Comparaison des données bioénergétiques observées lors d''un exercice musculaire sur bicyclettes équipées de plateaux rond ou «Harmonic

Introduction

In order to “harmonise” the constraints of pedalling (attenuate top dead centre and bottom dead centre), a non circular chain ring called “Harmonic” has been put on the market. The purpose of this study is to understand bioenergetic repercussions of this type of non circular chain ring during muscular exercise upon a bicycle.

Method

Thirteen regional level cyclists took part in this study. Each subject performed two maximal oxygen uptake exercise tests, one with a circular chain ring, the other with a “Harmonic” chain ring with the same cogwheel (52 tooth). They were performed on a cyclo-simulator. Speeds (km·h^t-1) and/or simulated slopes (%) increased every 2 min 30 s. They were, respectively: 28-2, 30-2, 35-2, 37.5-2, 40-2, 40-3, 42.5-3. O₂ uptake (VO₂), pulmonary ventilation and heart rate were measured continuously; and blood lactate concentration was measured during the last 30 s of each level.

Results

Regardless of speeds and slopes, there was no significant difference for VO₂, pulmonary ventilation, heart rate and blood lactate concentration between the two chain rings.

Conclusion

If the chain ring in question is supposed to attenuate top dead centre and bottom dead centre pedalling, it does not present any lessened energy expenditure during muscular exercise.     

Ginseng et exercice supramaximal

Chronic ginseng intake did not appear to improve performance during supramaximal exercise. In the same way, the blood parameters analysed (lactate and testosterone) were not modified by ginseng vs placebo neither at rest or at exhaustion.     

Effet de l'entraînement sur l'anabolisme musculaire : analyse de la réceptivité à la testostérone

This study analysed consequences of testosteronemia changes on anabolic process after endurance physical training. During 8 weeks, rats were physically trained in endurance tests. Plasmatic testosterone concentrations were significantly decreased (P < 0.05), weight of three skeletal muscles (soleus, EDL, tibialis anterior) and total muscular protein concentrations were significantly increased (P < 0.05). After endurance physical training muscular hypertrophy was well evidenced (P < 0.05). The analyse of testosterone muscular receptor was performed, permitting two essentials conclusions: according to fibre histological profiles, hormonal receptivity was more profound on fast-twitch muscles (P < 0.05); this hormonal receptivity persists as well as testosteronemia, which was significantly diminished with endurance training.     

Cortisol, testostérone et rapport testostérone/cortisol au cours d''un trimestre scolaire chez des lutteurs de haut niveau comparés à des étudiants non sportifs

This study presents the saliva cortisol and testosterone levels in young high level wrestlers compared to those of students not involved in sporting activities. Measures were realised during the first school term (September to mid-December) at 3-week intervals. Hormonal levels revealed a higher degree of tiredness in sportsmen than in non-sportsmen. It also appeared that a 2-week resting period (All-Saint's Day at the end of October) permitted return to hormonal reference values at the beginning of the school year.     

Blessures musculotendineuses à répétition survenant sur un terrain métabolique perturbé : à propos d'une observation de maladie de Gilbert chez un sprinter de niveau national

Gilbert's disease is a constitutional disorder of bilirubin glycosilation in the liver. Physical exercise increases free bilirubin in blood, and the disturbance of the liver's metabolic activity could be the origin of muscular and tendon injuries. The diagnosis of Gilbert's disease is made through biological tests, which are necessary as prevention can obviate critical situations. Other metabolic constitutional disorders could be responsible for similar situations, therefore in cases of frequent muscular and tendon injuries, accurate biological investigations must be made.     

