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.     

Dopage et sport : connaissances et attitudes des pharmaciens de la ville de Yaoundé

Introduction – Fourty-one retail pharmacists (23 females and 18 males) out of 70 that Yaoundé town counts, participated to this study aimed at determining their attitudes towards and knowledge in doping. They answered a questionnaire concerning their knowledge of doping agents, how they face doping and the role of pharmacists in doping prevention.Synthesis – Results suggest that pharmacists (54%) have been confronted to doping, less than once a month for 27% of them and at least once a month for the rest. Six pharmacists (15%) have been offered to provide doping agents to sport men. 51% (mainly females) consider that the use of food supplements could induce consumption of forbidden drugs. The majority (83%) of pharmacists (mainly females) consider that doping is a public health problem. They agree (88%) that pharmacists have a part to play in doping prevention but also agree (58%; mainly females) that they are poorly or very poorly informed to that effect.Conclusion – The requests made to pharmacists suggest the consumption of doping agents by sport men in our region. It is therefore necessary to carry out an epidemiologic study on prevalence and consumption patterns.     

Médicaments et performance de la fonction d'équilibration

Introduction – Balance control in some sports discipline can be the aim of the action, and its breaking off can expose to severe trauma.Synthesis of facts – Some drugs' adverse effects can induce lower equilibrium performance, in relation for example with vigilance drop or vestibular ototoxicity. The drug effect site can concern one or more links in the chain (peripheral or central impact). Individual sensitivity is variable, as well as speed of reversibility.Conclusion – Symptoms induced by pathology for which therapy is prescribed are sometimes difficult to distinguish from those induced by therapy itself.     

Comparaison de performances aérobies et anaérobies au cours d'exercices locaux et généraux

Purpose – The relationships between the aerobic and anaerobic abilities for local and general exercises has been studied in twenty three subjects.Methods – Maximal aerobic power (PMA), the lactate level corresponding to 4 mmol l⁻¹ (Pla4) and maximal anaerobic power on a Monark cycle ergometer (general exercises) have been correlated with aerobic and anaerobic performances for knee extension exercises (local exercises). Maximal anaerobic power (Pmax) has been determined by means of a force–velocity test on the same Monark ergometer. Two indices of local aerobic ability were estimated: 1) the peak power (Ppic) measured at the end of an incremental knee extension exercise, 2) the knee extension critical power (PC) calculated as equal to the slope of the relationship between exhaustion time and total work performed during three exhaustives exercises at constant load. Maximal anaerobic power of the knee extensors was determined by measuring the maximal power at an angular velocitie of 240° s⁻¹ (Pbiodex) with an isokinetic ergometer.Results – The correlations between all the indices of local and general aerobic abilities were highly significant (0.82<r<0.96; p<0.001) whatever the expression of the data (absolute values or related to the quadriceps muscle mass). The relationship between PC and Pla4 was significant even when these variables were expressed as fractions of the maximal aerobic power (PC/Ppic and Pla4%: r=0.75; p<0.001). Similarly, Pmax and Pbiodex were correlated even when related to quadriceps muscle mass (r=0.60; p<0.01). In contrast to Pmax, Pbiodex was negatively correlated with the local and general aerobic indices, but only when these variables was related to quadriceps muscle mass (0.44<r<0.63; p<0.05).Conclusions – The general aerobic abilities are very well correlated with the local aerobic abilities. Moreover, the correlation between PC/Ppic and Pla4% suggests that local and the general endurances are partially linked. The best indices of maximal anaerobic power and local anaerobic power are observed in the same subjects. In contrast, the best local and general aerobic indices are observed in the subjects presenting the weakest indices of anaerobic power.     

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.     

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.     

Réponses du cortisol et de la testostérone salivaires au cours de la récupération post-compétitive en rugby

Aim. – In order to evaluate the biological repercussions of the post-competitive tiredness state, we measured the progress of the salivary cortisol and testosterone levels in the players of a rugby-team during the week following an international match.Results. – The results reveal a fall of the cortisol levels during the first 4 days following the competition, compared to the values measured at the same hour of a resting day. Conversely, the testosterone levels present an increase during the same period. Consequently, 5 days of recovery are needed for these two biological variables chosen as tiredness markers to return to their basic values.