Simulation de la fonte printanière au bassin des Eaux Volées, forêt Montmorency, Québec

Les auteurs présentent une étude sur la simulation de la période de fonte de la neige au bassin des Eaux Volées (forêt Montmorency) par le modèle SSARR. Si la reconstitution des débits moyens de la fonte printanière est acceptable, la sous-estimation des débits journaliers de pointe et la fonte rapide des années 1972, 1974, 1976, 1978 et 1980 ont poussé les auteurs à faire l'analyse des composantes hydro-climatiques reliées à ces événements. Cet examen a clairement établi que: 1) dans des conditions de temps relativement dégagé, la méthode de degré-jour utilisée évalue d'une façon acceptable l'écoulement ainsi que les débits de pointe journaliers; 2) Dans des conditions de type de temps cyclonique du sud, les effets combinés de la température et des précipitations accompagnés de flux de chaleur advective transportée par la masse d'air humide expliquent les coefficients de ruissellement élevés, la sous-estimation des débits de pointe et l'apparition des débits extrêmes. L'importance du flux thermique advective a été souligné et discuté.The snowmelt simulation periods in the Eaux Volées watershed are well computed when using the SSARR model, but the daily runoff simulations do not fall within an acceptable range. Analysis of related hydro-climatic components was necessary to explain the underestimates of daily peak flows and early snowmelt for the years 1972,1974,1976,1978 and 1980. The test has clearly established that: 1) under clear sky conditions the daily snowmelt and the peak flow simulations work well when using the degree-day method; 2) under overcast conditions the combined effects of rain, temperature, wind and advected warm air from southern cyclonic conditions account for the underestimated peak flows and the high runoff coefficients. The importance of the advective heat transfer is underlined in relation to flow forecasting

Solution numérique de la captation de gouttes de pluies verglacantes en présence de gravité sur une forme cylindrique

Les gouttes contenues dans les pluies verglaçantes, provoquant le verglas, diffèrent de celles obtenues dans les nuages givrants; leur diamètre est environ 20 fois plus grand. On doit donc tenir compte de la gravité, ce qui n'avait jamais été fait auparavant. Un terme relié à la forme gravitationnelle est ajouté à la force d'inertie et de traînée dans les équations décrivant le mouvement de gouttelettes d'eau dans un courant d'air autour d'un cylindre. La technique des éléments finis est utilisée pour obtenir la solution des équations. A partir des équations différentielles non-linéaires, et en utilisant la méthode de Newton-Raphson pour la solution de ces équations, les résultats donnent les vitesses pour un champ de gouttelettes. La direction à la surface du cylindre de la vitesse de ces gouttelettes, donne le coefficient de captation locale, à partir duquel, le coefficient de captation totale est trouvé en intégrant numériquement. Les résultats du coefficient de captation total pour une vitesse d'eau adimensionnelle influencée par la gravité, semble donner les mêmes résultats que ceux obtenus par McComber et Touzot 1981, sans gravité. Les résultats montrent que, pour les conditions de pluies verglaçantes, le coefficient de captation total varie de 0,97 à 0,99. Les ouvrages montrant la grosseur des gouttes provoquant le verglas sont très rares. Par conséquent, les résultats du diamètre des gouttes originent de la région de Montréal et des environs. Quant à la vitesse du vent, elle est calculée en fonction de la température. Le maillage utilisé ne permet que le calcul du coefficient de captation en amont du cylindre seulement

Outdoor Time is Not Associated with Metabolically Healthy Overweight and Obesity Phenotype in Canadian Children Aged 6-14 Years

International Journal of Exercise Science 13(2): 383-394, 2020. A large proportion of children living with obesity have favorable cardiometabolic profiles despite their adiposity levels, who are referred to as metabolically healthy overweight or obese (MHO). However, the contribution of active outdoor time to the MHO phenotype is unknown. The purposeof this study was to investigate the association between outdoor time and moderate-to-vigorous physical activity (MVPA) with the MHO phenotype. A cross-sectional analysis of overweight/obese children aged 6-14 (n= 386) from the Canadian Health Measures Survey was performed. Outdoor time was self-reported using five questions in relation to the school schedule to produce a computed score ranging from 0-25. MVPA was measured using accelerometers. The MHO phenotype was defined based on the absence of cardiometabolic risk factors: triglycerides, HDL-cholesterol, systolic and diastolic blood pressure, and glucose (MHO: 0 cardiometabolic risk factors). The proportion of children living with obesity with the MHO phenotype was 58.5%. No significant differences were observed between MHO and non-MHO according to outdoor time or MVPA (p \u3e 0.05). Logistic regressions indicated that outdoor time was not significantly associated with the MHO phenotype (OR: 0.99, 95% CI = 0.92-1.06; p = 0.694), while MVPA was significantly associated with the MHO phenotype (OR: 1.41, 95% CI = 1.01-1.98; p = 0.047) after adjusting for confounders.We conclude that outdoor time is not associated with the MHO phenotype, even though Canadian children living with obesity are more likely to be MHO with greater amounts of MVPA, regardless of whether these activities are completed outdoors or not

