Browsing by Author "Christmas, Kevin Michael"
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Item The dose dependent effects of polyphenol supplementation on inflammatory markers following eccentric exercise(2012-05) Christmas, Kevin Michael; Coyle, Edward F., 1952-; Brothers, Matthew R.Unaccustomed eccentric exercise can lead to decreases in muscle force production, increases in soreness, swelling, stiffness, and discomfort. The purpose of this study was to test the dose response of pomegranate juice concentrate on serum markers of muscle permeability, inflammation, and total anti-oxidant status. To test this hypothesis, 45 healthy recreationally active males (22.3 ± 0.5 y, 73.8 ± 1.71 kg, 174.9 ± 0.9 cm) were recruited from the local Austin community for participation in this study. Subjects were disqualified from participation in the study if in the past 6 months they were engaged in an exercise training program. Subjects were placed into either the placebo group, the once-daily, or twice-daily pomegranate juice concentrate supplementation group. Subjects performed a total of 8 days of supplementation. On day 4, all subjects came to the laboratory and underwent an eccentric exercise protocol consisting of 2 minutes of downhill running at -10% grade at 7.5 mph repeated 10 times, resulting in ~20 minutes of total downhill running. Thereafter, subjects performed 50 eccentric elbow extensions each lasting 5 seconds using a weight equal to their concentric one-repetition maximum. Blood measures were made pre-exercise (baseline), and 2, 24, 48, 72, and 96 hours post exercise and analyzed for interleukin-6, creatine kinase, myoglobin, and total anti-oxidant status. Creatine kinase was significantly elevated at 96 hours post exercise, but with no significant differences between treatments. Myoglobin was significantly elevated above baseline at 2 and 96 hours, but with no differences between treatments. There was no effect for time or treatment on the total anti-oxidant status of the serum. Il-6 was significantly higher at 2 and 24 hours after exercise, but with no difference between treatments. The percent increase in interleukin-6 from baseline was significantly lower in the twice-daily POM supplementation group versus placebo (124.3 ± 9.4, 188.6 ± 16.0% of baseline; respectively) during the 2-96 hours following eccentric exercise, but no statistical difference between 1x and 2x or 1x and placebo was observed. This suggests that 8 days of supplementation with pomegranate juice concentrate twice a day significantly reduces the percent increase in a marker of inflammation (interleukin-6) during the 96 hours following eccentric exercise; however, neither supplement was different than the placebo in regards to all other measures.Item Mechanisms of pronounced and sustained microvascular vasoconstriction during cryotherapy(2015-08) Christmas, Kevin Michael; Brothers, Robert Matthew; Diller, Kenneth R; Coyle, Edward F; Tanaka, Hirofumi; Farrar, Roger PCryotherapy is the commonly used application of a cold compress to alleviate pain and swelling with injuries. However, while being one of the more well-known and commonly used therapies, there is limited systematic data collected in controlled environments showing benefits of cryotherapy. Many claims and perceived benefits of cryotherapy are based on empirical and anecdotal evidence, leaving much to be discovered. A typical cryotherapy protocol of 30 minutes can suppress blood flow, tissue temperature, and present with sustained vasoconstriction in the hours after treatment. This vasoconstriction can cause tissue death and necrosis, deemed non-freezing cold injuries, and results in roughly ~1,500 reported clinical cases per year in the United States. Furthermore, non-freezing cold injuries in the civilian population are a rare occurrence, but this type of injury, which relates to these investigations can reach epidemic proportions during times of war. Our primary findings from the research have implicated Rho kinase as being primarily involved in the formation of sustained vasoconstriction following cryotherapy treatment. Additionally, Rho kinase action impairs the temperature blood flow relationship that is necessary for abolishing much of the risk of ischemic injury. Secondary findings have furthered our knowledge of mechanisms of locally induced vasoconstriction and the significance of the sympathetic nerves in returning blood flow towards basal conditions following cryotherapy treatment. Finally, these investigations have shown that there appears to be limited involvement of nitric oxide in the lower ranges of blood flow. This finding might suggest that during a pronounced vasoconstrictive state (60-80% reduction in basal blood flow) much of the action of Rho kinase drives its activity by enhancing adrenergic activity. Our findings are generally in agreement with previous literature investigating mechanisms of cold-induced vasoconstriction. However, these previous studies typically made measurements on much smaller skin surfaces and also used much more mild temperatures for cooling. Accordingly, these findings outlined in the current studies improve our understanding of the vascular kinetics of cryotherapy use. We conclude that there needs to be a greater understanding and awareness provided to layman users of cryotherapy, allowing them to understand the risks and appropriate methods of application.