<p> Recent evidence suggests that isometric handgrip training improves resting arterial blood pressure (BP) in normotensive and hypertensive individuals, however the mechanisms remain elusive. The purposes of the current investigation were to replicate the finding that 8 weeks of isometric handgrip training (IHG) improve resting BP in persons medicated for hypertension, to determine if training could improve aortic stiffness and to examine the acute cardiovascular response to IHG. Seventeen participants were recruited and familiarized with the laboratory and techniques used. Training consisted of 8 weeks of thrice weekly IHG training sessions using a pre-programmed handgrip dynamometer (4, 2-minute contractions separated by 4 minutes rest). Measurements of resting ABP (assessed by automated oscillometry), aortic stiffness (assessed by simultaneous ultrasound and applanation tonometry), and the acute cardiovascular response (heart rate, blood pressure, rate-pressure product, and cardiac output) were made at baseline and following 8 weeks of IHG training.</p> <p> Following training, there were no differences observed in resting systolic or diastolic systolic blood pressure, resting heart rate or cardiac output. Furthermore, handgrip training did not improve aortic distensibility or reduce stiffness index. The acute responses of heart rate, blood pressure, rate pressure product and cardiac output were not altered with training. In response to an acute bout of IHG there were significant increases seen in heart rate (55±2 to 65±3 BPM, p<0.01), blood pressure (systolic: 137.2±3.7 to 157.1±7.3; diastolic: 77.8±3.4 to 92.2±4.8 mmHg, p<0.01) and rate-pressure product (7369.4±302.0 to 10159.0±666.6 beatsxmmHg/min). Thus isometric handgrip training is a safe modality which does not appear to alter the stiffness of the proximal aorta or generate a significant cardiovascular strain in the acute phase.</p> / Thesis / Master of Science (MSc)

Les travaux de cette thèse s’inscrivent à la frontière des neurosciences et de la physiologie musculaire. Trois études se sont articulées de la préparation et l’exécution motrice. La première étude (A) a relié l'activité cérébrale à l'activité musculaire lors de la préparation motrice. Les résultats ont montré que des régions, telles que le cortex moteur primaire et l’aire motrice supplémentaire sont impliquées dans l'activité du muscle fléchisseur (FDS) alors que d’autres régions, telles que les ganglions de la base, les aires fronto-pariétales et le cervelet, sont impliquées dans l'activité du muscle extenseur (EDC). L’étude (B) a exploré le rôle du réseau cérébro-cérébelleux et du réseau striatal lors de l’exécution d’une tâche cognitive et motivationnelle. Les données ont révélé que la partie antérieure du lobule VI droit était activée par l'exécution motrice tandis que sa partie postérieure était spécifiquement activée par les encouragements verbaux. Les mesures de l’interaction psychophysiologique ont permis de faire immerger une boucle de connectivité fermée et formée par le cortex cérébral, le cervelet et les noyaux rouges. La troisième étude (C) concerne l’effet de la consigne réalisée lors de l’exécution motrice sur les paramètres neuromusculaires de FDS et EDC. Les résultats ont montré que la Force Maximale Volontaire, la Pente Maximale de Montée de Force et l’éléctromyographie associée étaient plus élevées (p < 0.05) avec la consigne accompagnée d’encouragement verbal. / The present work fits on the border of neurosciences and muscular physiology. Three studies explored the brain and muscle activities following motor preparation and execution. The first study (A) linked brain and muscle activity during motor preparation. The results revealed that regions (e.g primary motor cortex and supplementary motor area) are involved in the activity of the flexor muscle (FDS) while other regions (e.g basal ganglia, fronto-parietal areas and cerebellum) are involved in the activity of the extensor muscle (EDC). The study (B) explored the role of cerebro-cerebellar and striatal networks during the execution period of cognitive and motivational task. The data showed that the anterior part of the right lobule VI was activated by the motor task, while its posterior part was specifically activated by verbal encouragement. Measurements of psychophysiological interaction revealed a closed connectivity loop formed by the cerebral cortex, the cerebellum and the red nuclei. The third study (C) concerned the effect of instruction on neuromuscular parameters of FDS and EDC muscles during motor execution. The results showed that the Maximum Voluntary Force, the Maximum Rate of Force Development and the associated electromyographic signal are the highest (p < 0.05) with cognitive, motivational and verbal encouragement condition.

Title: Effect of cold water immersion on intermittent isometric forearm flexor contractions to failure in rock climbers Objectives: The aim of this study was to determine the effect of cold water immersion on intermittent isometric forearm flexor contraction to failure in rock climbers. Methods: Thirty-two climbers (15 male and 17 female) completed three intermittent trials to failure, on a climbing-specific handgrip dynamometer, on three separate visits to the laboratory. For each visit a different recovery strategy was employed: passive recovery (PAS), cold water immersion at 8 řC (CWI 8) or 15 řC (CWI 15). The force time integral (FTI - time of contraction multiplied by the force of contraction) was determined to assess intermittent performance. The tissue saturation index (TSI) and total haemoglobin (tHb) during isometric contractions from near-infrared spectroscopy (NIRS) were determined to assess hemodynamic changes. Differences between repeated trials and three recovery protocols, derived parameters NIRS, were assessed using repeated measures ANOVA with Bonferroni corrections. Results: There was no significant difference between conditions after trial one. In response to the PAS recovery condition there was a 10% and 22% decrease in FTI in the second and third trials, respectively. The PAS...

Title: Effect of cold water immersion on intermittent isometric forearm flexor contractions to failure in rock climbers Objectives: The aim of this study was to determine the effect of cold water immersion on intermittent isometric forearm flexor contraction to failure in rock climbers. Methods: Thirty-two climbers (15 male and 17 female) completed three intermittent trials to failure, on a climbing-specific handgrip dynamometer, on three separate visits to the laboratory. For each visit a different recovery strategy was employed: passive recovery (PAS), cold water immersion at 8 řC (CWI 8) or 15 řC (CWI 15). The force time integral (FTI - time of contraction multiplied by the force of contraction) was determined to assess intermittent performance. The tissue saturation index (TSI) and total haemoglobin (tHb) during isometric contractions from near-infrared spectroscopy (NIRS) were determined to assess hemodynamic changes. Differences between repeated trials and three recovery protocols, derived parameters NIRS, were assessed using repeated measures ANOVA with Bonferroni corrections. Results: There was no significant difference between conditions after trial one. In response to the PAS recovery condition there was a 10% and 22% decrease in FTI in the second and third trials, respectively. The PAS...