Influence d’une compétition de rugby sur le taux de cortisol salivaireInfluence of an international rugby mah upon the concentration of salivary cortisol

Introduction – Measure the influence of a sporting event (in this case an international rugby match) upon the concentration of salivary cortisol.Synthesis of facts – In order to take our study to a successful conclusion, we took salivary samples from the players during the event as well as at the time of a rest day. These concentrations are measured thanks to a radio immunoassay technique. The sporting event  has resulted in a 75% cortisol level rise. This increase reflects both a physiological and a psychological response to a stressful stimulation. The value of the cortisol before the event is also higher (85%) than the one measured at the same time of day during the rest day.Conclusion – This result shows that the sporting event has a positive correlation with the level of the salivary cortisol that it is to say a cognitive anticipation of the subjects.     

Alimentation calcique et effet de l'entraînement physique sur l'os

Physical exercise is able to influence bone structure. In the principal part of cases, physical training results in an enhanced bone density when in any case overtraining could decrease bone density. Numerous factors are involved in the effect of physical training on bone, dietary calcium supply being one. Numerous epidemiological surveys have shown that the daily calcium supply in the French population is between 500 and 1,200 mg/24 hours. Thus part of the French population is under the recommended intake of 1,000 mg. It was proposed that physical training could improve calorie intake and consequently calcium supply. The main objective of this paper is the relationship between exercise and bone structure: second, literature is used to present the role of dietary calcium on bone structure. Finally, the data of a survey in a French population are used in order to define to what extent calcium dietary supply of different sports groups agree with the dietary recommended allowance. They report that calcium supply is influenced by the type of sport, strength trained atheletes enhance calcium intake while endurance trained atheletes present lower calcium intake.     

Effets du repas précompétitif sur la perception de l'effort et sur la glycémie lors d'un exercice de pédalage

The first purpose of the present study was to investigate the effect of three different preexercise meals on perceived exertion and glycaemia during a one-hour bicycle exercise at 80% VO₂ max. The second purpose of this study was to determine the relationship between glycaemia and perceived exertion. Eight athletes (age: 24.6 ± 2.7 years, weight: 78.0 ±6.8 kg, height: 182.6 ± 9.9 cm) completed three assessment sessions, each being preceeded by one of the following meals, ingested 3 h before exercise: 400 mL of water, 400 mL of water and 75 g of glucose, and 100 mL of water and 375 g of potatoes. The subjects 'perceived exertion were measured at times 6, 15, 30, 45, 60 min and glycaemia at 0, 30, 60 min of the exercise. The results showed that perceived exertion (RPE and ETL) of each meal increased as a function of time (P <- 0.05) whereas glycaemia did not differ except for the glucose meal between 30 min and 1 h(P < 0.02). There was no significant difference in ratings of perceived exertion among any meal whereas glycaemia was different between the three conditions only at the beginning and the middle of the exercises (P < 0.04 and P < 0.02, respectively). Moreover, the vectorial angles between the variables ofperceived exertion and the glycaemia are close to 90 °. These results would suggest that perceived exertion does not seem to be affected by the three preexercise meals used in our study. Perceived exertion is not correlated to glycaemia changes during one-hour high intensity exercise. The results would, therefore, suggest that glycaemia is not a contributor signal of perceived exertion in this study. It seems that physiological factors other than glycaemia may have mediated the perceptual intensity at exhaustion. The respiratory-metabolic signals of exertion which are most pronounced at high relative exercise intensity are suggested to influence the perceptual signal of exertion.     

Fracture de fatigue de l'humérus. À propos de trois cas

Three cases of stress fractures of the humeral shaft are reported. The first, a complete spiroid fracture, was observed after a rope climbing exercise following an intensive training period. The two others, radiologically not so spectacular, occurred during the first weeks of this training. The three fractures represent the three different clinical stages. Intensive training and repetitive stress won over an otherwise wonderfully adapted bone structure. Treatment remains orthopaedic, even in the case of the spiroid fracture, with a perfect functional result.     

