Evidence from epidemiological studies indicates that the incidence of cardiovascular morbidity and mortality peaks during the winter months. In fact, cold temperatures have been implicated as the putative factor associated with increased risk of hypertension as well as adverse cardiovascular events such as myocardial infarction, stroke, and fatal arrhythmias. In addition, exposure to cold temperatures ( PURPOSE: The aim of this proposed study was twofold 1) to evaluate the acute BP, wave refection (augmentation index, AIx), and cardiac autonomic responses during cold exposure with concurrent isometric exercise, and 2) to examine the effects of a 14-day course of L-cit supplementation on BP, arterial stiffness, wave reflection, and cardiac autonomic modulation during acute cold exposure at rest and during isometric exercise. We hypothesized that L-cit supplementation would reduce the BP, wave reflection, and cardiac sympathetic activity to cold exposure and isometric handgrip exercise (IHG). METHODS: In a crossover randomized fashion, 20 healthy young (23 ± 3 yr.) male participants volunteered for this study. Subjects were instructed to assume the supine position for 30 min inside an environmental chamber at cold (4ºC) or temperate ( temp,24ºC) conditions. Radial waveforms and heart rate variability (HRV) were obtained by means of applanation tonometry and heart rate monitor respectively. After 5 min of rest (RES) measurements the participants were asked to perform a 3 min IHG at 30% of their maximal voluntary contraction followed by a 3 min recovery (REC) period. After baseline measurements, subjects were assigned to either a Placebo (Maltodextrin, PL) or L-cit group for 14 days followed by 14 days of washout period, and 14 days of the second treatment. Cardiovascular function was evaluated during both cold and temp conditions before the first supplementation period, thereafter cardiovascular function was evaluated after 14 days of the first treatment, 14 days of washout period, and 14 days of a second treatment at 4ºC only. RESULTS: Height, weight, body mass index, and waist circumference were 1.77 ± 0.01 m, 84.7 ± 3.12 kg, 27.1 ± 1.0 kg/m2, and 88.5 ± 2.9 cm respectively. All 20 participants completed the experiments for the acute responses to cold versus temp and 16 completed the supplementation intervention (two dropped for personal reasons and two were not interested in participating in the intervention). Both, brachial systolic BP (BSBP) and aortic systolic BP (ASBP) were higher (P CONCLUSIONS: To our knowledge this is the first report showing hemodynamic responses to IHG during whole-body cold exposure and the effects of short-term after L-cit supplementation on these responses. These findings suggest that cold exposure imposes an additional increase in AIx and ΔEw during exercise that may ultimately lead to an attenuated cardiac vagal reactivation and sympathetic withdrawal after acute exercise. In addition, we demostarted that L-cit supplementation is an effective means to decrease the cold induced hypertensive responses and ΔEw at RES and REC, but not during IHG. In conclusion, L-cit supplementation may be a feasible adjuvant treatment to decrease the cold induced hypertensive response and ultimately provide cardioprotection in those exposed to low ambient temperature conditions. Further research is warranted in order to evaluate the effects of cold exposure and exercise in populations at increased cardiovascular risk. / A Dissertation submitted to the Department of Nutrition, Food and Exercise Sciences in partial fulfillment of the requirements for the degree of Doctor of
Philosophy. / Spring Semester 2012. / March 16, 2012. / blood pressure, cold exposure, heart rate variability, isometric exercise, L-citrulline, wave reflection / Includes bibliographical references. / Arturo Figueroa, Professor Directing Dissertation; Michael Overton, University Representative; Michael Ormsbee, Committee Member; Jeong-Su Kim, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_183523 |
| Contributors | Sanchez-Gonzalez, Marcos Angel (authoraut), Figueroa, Arturo (professor directing dissertation), Overton, Michael (university representative), Ormsbee, Michael (committee member), Kim, Jeong-Su (committee member), Department of Nutrition, Food, and Exercise Science (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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