Resistance Training Contribute to the Aerobic Components of an Exercise Session in Adults but not as Much in Older Adults

International Journal of Exercise Science 10(3): 406-416, 2017. Previous research has indicated that active adults are able to achieve moderate intensity as measured via heart rate during a typical resistance training (RT) session. The main objective was to identify if overweight adults and older adults can reach aerobic moderate intensity at a rate comparable to adults displaying a recommended body mass index. Twenty participants in each group were asked to visit a fitness facility twice if they self-reported doing RT for a minimum two days per week. At the first session baseline characteristics and maximal lifting capacity for each RT exercise. At the second, intensity was monitored via heart rate monitor during a RT exercise program composed of 10 exercises targeting major muscle groups. Three sets of 10 repetitions at 70% of maximal load were completed for each exercise. Moderate intensity was defined as a minimum of 40% of heart rate reserve. The proportion of time spent at moderate to vigorous intensity between the comparison group and the overweight adult group was not significantly different, with a median (25th -75th) proportion time of 82.6% (69.2-94.6) versus 92.5% (73.3-99.1); p=.54 or an average time of 42 minutes versus 45 minutes. The older adults group, however, spent a lower proportion of time at moderate to vigorous intensity compared with the comparison group, 51.5% (22.0-86.6) or 24 minutes; p\u3c.01 compared with the comparison group. This study suggests that a good proportion of time spent doing RT can contribute to an aerobic component of the international guidelines, and therefore reduce the weekly time commitment especially for men and women age below 60 years old

Validation of Practical Tools to Identify Walking Cadence to Reach Moderate Intensity

International Journal of Exercise Science 12(4): 1244-1253, 2019. It is recommended that adults get at minimum 150 minutes of moderate-to-vigorous physical activity in bouts of 10 minutes or greaterevery week. Walking cadence (steps per minute) is one easy way to estimate intensity required, however tools that claim to quantify walking intensity via walking cadence have not been validated in adults. We aimed to validate: 1- the accuracy of walking cadence measurement by the Piezo RxD pedometer, Polar Stride Sensor Bluetooth Smart foot pod, and Garmin Ant+ foot pod at different speeds and slopes and 2- the ability of the Piezo RxD to identify bouts of walking at moderate intensity using walking cadence. Inclusion criteria included being aged 19+ and the ability to reach moderate intensity when walking without incline as determined by a treadmill cardiorespiratory fitness test to determine 40% of VO2reserve. Walking cadence measured from the three tools was compared to a manual count of walking cadence during a series of walking stages at several speeds (2.5-5.5 km/h) and inclines (0-15%). The ability of the Piezo RxD to quantify a 10-minute bout was determined by walking for 12 minutes at 40% of VO2reserve measured by indirect calorimetry. All correlations between manual walking cadence counts and all devices were significant regardless of speed (r ranging from 0.469 to 0.999; p£0.05) and slope (r ranging from 0.887 to 0.996; p£0.05). The Piezo RxD was able to correctly measure a 10-minute bout of walking at moderate intensity for 50 of 51 participants. We found that all walking cadence devices provided accurate measurements of walking cadence. The Piezo RxD is an effective tool to quantify bouts of walking done at a minimum of moderate intensity

Can Resistance Training Contribute to the Aerobic Components of the Physical Activity Guidelines?

International Journal of Exercise Science 7(4) : 278-285, 2014. To evaluate if resistance training can reach Moderate to Vigorous Intensity (MVI) and contribute to the aerobic component of the international physical activity guidelines. Sixteen participants aged between 20 and 35 were recruited. Heart rate was recorded by heart rate monitor during a resistance training program. Based on maximal heart rate, time spent at MVI (55-69% of maximal heart rate) was calculated. Participants displayed a HR equal or above MVI for 51.5% ± 21.7% of time. When stratifying by lower and upper body sessions, that proportion was median (25-75th); 75.0% (32.5%-89.2%) and 45.8% (30.0%-66.8%) respectively. Body mass (r=.68; p\u3c.01), body mass index (r=.54; p=.03), and leg press strength (r=.59; p=02) were positively associated with time spent at MVI. Assuming 10-minute bouts of aerobic exercise are not needed to achieve health benefits, it is possible to reach MVI with resistance training. Emphasis on the importance of performing resistance training should be done to reach the aerobic component of the physical activity guidelines and optimize health benefits. This provides an alternative option to those who may have difficulty or be unable to reach the required aerobic intensity by traditional aerobic exercises