Influence de l''âge sur différents facteurs déterminants de la performance sur ergomètre aviron

The aim of the present work was to study the evolution with age of the maximal oxygen uptake (VO_2max) and gross efficiency on rowing ergometer in a population of 29 elite oarsmen (17 adults and 12 youths). Independently of body mass, VO_2max increases until 23 years of age and very slightly afterwards. This evolution might be explained by the increase of the volume and intensity of training once the subjects become adults. Efficiency increases continuously with age and leave opportunities to improve this parameter even in high level oarsmen.     

Comparaison de l'oxydation de glucose, d'un mélange de glucose et de fructose, et de saccharose ingérés en bolus ou en doses fractionnées au cours de l'exercice

The purpose of this study was to compare the oxidation rates ofisocaloric amounts of glucose (G), of a mixture of glucose and fructose (G+F), and of sucrose (S) ingested during prolonged exercise (120 min, 58 % V0₂max). The mode of ingestion, that is in a bolus at the onset of exercise or in fractionated doses during the exercise, was also investigated. Six young male subjects ingested a placebo (P), 100 g of G, 50 g of G + 50 g of F, or 95 g of S (13 % concentration) in fractionated doses during exercise, and 100 g of G and 50 g of G + 50 g of F in a bolus at the beginning of exercise. Blood samples were taken before and during the last minute of exercise period. Ingestion of carbohydrates (CHO) does not influence the blood glucose and insulin levels, but decreases by 50% the response of plasma free fatty acid concentration. During the 120-min exercise period, the amounts of ingested carbohydrates which were oxidized were similar for G (53 ± 5 g), G+F (57 ± 6 g) and S (50 ± 7 g). Exogenous CHO oxidation contributed to increasing the total CHO utilization (from 181 to 200 g/120 min) and to reducing fat oxidation (from 86 to 72 g/120 min). Ingestion of CHO as a bolus at the beginning of exercise does not influence G oxidation (58 ± 6 g) but significantly increased the oxidation of the mixture G+F (67 ± 6), probably by favoring fructose utilization which requires a delay. From a practical viewpoint, these results show that the oxidation of S, which is the most widely available oligosaccharide, is similar to that of G or a mixture of G+F. Moreover, in order to maximize exogenous CHO oxidation during exercise, CHO should be ingested early in the exercise period, and not in fractionated doses throughout the exercise period.     

Étude comparative de l'analyse spectrale de la fréquence cardiaque au cours de l'exercice sur ergocycle et de l'entraînement en judoHeart rate comparative study by spectral analysis between two exercises: ergocycle vs judo randori

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.     

Application des opérateurs logiques (booléens) à la recherche bibliographique sur Internet en médecine du sport

Last year, use of logic operators (boolean system) was rarely possible on Internet, in sport medicine or anywhere. But from the beginning of 1997, many search motors on the Net create this possibility, although still with a certain syntax disparity.     

Adaptations myocardiques chez l'enfant prépubère soumis à un entraînement intensif. Étude comparative entre une population de gymnastes et de nageurs

Introduction. The purpose of the present study was to investigate the cardiac structure and function in prepubertal highly-trained swimmers and gymnasts. Method. Thirty-five children (10–11 years) were investigated: nine swimmers (S), 15 gymnasts (G) and 11 as a control group (C). The swimmers and gymnasts had trained on average 10 to 12 h/wk for at least 2 years. The subjects were examined at rest by M-mode, bi-dimensional and Doppler analyses according to standard procedures recommended by the American Society of Echocardiography. The following parameters were obtained: left ventricular (LV) internal dimension at end-diastole (LVIDd) and at end-systole —posterior wall and interventricular septal thicknesses -Left ventricular mass (Lvmass) — LV shortening fraction — ejection fraction — peak velocity of early diastolic rapid inflow and of atrial contraction filling — mitral acceleration and deceleration — isovolumic relaxation time. In addition, the cardiac output was evaluated from transaortic Doppler examinations. The heart rate (Hr) was measured simultaneously with all echocardiographic examinations. Results.- The main results show that LV internal diastolic dimensions and LV mass were significantly higher in S than in the other two groups. No differences were however observed between groups regarding cardiac wall thicknesses. Moreover, all values of G were very close to those obtained by C. Both systolic and diastolic functions were normal in the three groups. Finally, the stroke volume (SV) was higher in S than in the other two groups and because of a bradycardia observed among S, the resting cardiac output was similar in the three groups. The higher LVIDd in S still persisted after correction for Hr. A low diastolic period associated with higher LVIDs can probably explain the high SV in S. Conclusion.- Our results strongly suggest that cardiac structure and function adaptations can occur in prepubertal children as a result of an intensive training program prolonged over a long-term period, only if this program is predominantly based on aerobic exercises. Whatever the kind of sport, neither LV systolic nor diastolic functions are affected by training during prepuberty. Further investigations will however be needed in order to better understand diastolic function adaptations to intensive aerobic training in children.     

