Background and Rationale: Creatine phosphate (PCr) is degraded 𝘷𝘪𝘢 the creatine kinase (CK) enzyme to provide energy to rephosphorylate ADP back to ATP during high-intensity muscle contractions. We, and others, have previously shown that dietary creatine (Cr) loading can improve performance in short-duration, high intensity exercise in males and females. An increase in fat-free mass has also been reported, which was higher for males compared to females. It was unknown whether dietary Cr loading increases intramuscular [Cr] equally in both genders. The purpose of this investigation was to examine the effect of oral Cr loading upon [PCr] and [Cr] and exercise performance in both males and females. Methods: Twenty-seven healthy young subjects (n = 13 male, n = 14 female) participated in the investigation. Subjects performed an ischemic handgrip test, maximum voluntary contraction of dorsiflexors and knee extensors, a 30 s maximal cycling test (Wingate), and body composition (by DEXA scanning) was determined before and after supplementation with either Cr (n = 13) (5 g by mouth 4 •d⁻¹ x 5 d, followed by 5 g•d⁻¹ x 5 d) or placebo (pl; n = 14). Muscle biopsy samples were obtained before and after supplementation and were assayed for high-energy phosphates ([Cr], [PCr] and [ATP]). Results: Cr supplementation resulted in an increase in intramuscular total creatine concentration [TCr] (pl, 129.9 ± 13.8 to 132.9 ± 10.8 mMol•kg⁻¹ dw; Cr, 129.9 ± 11.6 to 146.4 ± 20.1 mMol•kg⁻¹ dw, p < 0.05) and a difference in [PCr] (pl, 72.8 ± 15.2 to 67.3 ± 4.3 mMol•kg⁻¹ dw; Cr, 70.9 ± 7.4 to 77.1 ± 13.2 mMol•kg⁻¹ dw), but had no effect on [Cr], and no differences in gender were observed. DEXA analysis showed no significant increase in total or fat-free mass; similarly, no improvements in maximum voluntary contractions were observed in either gender. In Wingate testing, males had a significant increase in peak power (pl, 971 ± 72 W to 989 ±76 W versus Cr, 994 ± 174 W to 1042 ± 154 W) and peak power per kilogram of body weight (pl, 12.8 ± 1.3 to 12.9 ± 1.1 W•kg⁻¹; Cr, 11.5 ± 1.1 to 12.1 ± 1.3 W•kg⁻¹) as a result of creatine supplementation, while females showed no significant difference. Conclusion: Creatine monohydrate supplementation at 20 g•d⁻¹ for 5 days resulted in an increase in muscle total creatine concentration for males and females, but did not affect body composition or maximum voluntary contraction. Males showed improved performance in absolute and relative peak power generation with supplementation while females did not. This may suggest that males and females respond differently to Cr supplementation. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22820 |
| Date | 08 1900 |
| Creators | MacLennan, Dan |
| Contributors | Tarnopolsky, Mark, Human Biodynamics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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