L’étude des forces de réaction au sol peut-elle être un indicateur de la stabilité de la chaussure lors de la locomotion ?

Objective

The aim of this study was to determine the influence of ground reaction forces on the footwear stability.

Material and methods

Twelve healthy men have walked on a treadmill ergometer ADAL with five different shoe models and in a barefoot condition. Here, the shoe called “shoe 1” is known for its capacity to stabilize the foot. Ground reaction forces (F_x, F_y, F_z) were recorded at constant speed (2, 4 and 6 km h⁻¹), and during transition phases (0 to 2, 0 to 4, 0 to 6 km h⁻¹). Two running conditions (8 km h⁻¹ at constant speed and 0 to 8 km h⁻¹ in transition) have completed this protocol. Then, each subject filled in a questionnaire to evaluate, for each shoe, different sensations: stability during walking and running, foot support, heightening of the rearfoot, width of shoe at the heel, general comfort, cushioning. At last, different geometrical parameters of each shoe were measured.

Results and discussion

The results show that, in all tested conditions (constant speed and transition phases, walking and running), medial force peaks are significantly more important in barefoot condition than all shod conditions, except for the shoe 1. As the barefoot condition is, according to the literature, the best condition of stability and as the shoe 1 is known for its capacity to stabilize the foot, these results could suggest that a better stability could be associated with more important medial force peaks.     

Comparaison des paramètres de la relation puissance–temps limite obtenus par différents modèles de la puissance critique

Introduction

The aim of this study was to determine how the choice of the model would affect the estimation of the parameters of the relation between power and limit time.

Synthesis of facts

Twelve volunteers have done five or six time trials on cycle ergometer making it possible to test six models: two linear forms (Lin-W et Lin-P) and one non-linear form (Nlin-2) of the simple hyperbolic model, two models with a finite limit for maximal power (Nlin-3 et EXP) and one model which distinguished the critical power and the maximal aerobic power (Mod-α). Lin-P and EXP have given the highest estimates for the critical power and Nlin-3 the lowest. No statistical difference was observed between the estimates from Lin-W, Nlin-2 and Mod-α.

Conclusion

Although Nlin-2 was better on the statistical ground and Mod-α could give more information on the anaerobic contribution according to the total power, Lin-W would be a robust method to estimate the critical power.     

Extension du modèle puissance–temps limite pour estimer la production d’énergie aérobie et anaérobie lors de l’exercice intense

Aim

Examine how the modelling of the relation between power and time to exhaustion can provide an estimation of the production of aerobic and anaerobic energy during intense exercise.

Current knowledge

The hyperbolic model made it possible to define the critical power corresponding to the maximal rate of energy renewed by aerobic metabolism. A new model distinguishing the critical power from the maximal aerobic power has been built to estimate more precisely the anaerobic contribution. Data from middle distance runners and subjects tested on cycle ergometer showed a relative contribution of anaerobic metabolism arising from critical power and increasing until around 10 % of total power when aerobic energy production reaches its maximum.

Prospects

Considering the slow component of oxygen uptake would provide a more precise analysis of energy production and transformation during exercise at high intensity.     

Quels tests de terrain pour le suivi de la performance athlétique en sport collectif ?

Introduction

To monitor athletic performance throughout a team-sport season, strength and conditioning coaches are used to program various field tests that evaluate physiological variables predictive of performance in their activity. Nevertheless, performing all these field tests is time consuming and not well appropriated for frequent monitoring.

Synthesis of the facts

The present study investigated whether a single test can be used as a surrogate of overall team athletic performance.

Conclusion

It appears that the 30-15 Intermittent Fitness Test and a repeated sprint ability test, but not explosive power of lower limb or sprinting tests, are sensitive enough to differentiate different performance levels throughout the season.     

Effets de la pratique de la gymnastique d’entretien chez des seniors sur la condition physique,la fonction cognitive et la prise médicamenteuse

Objective. – The aim of the study was to investigate the effects of regular gymnastic activity practice on fitness, cognitive function and medication in healthy elderly women.Method. – Twenty-four women were separated into 2 groups, a sedentary group and a gymnastic group. In order to be included in the gymnastic group, women needed to have participated for at least 2 consecutive years in gymnastic sessions for a minimum of 10 months per year. Subjects were on average aged 60.3 ± 1.4 years. All the women filled in clinical and physical activities questionnaires. Then the following tests were taken: Martinet, 6 min walking test, 3 static balance tests and a memory test.Results. – Walking speed (P < 0.01) and distance of walking (P < 0.05) were significantly higher in the gymnastic group in comparison with the sedentary women and the consumption of medicine was significantly lower in active compared with sedentary women (P < 0.05). So, regular gymnastic practice reduces the consumption of medicine and could preserve autonomy by maintening an optimal walking speed, thus decreasing the risk of falls.     

Historia natural de la hernia de disco lumbar. ¿Tiene el realce con gadolinio valor pronóstico?

Objectives

To evaluate the percentage of disc hernias that have disappeared after one year of follow-up and the time to disappearance. To determine whether gadolinium enhancement is useful for predicting whether the hernia will disappear. To analyze whether the pattern of enhancement can help predict whether the fragment will disappear.

Material and methods

This prospective study included 118 patients with acute symptoms of lumbosciatica and a herniated disc diagnosed by CT. In 72 patients, we performed gadolinium-enhanced MRI every 6 months for one year or until the herniation disappeared; we related the findings of protrusion, extrusion, and the enhancement pattern with the disappearance or persistence of herniated disc material. We analyzed the results with univariate and multivariate statistics.