Évolution des erreurs techniques et de quelques variables physiologiques pendant la course d'orientation

During orienteering, the accumulation of technical errors (TE) can be an important factor of handicap at the arrival. In the same conditions of championships, ten voluntary national runners (age: 29.2 ± 3 years, height: 176.8 ± 3.5 cm, body mass: 65.0 ±6.8) participed to the study. Firstly in laboratory the subjects performed a treadmill test in order to study their physical capacity (aerobic fitness and oxygen consumption). The initial speed (12 km·h⁻¹) increased by 1 km·h⁻¹ every 4 minutes. During the last minute of each step a blood sample (50 μl) was taken on a finger for lactate analyze (Kontron). Two days later the subjects participed in an orienteering race (OR) of four loops (Bi₁, B₂, B₃, B₄) stepping in a central point; the first and third loops (B₁, B3) were technical orienteering while the second and the fourth (B₂, B₄) were rough orienteering. During the race the heart rate (HR) was recorded by means of a Sport Tester PE 4 000. The nature, the number and the moment of TE were determined with the help of the map area of each subject and time keeping. During OR the subject's physical capacity (running speed, HR, lactates, carbohydrate) was evaluated when the runners arrived at the crossing point of the loops. The results give some evidence that the anaerobic threshold quickly is reached during technical orienteering (B₁) and stay at a level hihger than 4 mmoles.l⁻¹ during the whole field test, suggesting that the energy expenditure was very high. It is difficult to compare the physical capacity and the psychological behavior of the subjects during OR yet two distinctive critical pediods have been observed for TE in OR (B₃, B₄); nevertheless our study confirms that the number of TE (which is a picture of the mental performance) is linked to the decrease of the physical capacity. Indeed the increase of HR (HRmax-HRmin) during OR stabilized in the first three loops (B₁, B₂, B₃) at 25 beats, min⁻¹, then the increase of HR was about 31 beats.min⁻¹ in B4. This increase of HR (HRmax-HRmin), is due to the muscular fatigue, the subjects must have some rest and they run slowly because the carbohydrates decrease, excepted for the best runners. Thus the consequences of an insufficient warm-up in the first quarter of the race and/or supply of energetics substrates during the whole OR has been brought to attention.     

Facteurs de la variation de la fréquence cardiaque maximale: hypothèse «enképhalinique

To try to explain the decrease in maximal heart rate under different situations (ie, chronic hypoxia, ageing, proteino-energetic malnutrition), cardiac concentration and flow of leucine-encephalin peptide in isolated and perfused hearts were studied in rats. The heart leucine-encephalin concentration which was 301 ± 60 fmol/g before perfusion, increased up to 543 ± 125 fmol/g after perfusion (1 h). The total release during perfusion was four times the initial concentration. Concerning the antagonism of leucine-encephalin on cardiotropic adrenergic effects on isolated cardiomyocytes, it is possible to propose this mechanism to explain totally or partially the decrease in maximal heart rate under particular situations.