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  • Author: Michael G. Flynn x
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Darlene A. Sedlock, Man-Gyoon Lee, Michael G. Flynn, Kyung-Shin Park and Gary H. Kamimori

Literature examining the effects of aerobic exercise training on excess postexercise oxygen consumption (EPOC) is sparse. In this study, 9 male participants (19–32 yr) trained (EX) for 12 wk, and 10 in a control group (CON) maintained normal activity. VO2max, rectal temperature (Tre), epinephrine, norepinephrine, free fatty acids (FFA), insulin, glucose, blood lactate (BLA), and EPOC were measured before (PRE) and after (POST) the intervention. EPOC at PRE was measured for 120 min after 30 min of treadmill running at 70% VO2max. EX completed 2 EPOC trials at POST, i.e., at the same absolute (ABS) and relative (REL) intensity; 1 EPOC test for CON served as both the ABS and REL trial because no significant change in VO2max was noted. During the ABS trial, total EPOC decreased significantly (p < .01) from PRE (39.4 ± 3.6 kcal) to POST (31.7 ± 2.2 kcal). Tre, epinephrine, insulin, glucose, and BLA at end-exercise or during recovery were significantly lower and FFA significantly higher after training. Training did not significantly affect EPOC during the REL trial; however, epinephrine was significantly lower, and norepinephrine and FFA, significantly higher, at endexercise after training. Results indicate that EPOC varies as a function of relative rather than absolute metabolic stress and that training improves the efficiency of metabolic regulation during recovery from exercise. Mechanisms for the decreased magnitude of EPOC in the ABS trial include decreases in BLA, Tre, and perhaps epinephrine-mediated hepatic glucose production and insulin-mediated glucose uptake.

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Francis X. Pizza, Michael G. Flynn, Brian D. Duscha, Jill Holden and Eugene R. Kubitz

This investigation examined the effect of a carbohydrate loading regimen on high intensity, short duration ran performance. Using a random crossover design, 8 trained runners completed a 15-min submaximal run and a performance run to exhaustion after two dietary treatments. The mixed diet (MD) contained 4.0 ± 0.5 g · kg1 · d1 of carbohydrate (CHO) for 6 days. The experimental diet (HCD) contained 4.5 ± 0.5 g CHO · kg1 · d1 for 3 days followed by 8.2 ± 0.4 g CHO · kg1 · d1 for 3 days. Training consisted of daily runs of 90, 40, 40, 20, and 20 min at approximately 75% of VO2max. Day 6 was a rest day, and testing was completed on Day 7. Preexercise lactate, body weight, submaximal VO2, and heart rate did not differ significantly between treatments. Carbohydrate oxidation during submaximal running was higher (p < 0.05) after HCD than after MD. Time to exhaustion in the performance run was longer after HCD compared to MD. Results indicate that a carbohydrate loading regimen increases CHO oxidation during submaximal exercise and improves high intensity, short duration run performance.

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Kimberly M. White, Roseann M. Lyle, Michael G. Flynn, Dorothy Teegarden and Shawn S. Donkin

The purpose of this study was to test the effect of acute dairy calcium intake on exercise energy metabolism and endurance performance. Trained female runners completed two trials. Each trial consisted of a 90-min glycogen depletion run followed by a self-paced 10K time trial, conducted one hour after consumption of a high dairy (500 mg Ca+2) or low dairy (80 mg Ca+2) meal. During the 90-min run, blood samples and respiratory gases were collected. No treatment main effects of acute dairy intake were found for respiratory exchange ratio (RER), calculated fat oxidation, lactate, glycerol, or 10K time. Following this protocol, acute dairy calcium intake did not alter fat utilization or endurance performance in trained female runners.

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William A. Braun, Michael G. Flynn, Daniel L. Carl, Kathy K. Carroll, Todd Brickman and Charlie P. Lambert

Iron deficiency may lead to anemia and may result in compromised endurance exercise performance. Iron deficiency has also been reported to adversely affect the immune system and has been associated with attenuation of natural killer cell (NK) activity. This study was conducted to examine the relationship between iron status and NK activity in highly conditioned female athletes. Ten collegiate female swimmers (SWM) and 9 inactive females (SED) participated in this investigation. Resting blood samples were obtained and analyzed for serum iron and ferritin. NK activity (% lysis) was determined using a whole blood method (51Cr release assay). No significant relationship was found between iron and NK activity (r = 0.55, p = .09), nor between serum ferritin and NK activity (r = 0.33. p = .35) for SWM. ANOVA revealed significantly greater NK activity for SWM (51.63 ± 15.79%) versus SED (30.34 ± 13.67%). Serum ferritin levels were not significantly different between SWM (20.38±8.62Ƞg · ml−1) and SED (16.79±10.53Ƞg · ml−1), nor were iron values different between groups (16.54 ± 2.17 μmol · L−1 SWM; 11.92 ± 2.61 μmol · L−1 SED). A significant relationship between iron status and resting immune function could not be established. Exercise training may affect NK activity; however, the influence of iron status on immune function requires further evaluation.