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Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

5-2002

Committee Chair or Co-Chairs

Craig E. Broeder

Committee Members

Brian P. Rowe, Robert Acuff, Thomas W. Ecay Jr., William Joyner, William Stone

Abstract

This study tested the hypothesis that high intensity exercise, independent of total oxygen consumption, results in the most significant elevations in neutrophil (PMN) counts and blood oxidative stress (OS). This study also tested the hypothesis that active individuals have a blunted PMN and OS responses to acute exercise as compared to less active individuals. Nine males (18 – 30 yrs.) participated in 1 maximal (Max) and 3 sub-maximal exercise sessions. The 3 sub-max trials were: 1) LTplus, 45 min. above lactate threshold (LT), 2) LTminus, 45 min. below LT, and 3) LTplusCE, below LT until total oxygen consumption equaled (about 60 min) the LTplus trial. Blood was drawn before and immediately after, 1hr, and 2hr after exercise for measurement of PMN, myeloperoxidase enzyme (MPO), superoxide (O2-), vitamin C (C), urate (U), malondialdehyde (MDA), and lipid hydroperoxides (LPO). Results indicated an intensity-dependent post exercise PMN increase following Max and LTplus (p≤0.05). Post exercise MPO elevations were significant (p≤0.05) and similar for all trials except LTplus (NS). Furthermore, O2- was elevated immediately following Max exercise, while O2-/PMN was not. These data indicate that O2- elevations occur as PMN counts increase. Post-max, C (p=0.009), and U (p=0.034) were depleted indicating a significant reduction in plasma antioxidant fortifications. Subjects were separated according to high (n=5) and low (n=4) activity groups based on physical activity history questionnaires. Low activity subjects had higher PMN following maximal exercise. Pre exercise Low – High group differences neared significance for PMN (p=0.068) and O2- (p=0.09). High activity subjects had higher plasma C levels before and after exercise. Covariate analysis of dietary C intake demonstrated between group differences in plasma vitamin C levels at rest only. These results indicate that maximal intensity exercise resulted in the greatest increase in circulating PMNs and corresponding OS in blood plasma as identified by antioxidant depletion. This study clearly shows that exercise intensity, not total oxygen consumption, plays a role in post exercise neutrophil recruitment, and blood OS. Finally, these results suggest that regular physical activity and increased antioxidant intakes may attenuate the neutrophil rise and OS produced by maximal intensity exercise.

Document Type

Dissertation - Campus Only

Copyright

Copyright by the authors.

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