Facteurs de risque,lipoprotéines et activité physique et sportive

Aim. – Estimate the impact of physical activity on cardiovascular risks factors.Recent data. – Coronary artery atherosclerosis is a multifactorial disease with a progressive evolution. Physical exercise has an impact on a majority of classical coronary artery disease risk factors. However, in daily practice, it is difficult to assess nutritional behaviours or the physical activity level. Only a very meticulous evaluation would enable the study of their actual and specific impact. Lipoprotein metabolism is dynamic and the effects of prolonged physical activities remain complex. The impact on low-density (LDL) lipoproteins is generally weak, whereas it is highly significant on triglycerides and on high-density lipoprotein (HDL) cholesterol. Generally, the beginning of a prolonged physical exercise induces an increase in HDL cholesterol between 0.02 and 0.08 g/l and a decrease of triglycerides between 0.05 and 0.38 g/l.Conclusion. – To obtain such a result, prolonged but not necessarily very intense physical exercise is necessary to consume 1200–2200 kcal per week. The promotion of physical exercise should be the cornerstone of coronary artery disease prevention.     

Les bases génétiques et moléculaires de la performance et de l'adaptation à l'exercice physique

Objectives – This paper reviews the state of our knowledge on the genetic and molecular bases of performance and the response to exercise training, the theme of the inaugural conference of the XIXth annual meeting of the Société Française de Médecine du Sport held in Rennes in October 1999.Topics – The studies on the genetic bases of performance performed over the past 20 years suggest that 25 to 50% of interindividual differences observed in maximal and sub-maximal oxygen consumption as well as in other indicators of aerobic performance could be explained by genetic factors. For metabolic and histochemical properties of skeletal muscle, heritabilities ranging from 40 to 70% have been reported. Considerable interindividual differences are also observed in the cardiorespiratory, metabolic and morphologic adaptations to exercise training and results from twin and family studies suggest that these differences are also determined by genetic factors. Unlike many other complex traits such as hypertension or obesity, the search for candidate genes of performance is in its infancy. Only a few studies with candidate genes such as the angiotensin converting enzyme (ACE), the muscle specific creatine kinase (CKMM) or genes of mitochondrial DNA have reported positive results with indicators of aerobic performance.Conclusion – More studies are needed before any conclusion could be made about the role of these genes in performance and adaptation to exercise training. Although the molecular dissection of performance and adaptation to regular exercise is a complex task, considerable progress will probably be achieved in the next decade in our understanding of the molecular basis of these complex phenotypes.     

Cinétique du cortisol et de l'hormone de croissance plasmatiques lors de deux épreuves sous-maximales avec et sans récupération

Introduction – The purpose of this study is to evaluate cortisol and growth hormone kinetics in plasma during a sub-maximal exercise with and without recovery.Results – There is a significant difference of cortisol and growth hormone kinetics between the two tests. The cortisol concentration increased significantly during exercise without recovery period, the changes of plasmatic cortisol were not significant during exercise with recovery. Plasmatic growth hormone increases after exercise without recovery.Conclusion – The absence of recovery period contributes to increase considerably the level of cortisol and growth hormone in plasma and decreases probably anabolic process in post exercise period.     

Caractéristiques physiques et physiologiques de cyclistes professionnels

Introduction. – We aimed to characterize the physical capacities of a population of professional cyclists using anthropometrical, cardiovascular, respiratory, ventilatory, and energetic measures.Synthesis of facts. – Eight professional cyclists participated in this study. They performed over 1 day, 5 exercises (progressive and constant-load test) on a cyclo-ergometer.Conclusions. – Physical and physiological results confirmed previous observations done on professional cyclists. The values of maximal power tolerated and time to exhaustion at this power are reproducible during the day thus demonstrated the excellent capability to recover of the professional cyclists.     

Vertiges,troubles de l'équilibre et sport

Aims – To point out that dizziness can be generated by sport practice, that unrecognized pathologies can provoke dizziness in sportsmen and that dizziness could be prevented by physical activities.Current knowledge – Balance disorders can be related to pathology of one or more afferences (vestibular, visual, somesthetic), a conflict in these afferences usage (motion sickness, Coriolis forces), central integration (vigilance-deficit, drugs, etc.) or motor effector dysfunction (muscular trauma, etc.).Points of views and plans – Sport practice can modify sensory-motor strategies by reinforcing the preferential usage of a given type of information. In elderly, physical activities, by maintaining or increasing the weight of proprioception, diminish dependency to the visual afferent.