François Trudeau

Contribution of school programmes to physical activity levels and attitudes in children and adults.

AbstractAlthough children and youth currently form the most active segments of the population in developed societies, there is a marked trend toward an increase in sedentary lifestyle among school-age children. The purpose of this review is to analyse the effects of school physical education (PE) programmes on: (i) the physical activity (PA) levels of participants as children and adults; and (ii) attitudes toward PE and PA in the same groups. Based on the literature analysed, it can be suggested that a sufficient quantity of a quality PE programme can contribute significantly to the overall amount of moderate-to-intense PA of the school-age child. Schools also have the potential to influence the habitual PA of children by encouraging increased participation in extracurricular sports activities, by favouring active commuting to school and by providing exercise equipment and supervision for youth in their neighbourhoods. Most young children have a very positive attitude towards PE. However, as they grow older, their perception of PE as a positive experience seems to become more ambiguous. From the few studies available, it seems likely that quality PE programmes help to maintain initial positive perceptions. Future research should address factors influencing the change of perceptions as a child matures. In addition to offering a quality PE programme, schools should ensure that the total weekly amount of PE is sufficient not only to maintain but also to enhance a child’s physical fitness. More research is needed to determine the ability of school PE programmes to influence PA behaviour in adult life and to evaluate strategies that will make optimal use of the curricular time allocated to PE.

Impaired modulation of AMPA receptors by calcium-dependent processes in streptozotocin-induced diabetic rats.

The mechanisms by which diabetes impairs cognitive function are not well-established. In the present study, we determined the electrophysiological and biochemical nature of disturbances in the mechanism of long-term potentiation (LTP) in diabetic rats. As previously reported, the administration of streptozotocin (STZ) was found to reduce the magnitude of LTP in the CA1 region of the hippocampus, while the same treatment did not interact with the capacity of the hippocampus to generate long-term depression induced by low-frequency stimulation. In addition, STZ treatment did not modify the component of excitatory postsynaptic potentials mediated by activation of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors, suggesting that NMDA receptor function remained intact in STZ-treated slices. At the biochemical level, the capacity of calcium to increase [3H](RS)-alpha-amino-3-hydroxy-5-methylisoxazole propionic acid (3H-AMPA) binding to glutamate/AMPA receptors in rat brain tissue sections was markedly affected in most regions of the hippocampus of STZ-treated rats. Moreover, changes in 3H-AMPA binding properties elicited by both exogenous phospholipase A2 and melittin, a potent activator of endogenous phospholipases, were also altered in synaptoneurosomes from diabetic rats. Taken together, the present data suggest that the loss of LTP maintenance in STZ-treated rats is more likely the result of disruption of calcium-dependent processes that are suspected to modulate postsynaptic AMPA receptors during synaptic potentiation. Understanding the biochemical factors participating in the impairment of AMPA receptor modulation might provide important clues revealing the very basis of memory deficits in diabetes.

Relationships of Physical Activity to Brain Health and the Academic Performance of Schoolchildren

This review examines possible relationships between academic performance and participation in sports, physical education, and other forms of physical activity. Recent fundamental research has reignited interest in the effects of physical activity on cognitive processes. Experimental studies of potential mediating variables point to physiological influences such as greater arousal and an increased secretion of neurotrophins and psychosocial influences such as increased self-esteem and connectedness to schools. In the specific case of sports, experimental studies are limited to demonstrations of greater attention and acute gains of mental performance immediately following such activity. Several quasi-experimental studies of other types of physical activity have been completed, mainly in primary school students; these have found no decrease in academic performance despite a curtailing of the time allocated to the teaching of academic subjects. Indeed, in some cases, experimental students undertaking more physical activity have out-performed control students. Many investigators have looked at cross-sectional associations between participation in sport or other forms of physical activity and academic performance. Despite difficulties in allowing for confounding variables, particularly socioeconomic status, the overall conclusion has been of a weak positive association. From the practical point of view, it can be concluded that the physical activity needed for healthy child development can be incorporated into the school curriculum without detriment to academic achievement.

Binding Properties of Glutamate Receptors in Streptozotocin-Induced Diabetes in Rats

The biochemical mechanisms by which diabetes modulates cognitive function are not well established. Here, we determined the effects of streptozotocin (STZ) administration on the binding properties of α-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) subtypes of glutamate receptors in rats, using quantitative autoradiographic analysis of 3H-AMPA and [3H]glutamate binding on brain tissue sections. The STZ injection (70 mg/kg intraperitoneally) produced a reduction of 3H-AMPA binding in various brain regions, an effect that is due to a decrease in receptor affinity. The STZ-induced reduction of 3H-AMPA binding varied in different brain structures, being more pronounced in the striatum, cerebral cortex, and hippocampus and almost absent in the cerebellum. Western blots performed on hippocampal membranes revealed that the decrease in 3H-AMPA binding is possibly associated with changes in immunologic properties for one glutamate receptor subunit (GluRl). Finally, the effect of STZ-induced diabetes appeared to be specific to the AMPA subtype of glutamate receptors, as the same treatment did not modify [3H]glutamate binding to NMDA receptors. These changes in AMPA receptor properties may have important implications for understanding the biochemical mechanisms underlying cognitive impairment in diabetes.

