Browsing by Subject "Thermoregulation"

Now showing 1 - 3 of 3
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    Respiratory Exchange Ratio is Not Associated with Slowing in the Marathon
    (2016-08) McGuirk, Erin
    Background: Previous research has shown that males slow more throughout the course of a marathon than females. Proposed reasons for differences in slowing include the fact that females oxidize proportionately more lipids and fewer carbohydrates during exercise when compared to males, and possible differences in thermoregulation. Respiratory exchange ratio (RER) can be used to estimate the ratio of fat to carbohydrates being metabolized. Purpose: To compare the degree of slowing (time in the first vs. second half of a marathon) between men and women, and determine if steady-state RER or ambient temperature differences predict the rate of slowing in male and female novice marathon runners. Methods: Chip times for 123 female and 44 male recreational marathon runners (21.0 ± 1.7yrs) were used to determine change in pace observed in the second half of the marathon compared to the first half. A two-mile time trial (2MI) was used to assess baseline fitness and pace for steady-state measurements. A submaximal 6-minute treadmill run at 75% of 2MI velocity was completed 1-3 weeks before the marathon. RER was collected using a metabolic cart (Medical Graphics Diagnostics, St. Paul, MN). Baseline measures and outcomes (RER and percent slowing) were analyzed using independent samples t-tests to detect differences between the groups (men vs. women and by year 2014, cool weather vs. 2015, warm weather). Univariate ANOVA tests were run to analyze the differences in percent slowing (%slowing) and RER by year and sex. Pearson’s Product Moment Correlation Coefficient (r) was used to determine the strength of the relationship between RER and %slowing as well as the relationship between %slowing and percent body fat (%BF), weight, height, body surface area (BSA), and BSA to mass ratio (BSA/M). Results: The mean %slowing for the total sample for 2014 and the total sample in 2015 was 14.1± 12.0% and 22.0 ± 16.5%, respectively (p<0.05). The mean %slowing for the combined group from 2014 and 2015 males and females was 20.6± 14.8% and 17.02 ± 14.8%, respectively (p <0.05). Females had a significantly lower RER during steady-state exercise in comparison with males (Female = 0.87 ± 0.05, Male = 0.89 ± 0.05, p<0.05). Sex and year were predictors of %slowing. There was no significant relationship between RER, temperature of marathon, weight, %BF, BSA, or BSA/M and %slowing in the total group, but RER and height were significantly related (p<0.05). Conclusion: Consistent with previous research, males slow more than females from the first to second half of the marathon. However, RER was not associated with slowing during the marathon. Temperatures of the race did affect the rate of slowing, but men and women were not affected differently. This suggests that pace maintenance is not due to substrate metabolism.
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    Testing and evaluation of three liquid cooling garments for use during spaceflight.
    (2010-09) Warpeha, Joseph M.
    Background: Extravehicular activity poses several dangers to astronauts. A major concern is the regulation of core temperature and thermal comfort in the context of an impermeable EMU microclimate and elevated energy expenditure rates for prolonged periods. Purpose: To identify the optimal features of each of three LCGs (MACS-Delphi, Russian Orlan, NASA LCVG) for maintaining core temperature and thermal comfort during exercise in mild (24 oC) and hot (35 oC) conditions. Methods: Four male and two female participants (aged 22-46 years) performed 10 trials (each with five 20-minute exercise stages and two rest stages) to account for all garment configurations (with/without hood) and temperature regimes. Metabolic (VO2, Ve, RER), temperature (core, skin), cardiovascular (HR, SBP, DBP, SaO2), local sweat rate, and skin wetness data were collected and analyzed during stages five (moderate exercise) and seven (rest). Whole body sweat rate and water flow parameters were collected pre- and post-trial. Results: Significant differences (p < or = 0.05) between garments were found for: skin temperature, HR, SBP, local and whole body sweat rate, and water flow rate. Discussion: There were several significant, yet few consistent, findings between the garments. Use of a cooling hood had no discernable effect. Amount of tubing coverage was related to whole body sweat rate while flow rate affected skin temperatures and local sweat rate. Conclusion: All three garments were similar in terms of regulating core temperature in a safe range (though not to the NASA standard of 37.2 oC) during physical exertion in moderate and hot environments. Future research is needed to identify the roles of adding a cooling hood and/or ventilation system to LCGs in addition to determining optimal water temperature, flow rate, tubing arrangement, and ergonomic design.
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    Thermoregulation and marathon performance: relationships of predictability of marathon performance, ambient weather conditions, BSA:MT, BSA:ML, percent body fat, and aerobic fitness
    (2012-11) Roach, Laura Elizabeth
    The purpose of this study was to observe individual variance in the ability to predict marathon performance from a two-mile time trial performance and determine whether the variance in predictability is influenced by thermoregulatory advantages of body size. Over three distinct marathon conditions, 126 (n =17 in 2010, n =42 in 2011, n =67 in 2012) aerobically-trained college physical activity students participated in pre- and post-anthropometric testing, a two-mile time trial on an indoor track, and concluded with the Eau Claire marathon. Between 72 and 98% of the variance in marathon performance could be explained by two-mile time trial performance. Variation of predicted performance from actual marathon performance was related to body surface area to mass ratio, body surface area to lean mass ratio, and percent body fat but depended on the race temperature, sex, and aerobic fitness. Notably, high body surface area to mass ratio was advantageous for sub-15 minute two-milers racing at an effective temperature of 12 degrees Celcius even though conditions were compensable. (r = 0.399, p< 0.033). The evidence shows that even in cold and mild conditions body surface area to mass ratio can affect marathon performance.