Results

The 59% of the hernias disappeared within 1 year of follow-up and 66% disappeared within the first 8 months of follow-up. The 83% of the extruded hernias disappeared, and this was significant in the multivariate analysis (P<.005). The absence of enhancement was significantly associated with the persistence of the hernia in the univariate analysis. The enhancement pattern was not useful for predicting whether the hernia would disappear. Five hernias disappeared within the first two months.

Conclusions

A high percentage of disc hernias disappear. We found a significant association between extrusion and disappearance but no correlation between the pattern of gadolinium uptake and the disappearance of the hernia.     

Resonancia magnética de perfusión en astrocitomas de alto grado: el volumen sanguíneo cerebral,la altura del pico y el porcentaje de recuperación de intensidad de señal ¿pueden discriminar entre progresión y seudoprogresión?

Objectives

To study the usefulness of common MRI perfusion parameters for identifying pseudoprogression in high grade astrocytomas.

Material and methods

This retrospective case-control study compared the relative cerebral blood volume (rCBV), the relative percentage of signal intensity recovery (rPSR), and the relative peak height (rPH) recorded in a sample of 17 cases of anaplastic astrocytomas and gliomas considered to be undergoing pseudoprogression by biopsy or follow-up with those recorded in a sample of histologically similar tumors that were treated and considered to be undergoing progression by histologic study or follow-up. We evaluated the accuracy of these parameters and the correlations among them. Statistical significance was set at P<.05.

Results

The rCBV, rPSR, and rPH were significantly different between the two groups (P=.001). The cutoff values rPH=1.37, rCBV=0.9, and rPSR=99% yielded sensitivity (S)=88% and specificity (Sp)=82.2% for rPH, S=100% and Sp=100% for rCBV, and S=100% and Sp=70.6% for rPSR, respectively. We found negative correlations between rPRS and rPH (−0.76) and between rPRS and rCBV (−0.81) and a high positive correlation between rPH and rCBV (0.87).

Conclusion

The variables rPH and rCBV were useful for differentiating between pseudoprogression and true progression in our sample. The variable rPRS was also very sensitive, although the overlap in the values between samples make it less useful a priori.     

Utilidad de la ecografía intestinal en la enfermedad inflamatoria intestinal

Imaging techniques play a fundamental role in the initial diagnosis and follow-up of inflammatory bowel disease. Intestinal ultrasound has high sensitivity and specificity in patients with suspected Crohn's disease and in the detection of inflammatory activity. This technique enables the early diagnosis of intra-abdominal complications such as stenosis, fistulas, and abscesses. It has also proven useful in monitoring the response to treatment and in detecting postsurgical recurrence. Technical improvements in ultrasound scanners, technological advances such as ultrasound contrast agents and elastography, and above all increased experience have increased the role of ultrasound in the evaluation of the gastrointestinal tract. The features that make ultrasound especially attractive include its wide availability, its noninvasiveness and lack of ionizing radiation, its low cost, and its good reproducibility, which is important because it is easy to repeat the study and the study is well tolerated during follow-up. This review summarizes the role of intestinal ultrasound in the detection and follow-up of inflammatory bowel disease.     

Facteurs limitants de la performance en haute altitude : opération Everest III,Comex'97

Objectives – Operation Everest III (Comex'97) was performed to evaluate the physiological, psychological and pathological mechanisms induced by a prolonged exposure to extreme altitude, up to 8,848 m (altitude of Mount Everest).Methods – Eight male subjects (23 to 37 years old) have been studied in normoxia, then, after 6 d of acclimatization at 4350 m, in a hypobaric chamber (Comex SA, Marseille) where they stayed 31 d, from 5000 m to 8848 m of simulated altitude. Eighteen protocols, from 14 scientific teams, have explored various aspects of acclimatization to extreme altitude.Results – The decrease in plasma volume is one of the factors involved in the reduction of physical performance, as witnessed by the 9% increase in VO_2max at 6000 m under infusion of 300 ml hydroxyethylamidon. Ventilatory and cardiac responses to hypoxia at exercise have an opposite trend, with an increase in ventilatory and a decrease in cardiac response. Autoregulation of cerebral circulation is altered above 7000 m. Left ventricular function is maintained up to 8000 m, in spite of an important increase in pulmonary artery pressure. Ventricular relaxation is altered, probably because of altered ventricular filling. The decrease in food intake contributes to the loss of body weight (mean of 5.4 kg). Nutritional habits are modified, with shorter and more frequent meals and a decreased interest for food. Lipolysis in fat tissue is blunted, suggesting, like for cardiac adrenergic receptors, a desensitization linked to a change in G proteins. Few psychological alterations were observed below 6500 m. However, changes in mood state and a high level of anxiety have been noticed and correlated to other physiological or psychometric parameters.Conclusion – Human body is able to develop adequate responsive mechanisms to oppose the severe hypoxia (mean arterial PO₂ of 30.6 mmHg at 8,848 m). Mental capacities are also slightly diminished, but only above 6500 m.     

Effet de la course d’endurance et/ou des isoflavones sur la masse osseuse de la rate castrée

Aim – To study the effects of endurance running (15 m/min during 20 min/day to 28 m/min during 1 h/d, 6 days/week during 12 weeks, corresponding to 62% of the VO₂ max of the animals) or of a treatment by isoflavones (Soylife 100 : 400 μg j^–1 g^–1 of body weight during 12 weeks), either only or cumulated with running, on the osteopenia induced by castration in adult female rat.Results and discussion – Each one of these two treatment has a protective effect of the bone mineral density at the femoral total, diaphysaire and metaphysaire level. But contrary to what had been reported on the cumulated effects of long term endurance running and of a 17β-estradiol treatment 〚3〛, we did not note any additive effect of these two treatments.