Up-regulation of glutamate receptors is associated with LTP defects in the early stages of diabetes mellitus

AbstractAims/hypothesis. Recent studies involving electrophysiology and immunolabelling indicate that short-term insulin treatment of hippocampal neurons in culture induces changes in glutamate receptor function, suggesting that this receptor system can be altered on a relatively rapid time scale during diabetic conditions. To investigate this hypothesis, we examined whether brain glutamate receptors and long-term potentiation are altered in the early stages of diabetes mellitus in non-obese diabetic mice, a genetic model of Type I (insulin-dependent) diabetes mellitus. Methods. In vitro receptor autoradiography and immunoblotting were used to study the impact of diabetes on brain glutamate receptors. From an electrophysiological point of view, field potential recordings were also examined in area CA1 of hippocampal slices to determine the influence of diabetes on long-term potentiation. Results. Quantitative autoradiographic analysis revealed enhanced 3H-glutamate binding to several brain regions of diabetes mice, with maximal increases in the cerebral cortex and hippocampus. Saturation kinetics within the cerebral cortex disclosed that this change of 3H-glutamate was possibly due to an increase in the maximal number of N-methyl-D-aspartate binding sites, an interpretation that was corroborated by Western blot analysis of N-methyl-D-aspartate 2A subunits. Impairment in the expression of hippocampal long-term potentiation was also observed in diabetic mice, while the failure to elicit synaptic potentiation was prevented by insulin treatment. Conclusion/interpretation. Because glutamate receptors are thought to be involved in several degenerative processes, our results suggest that up-regulation of these receptors in the early stages of diabetes could represent an important mechanism underlying neurological complications within the brain of diabetic patients.

Preserved LTP and water maze learning in hyperglycaemic-hyperinsulinemic ZDF rats

Previous investigations have demonstrated that cognitive deficits as well as hippocampal dysfunctions are generated in animals presenting manifestations of Type 1 diabetes (T1D) mellitus. The present study examined whether such deficits can also be reproduced in the Zucker Diabetic Fatty (ZDF) rats after they developed symptoms of Type 2 diabetes (T2D). Learning and memory assessments were performed using the Morris water maze 5 weeks after the animals presented symptoms of Type 1 diabetes for Experiment 1 (Exp 1) and after 8 weeks for Experiment 2 (Exp 2). Testing in the water maze revealed that ZDF rats learned the task normally, although control rats were found to swim significantly faster after 5 or 8 weeks of untreated diabetes. From an electrophysiological perspective, we observed that the integrity of synaptic function was also preserved in ZDF rats as no alterations in long-term potentiation (LTP) were observed in the area CA1 of hippocampal slices. It is concluded that hyperglycaemia is not the only factor influencing water maze learning and LTP in this animal model of Type 2 diabetes (T2D). The experiments suggest that the resistance of ZDF rats to cognitive and electrophysiological dysfunctions might be related to the protective action of hyperinsulinemia. Indeed, measurements of the plasma insulin level at the end of testing were significantly superior in ZDF rats in comparison to control rats.

Is there a Long-Term Health Legacy of Required Physical Education?

This article documents current literature on the potential long-term effects of school physical education on various outcomes in adults. A first observation is the rarity of publications on this topic. Nevertheless, the available literature suggests that physical education should offer a variety of either lifelong physical activities or sports in order to reach children with differing interests. In some children, competitive sports may generate a lifelong interest in physical activity, but most children may be better socialized by lifelong physical activities. In order to expose children to such a wide choice of physical activities, more time should be allocated to physical education instruction. Substantial further research is needed to increase our understanding of the long-term impact of school physical education programmes.

Follow-up of participants in the Trois-Rivières Growth and Development Study: Examining their health-related fitness and risk factors as adults

