Creatine (Cr) is a nitrogen-containing compound endogenously synthesised in the kidneys, liver and pancreas from the amino acid arginine, with further additions from glycine and methionine. Optimal levels of muscle Cr and PCr may delay the onset of fatigue during muscle contraction that relies on the ATP-PCr energy system. Cr supplementation is considered necessary to increase skeletal muscle’s capacity to generate energy quickly, thereby enhancing maximal exercise performance. Researchers have paid little attention to the effect of Cr supplementation on aerobic endurance performance. Cr supplementation is also associated with an enhanced cellular anabolic state that may potentially prevent or lessen muscle atrophy associated with high-mileage training in ultradistance runners. The aim of this research was to investigate the ergogenic effects and safety of Cr supplementation over the short-, moderate-, and long term. For this purpose two population groups of interest were identified, namely well-trained male ultradistance runners and highly active male university students. Seventeen well-trained male ultradistance runners were paired and then, in a double-blind fashion, assigned to either a group consuming Cr monohydrate (CRE group; 38 ± 7.8 yrs; n = 9) or a group consuming placebo (PLA group; 37 ± 8.2 yrs; n = 8). Participants ingested 6 g/day supplement for six days. After post-test 1 (on day 7), the maintenance dosage was ingested at 3 g/day for 9 weeks. Participants adhered to an individually-tailored, high-intensity, high-volume sport-specific training programme. / Thesis (DPhil)--University of Pretoria, 2013. / gm2013 / Biokinetics, Sport and Leisure Sciences / unrestricted

The purpose of this thesis was to determine ways to maximize creatine uptake and retention during creatine supplementation. Since there are many factors that affect muscle creatine concentrations, a series of studies were performed. In the first study, the purpose was to determine if á-lipoic acid aided creatine uptake and retention. It was hypothesized that á-lipoic acid would increase creatine uptake, because it has been found to increase glucose disposal in animal studies and because creatine uptake has been found to be related to increased glucose transport. Results showed that phosphocreatine and total creatine increased following supplement intervention. In the second study, the purpose was to develop an optimal dose of creatine in order to minimize urinary excretion of creatine. It was hypothesized that individuals with more lean tissue mass would excrete less urinary creatine during consumption of the same loading dose. There was a high negative correlation between lean tissue mass and urine creatine excretion. Regression equations were developed for the relationship between lean tissue mass and urine total creatine and used to determine the amount of creatine to ingest relative to lean tissue mass that would result in minimal creatine losses in urine. Based on these results, a creatine dose of 0.22 [right arrow] 0.25 g/kg lean tissue mass/d was recommended. In the third study, the purpose was to determine if a habitual vegetarian diet resulted in lower muscle creatine and phosphocreatine concentrations compared to an omnivorous diet. A secondary purpose was to determine if creatine supplementation and weight training resulted in greater increases in muscle metabolite content, muscle fiber area, lean tissue mass, and strength in vegetarians compared to non-vegetarians. Results indicated that vegetarians had lower resting total creatine concentration, and that creatine supplementation and weight training led to greater increases in muscle phosphocreatine and total creatine in vegetarians compared to non-vegetarians (p < 0.0125). The supplement and exercise intervention eliminated the differences in intramuscular total creatine concentration that existed prior to the study. Type II muscle fiber area, lean tissue mass, total work output, and 1-RM bench press increased to a greater extent following creatine supplementation compared to placebo supplementation (p < 0.017), with no difference between vegetarians and non-vegetarians. (Abstract shortened by UMI.)

<p>[missing page:45]</p> / <p>BACKGROUND: Creatine monohydrate (CrM) supplementation during resistance exercise results in a greater increase in fat free mass (FFM), total body mass (TBM), and strength in young men and women. The purpose of the present investigation was to examine the interactive effects of creatine supplementation and resistance training on body composition, strength, and intramuscular total creatine concentration in older men and women.</p> <p>METHODS: Twenty-eight older men and women were randomly allocated, in a double blind fashion, to receive either CrM (n=14; CrM: 5g + 2g dextrose) or placebo (n=14; PL: 7g dextrose). Subjects participated in a 14 wk progressive, whole-body resistance training program. Pre-and post-training measurements included: 1 RM strength, isometric strength, body composition (TBM, FFM, %BF), muscle fiber area, and muscle total creatine and phosphocreatine.</p> <p>RESULTS: Training resulted in an increase in 1 RM strength for each of the 4 exercises (range = 26 - 60%) (p < 0.001), an increase in knee and dorsiflexion isometric strength (p < 0.001) and an improvement of performance on functional tasks (p < 0.001). Knee isometric strength was increased more for CrM (46.2%) as compared to PL (22.5%) (p < 0.05). Total body mass and lean body mass increased more for CrM (TBM: +1.2 kg; LBM: +1.7 kg) as compared to PL (TBM: -0.2 kg; LBM: 0.4 kg) (p < 0.05)</p> <p>CONCLUSIONS: We conclude that erM supplementation results in a greater increase in isometric knee extensor strength, total body mass and lean body mass during resistance training in older adults.</p> / Master of Science (MSc)

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