Browsing by Author "Boldt, Kevin"

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    5th Rocky Mountain Muscle Symposium
    (Faculty of Kinesiology, 2023-05-19) Joumaa, Venus; Hessel, Anthony; Nishikawa, Kiisa; Millard, Matthew; Han, Seong-won; Bell, Kaylyn; Leonard, Tim; Kaya, Motoshi; Corr, David; Swank, Douglas; Corvelyn, Marlies; Sahani, Ridhi; Mazara, Nicole; Moo, Eng Kuan; Granzier, Henk; Oldshue, Ashley; Adkins, Amy; Loya, Amy; Boldt, Kevin; Desloovere, Kaat; Fukutani, Atsuki; Martino, Giovanni; De Beukelaer, Nathalie; Horslen, Brian; Agen, Anouk; Costamanga, Domiziana; Swank, Doug; Holt, Natalie
    Proceedings from the 4th Rocky Mountain Muscle Symposium, Canmore Nordic Centre, June 19-21, 2023.
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    Contractile Properties of Cardiac Muscle Following Increasing Doses of Chronic Exercise Training and Overtraining in Rats
    (2016) Boldt, Kevin; Herzog, Walter; MacIntosh, Brian; Syme, Doug; Tyberg, John
    The positive effects of chronic endurance exercise training on health and performance have been well documented. However, these positive effects have been evaluated primarily at the structural level, and it remains poorly understood how the heart muscle adapts mechanically to exercise training. In order to gain some understanding, we subjected three-month-old Sprague-Dawley rats to treadmill running for eleven weeks at one of three exercise volumes (moderate, high, and overtraining). Following training, hearts were excised and mechanical testing was completed on skinned trabecular bundles. Animals in the overtraining group experienced a significant loss in body mass, a withdrawal from food and drink, and became less active. The control, moderate, and high duration groups responded with a dose-dependent increase in heart mass and passive stresses, with no difference in active stress production. These trends were all reversed in the overtrained animals, despite presenting the greatest fitness on a graded treadmill test.
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    Exercise and Dietary Interventions in a Rat Model of Cardiac Adaptation
    (2020-12-09) Boldt, Kevin; Herzog, Walter; Syme, Douglas A.; MacIntosh, Brian R.; Reimer, Raylene A.
    Cardiovascular disease is one of the leading causes of death and disability, and is responsible for approximately one third of all deaths. Conversely, effective functioning of the heart is critical for performance in many sports and recreational activities. Therefore, developing effective strategies for preventing cardiovascular disease and promoting enhanced function of the heart is paramount. The overarching purpose of this thesis was to evaluate how cardiac muscle develops and ways to improve its function through dietary and exercise intervention. The work of this thesis was conducted in three phases. In the first phase, we compared both the structural and mechanical adaptations of the heart in response to aerobic and resistance exercise training. We concluded that exercise affects the structure and function of the heart, and its cellular components in a manner that is specific to the exercise protocol, and that there may be additional benefit of combining aerobic and resistance exercise training. In the second phase, we evaluated the effects of systematic protein supplementation in addition to aerobic exercise on the structural and mechanical properties of the heart. We concluded from these findings that a whey supplemented high-protein diet did not provide additional benefit for cardiac adaptation following aerobic exercise. In the final phase, we compared contractile properties of the heart muscle over the first year of life in rats. We concluded from these findings that many of the previously observed changes in systolic function associated with aging, occur between 12 and 21-33 months of age, while early signs of increased diastolic stiffness manifest sooner. Overall, though more work is required, this thesis presents evidence that structural and mechanical properties of the heart are adaptable and can be modified by either positive (exercise and diet) or negative (obesity and aging) factors.
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    Mechanical Adaptations of Skinned Cardiac Muscle in Response to Dietary-Induced Obesity During Adolescence in Rats
    (Canadian Science Publishing, 2020-03-05) Boldt, Kevin; Joumaa, Venus; Herzog, Walter; MacDonald, Graham
    Childhood obesity is a major risk factor for heart disease during adulthood, independent of adulthood behaviours. Therefore, it seems that childhood obesity leads to partly irreversible decrements in cardiac function. Little is known about how obesity during maturation affects the mechanical properties of the heart. The purpose of this study was to evaluate contractile properties in developing hearts from animals with dietary-induced obesity (high-fat high-sucrose diet (HFHS)). We hypothesized that obesity induced during adolescence results in decrements in cardiac contractile function. Three-week old rats (n=16) were randomized into control (chow) or dietary-induced obesity (HFHS) groups. Following 14 weeks on the diet, skinned cardiac trabeculae fibre bundle testing was performed to evaluate active and passive force, maximum shortening velocity, and calcium sensitivity. Rats in the HFHS group had significantly larger body mass and total body fat percentage. There were no differences in maximal active or passive properties of hearts between groups. Hearts from HFHS group rats had significantly slower maximum shortening and lower calcium sensitivity than controls. Decreased shortening velocity and calcium sensitivity in hearts of obese animals may constitute increased risk of cardiac disease in adulthood. Novelty Bullets • Cardiac muscle from animals exposed to an obesogenic diet during development had lower shortening velocity and calcium sensitivity than those from animals fed a chow diet. • These alterations in mechanical function may be a mechanism for the increased risk of cardiac disease observed in adulthood.
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    Mechanical and Structural Remodeling of Cardiac Muscle Following Aerobic and Resistance Exercise Training in Rats
    (2020-05-07) Boldt, Kevin; Joumaa, Venus; Turnbull, Jeannine; Fedak, Paul; Herzog, Walter
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    Proceedings of the 4th Rocky Mountain Muscle Symposium
    (2019-07-27) Joumaa, Venus; Hessel, Anthony; Nishikawa, Kiisa; Millard, Matthew; Han, Seong-won; Bell, Kaylyn; Leonard, Tim; Corr, David; Swank, Douglas; Corvelyn, Marlies; Sahani, Ridhi; Mazara, Nicole; Moo, Eng Kuan; Lieber, Rick; Kaya, Motoshi; Granzier, Henk; Oldshue, Ashley; Adkins, Amy; Loya, Amy; Boldt, Kevin; Desloovere, Kaat; Fukutani, Atsuki; Martino, Giovanni; De Beukelaer, Nathalie; Horslen, Brian; Agten, Anouk; Costamagna, Domiziana; Lee, Sabrina; Schwaner, Marie Janneke; Abbott, Emily; Binder-Markey, Benjamin; Siebert, Tobias; Lin, David; Fontana, Heiliane de Brito; Daley, Monica; Hahn, Daniel; Evangelidis, Pavlos; Knaus, Katherine; Smith, Ian; Deloovere, Kat; Kawakami, Yasuo; Hodson-Tole, Emma; Oliveira, Liliam; Ichinose, Hoshizora; Tillin, Neale; Raiteri, Brent; Seiberl, Wolfgang; Vaz, Marco; Cruz-Montecinos, Carlos; Griffiths, Robert; MacIntosh, Brian; Lourdes Rios, Jacqueline; Bossuyt, Fransiska
    Proceedings from the 4th Rocky Mountain Muscle Symposium, Canmore Nordic Centre, July 27-29, 2019