The purpose of the study was to examine the effect of daily physical education in primary school on some indices of fitness (PWC170/kg, handgrip strength, sit and reach flexibility, abdominal muscle endurance, and balance), cardiovascular health (lipid profile, waist‐to‐hip ratio), and anthropometry in the adult years. Four subsamples of participants in the Trois‐Rivières Growth and Development Study were examined: experimental men (n = 32), experimental women (n = 36), control men (n = 30), and control women (n = 35), some 20 years after completion of primary school. During 6 years of primary school education, the experimental group received 5 h of physical education each week, whereas the control group received only the typical Provincial program of a single 40‐min period per week. Experimental men and women showed a significant advantage over their respective control groups on the Flamingo balance test, but scores for the remaining physical and health‐related fitness tests (PWC170, handgrip strength, total cholesterol, LDL‐C, HDL‐C, Apo B, triglycerides, blood pressures, waist‐to‐hip ratio and percentage of body fat) did not differ between experimental and control subjects. It is concluded that participants in a daily physical education program during primary school do not display any advantage of physical fitness over control subjects as adults. This underlines the necessity of stimulating physical functions throughout the lifespan in order to maintain physical fitness. However, the better result of experimental subjects on the balance test suggests, perhaps, that the school physical education program may have had a more permanent effect on some components of motor skills. Am. J. Hum. Biol. 12:207–213, 2000.

Resetting of the cardiopulmonary baroreflex 10 years after surgical repair of coarctation of the aorta

OBJECTIVE To characterise cardiopulmonary baroreflex responses and examine the effects of a 45 minute cycling bout late after successful repair of coarctation of the aorta. SUBJECTS 10 young adults (mean (SEM) age 18.1 (2.6 years)) operated on for coarctation of the aorta 12.7 (3.5) years earlier, and 10 healthy controls. DESIGN Forearm blood flow (venous occlusion plethysmography) and vascular resistance, left ventricular internal diastolic diameter, and central venous pressure estimated from an antecubital vein were measured in the supine position at baseline and during five minute applications of lower body negative pressure (LBNP) at −15 mm Hg (LBNP−15) and −40 mm Hg (LBNP−40). Venous samples were obtained at baseline and during LBNP−40 for noradrenaline (norepinephrine), adrenaline (epinephrine), renin activity, and aldosterone. The tests were repeated after 45 minutes of moderate exercise. RESULTS Baseline heart rate (78 (9)v 64 (6) beats/min), echocardiographic cardiac output (6.9 (1.1) v 5.0 (0.2) l/min), shortening fraction (41.7 (1.8)% v 33.3 (1.3)%), and forearm blood flow (3.4 (0.4) v2.3 (0.3) ml/100 g/min) were higher in the coarctation group than in the controls (p < 0.05). Changes in forearm blood flow and forearm vascular resistance from baseline to LBNP−40 were similar in both groups, but the relation between forearm vascular resistance and estimated central venous pressure or left ventricular internal diastolic diameter was shifted downward in the coarctation group. Plasma adrenaline was increased in the coarctation group (baseline: 3.2 (0.6) v 2.4 (0.3) pmol/l in controls; LBNP−40: 687 (151) v 332 (42) pmol/l) (p < 0.05). Both groups showed a similar downward displacement of forearm vascular resistance (p < 0.05) after exercise. CONCLUSIONS There appears to be resetting of the cardiopulmonary baroreflex to a lower forearm vascular resistance in young adults operated on for coarctation of the aorta, associated with hyperdynamic left ventricular function. Raised circulating adrenaline could contribute to the lower forearm vascular resistance.

Effects of dominant somatotype on aerobic capacity trainability

Purpose: This study examined the association between dominant somatotype and the effect on aerobic capacity variables of individualised aerobic interval training. Methods: Forty one white North African subjects (age 21.4±1.3 years; V˙o2max = 52.8±5.7 ml kg−1 min−1) performed three exercise tests 1 week apart (i) an incremental test on a cycle ergometer to determine V˙o2max and V˙o2 at the second ventilatory threshold (VT2); (ii) a VAM-EVAL track test to determine maximal aerobic speed (vV˙o2max); and (iii) an exhaustive constant velocity test to determine time limit performed at 100% vV˙o2max (tlim100). Subjects were divided into four somatometric groups: endomorphs-mesomorphs (Endo-meso; n = 9), mesomorphs (Meso; n = 11), mesomorphs-ectomorphs (Meso-ecto; n = 12), and ectomorphs (Ecto; n = 9). Subjects followed a 12 week training program (two sessions/week). Each endurance training session consisted of the maximal number of successive fractions for each subject. Each fraction consisted of one period of exercise at 100% of vV˙o2max and one of active recovery at 60% of vV˙o2max. The duration of each period was equal to half the individual tlim100 duration (153.6±39.7 s). After the training program, all subjects were re-evaluated for comparison with pre-test results. Results: Pre- and post-training data were grouped by dominant somatotype. Two way ANOVA revealed significant somatotype-aerobic training interaction effects (p<0.001) for improvements in vV˙o2max, V˙o2max expressed classically and according to allometric scaling, and V˙o2 at VT2. There were significant differences among groups post-training: the Meso-ecto and the Meso groups showed the greatest improvements in aerobic capacity. Conclusion: The significant somatotype-aerobic training interaction suggests different trainability with intermittent and individualised aerobic training according to somatotype.