Scholarly Work - Health & Human Development
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/2920
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Item Low-dose creatine supplementation enhances fatigue resistance in the absence of weight gain(Elsevier, 2011-04) Miles, Mary; Rawson, E.S.; Stech, M.J.; Frederickson, Sara J.Objective: We examined the effects of 6 wk of low-dose creatine supplementation on body composition, muscle function, and body creatine retention. Methods: Twenty healthy men and women (21 ± 2 y old) were randomized to receive creatine (0.03 g • kg -1 • d-1; n=10, 4 women) for 6 wk in a double-blind placebo-controlled fashion. Participants were tested on two occasions before supplementation to establish a reliable baseline, and then were retested after supplementation. Testing included body composition, maximal strength (three-repetition maximal concentric knee extension at 180 degrees/s), muscle fatigue (five sets of 30 concentric knee extensions at 180 degrees/s), and plasma creatine concentration. Results: There were no significant differences in body mass, fat-free mass, fat mass, body fat percentage, total body water, or maximal strength in either group from before to after supple-mentation (all P > 0.05). After supplementation, plasma creatine increased significantly in the creatine group (+182%, P = 0.03), with no difference in the placebo group. Compared with baseline values, creatine-supplemented volunteers were more resistant to fatigue during sets 2 (7%), 3 (9%), 4 (9%), and 5 (11%) (all P < 0.05). In placebo-supplemented participants, there was no improvement in fatigue resistance during sets 2 (0%), 3 (1%), 4 (0%), and 5 (1%) (all P > 0.05). Conclusion: Ingesting a low dose (2.3 g/d) of creatine for 6 wk significantly increased plasma creatine concentration and enhanced resistance to fatigue during repeated bouts of high-intensity contractions.Item Interactive Effects of APOE Haplotype, Sex, and Exercise on Postheparin Plasma Lipase Activities(American Physiological Society, 2011) Miles, Mary; Seip, R.L.; Zoeller, Robert F.; Angelopoulos, T.J.; Salonia, J.; Bilbie, C.; Moyna, Niall M.; Visich, Paul S.; Pescatello, Linda S.; Gordon, P.M.; Tsongalis, Gregory J.; Bausserman, L.; Thompson, P.D.Hepatic lipase (HL) and lipoprotein lipase (LPL) activities (HLA, LPLA) modify lipoproteins and facilitate their binding to hepatic receptors. Apolipoprotein E (APOE) physically interacts with the lipases, and the three common haplotypes of the APOE gene (ε2, ε3, and ε4) yield protein isoforms (E2, E3, and E4, respectively) that are functionally different. Lipase activities themselves differ by sex and exercise training status. The interaction of APOE genotype, exercise training, and sex effects on lipase activities has not been studied. We measured postheparin plasma lipase activities in normolipidemic men and women with the three most common APOE genotypes, which are the haplotype combinations ε2/ε3 (n 53 ), ε3/ε3 (n 62), and ε4/ε3 (n 52), enrolled in 6 mo of aerobic exercise training. These haplotype combinations comprise an estimated 11.6, 62.3, and 21.3% of the population, respectively. Baseline HLA was 35% lower in women than in men (P 0.0001). In men but not women, HLA was higher in ε2/ε3 group compared with ε4/ε3 (P 0.01) and ε3/ε3 (P 0.05). Neither sex nor APOE genotype affected baseline LPLA. Training decreased HLA by 5.2% (P 0.018) with no APOE effect. The apparent increase in LPLA following exercise was significant and APOE dependent only when corrected for baseline insulin (P 0.05). Exercise decreased LPLA by 0.8 mol free fatty acid (FFA)·ml 1·h 1 ( 6%) in ε3/ε3 compared with the combined increases of 6.6% in ε2/ε3 and 12% in ε4/ε3 (P 0.018 vs. ε3/ε3). However, these differences were statistically significant only after correcting for baseline insulin. We conclude that common APOE genotypes interact with 1) sex to modulate HLA regardless of training status, with ε2/ε3 men demonstrating higher HLA than ε3/ε3 or ε4/ε3 men, and 2) aerobic training to modulate LPLA, regardless of sex, with ε3/ε3 subjects showing a significant decrease compared with an increase in ε2/ε3 and ε3/ε4 after controlling for baseline insulin.