responses to acute stress with or without prior exercise training and following the corticotropic phenotype of the rats.Methods and results – Lewis and SHR strains were selected for their opposite corticotropic responsiveness characteristics (high and low in SHR and Lewis strain, respectively). This study shows that exercise training induces opposite adrenal responses in SHR strain and in Lewis strain (which decrease increase its corticosterone concentration, respectively).Conclusion – This suggests that genetic may play an key role in pituitary-adrenal adaptations to exercise training. 相似文献
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Aim – Heart rate comparative study by spectral analysis between a 6 minutes judo randori et a 4 minutes ergocycle exercise at
.Materials and methods – By ten male judokas, both time series were analyzed by short term Fourier transform (time/frequency analysis). Each 512 RR time series drawn from ECG was subdivided by Hanning windowing in 13 samples of 128 values (32 RR periods step). For each sample, both exercise types, means of the ten spectrograms have been computed, yielding two mean spectrograms for each sample.Results – 1) Despite a near maximal heart rate (HR) level between the two exercise types, the spectral energy computed from judo randori was significantly more important than ergocycle spectral energy. This phenomenon yields a qualitative effect of the exercise type (judo or ergocycle) on HRV. 2) the normalized spectral powers of low frequency and high frequency bands respectively, were not significantly different between both exercise types.Conclusion – The autonomie nervous control on HR would depend rather on exercise load than on exercise type. 相似文献