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Emma M. Crum, Matthew J. Barnes and Stephen R. Stannard

Pomegranate extract (POMx), a powder concentrate made from the peel, membrane, and pith of pomegranate fruit ( Punica granatum ) ( Seeram et al., 2008 ), has emerged as a potential ergogenic aid in endurance sport performance ( Trexler et al., 2014 ). The supplement was first investigated in

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Pablo Jodra, Raúl Domínguez, Antonio J. Sánchez-Oliver, Pablo Veiga-Herreros and Stephen J. Bailey

supplements claim to improve sports performance, such claims are not always supported by a firm foundation of robust scientific evidence. To overcome this ambiguity and to provide evidence-based recommendations for dietary supplementation to enhance sports performance, the International Olympic Committee has

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Marc Francaux and Jacques R. Poortmans

Context:

Allegations about side effects of creatine supplementation by athletes have been published in the popular media and scientific publications.

Purpose:

To examine the experimental evidence relating to the physiological effects of creatine supplementation.

Results:

One of the purported effects of oral creatine supplementation is increased muscle mass. A review of the literature reveals a 1.0% to 2.3% increase in body mass, which is attributed to fat-free mass and, more specifically, to skeletal-muscle mass. Although it is unlikely that water retention can completely explain these changes, increase in muscle-protein synthesis has never been observed after creatine supplementation. Indirect evidence based on mRNA analyses suggests that transcription of certain genes is enhanced. Although the effect of creatine on muscle-protein synthesis seems irrefutable according to advertising, this allegation remains under debate in the scientific literature. The kidneys appear to maintain their functionality in healthy subjects who supplement with creatine, even over several months.

Conclusion:

The authors, however, think that creatine supplementation should not be used by an individual with preexisting renal disease and that risk should be evaluated before and during any supplementation period. Even if there is a slight increase in mutagenic agents (methylamine and formaldehyde) in urine after a heavy load of creatine (20 g/day), their excretion remains within a normal range. No data are currently available regarding the potential production of heterocyclic amines with creatine supplementation. In summary, the major risk for health is probably associated with the purity of commercially available creatine.

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Joseph A. McQuillan, Julia R. Casadio, Deborah K. Dulson, Paul B. Laursen and Andrew E. Kilding

Athletes commonly use dietary supplements in an effort to enhance athletic performance. Recently, consumption of NO 3 − by way of either nitrate salt ( NaNO 3 − ) or beetroot juice has been found to improve both economy and performance, 1 potentially due to improved efficiency of mitochondrial

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Sergej M. Ostojic

The purpose of this study was to examine the effects of acute creatine-monohydrate supplementation on soccer-specific performance in young soccer players. Twenty young male soccer players (16.6 ± 1.9 years) participated in the study and were matched and allocated to 2 randomly assigned trials: ingesting creatine-monohydrate supplement (3 × 10-g doses) or placebo for 7 days. Before and after the supplementation protocol, each subject underwent a series of soccer-specific skill tests: dribble test, sprint-power test, endurance test, and vertical jump test. Specific dribble test times improved significantly in the creatine group (13.0 ± 1.5 vs. 10.2 ± 1.8 s; p < .05) after supplementation protocol. Sprint-power test times were significantly improved after creatine-monohydrate supplementation (2.7 ± 0.4 vs. 2.2 ± 0.5 s; p < .05) as well as vertical jump height (49.2 ± 5.9 vs. 55.1 ± 6.3 cm; p < .05) in creatine trial. Furthermore, dribble and power test times, along with vertical jump height, were superior in creatine versus placebo trial (p < .05) at post-supplementation performance. There were no changes in specific endurance test results within or between trials (p > .05). There were no between-trial differences in the placebo trial (p > .05). The main finding of the present study indicates that supplementation with creatine in young soccer players improved soccer-specific skill performance compared with ingestion of placebo.

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Kelly Pritchett, Robert C. Pritchett, Lauren Stark, Elizabeth Broad and Melissa LaCroix

or those participating in sports that require uniforms that minimize skin exposure ( Constantini et al., 2010 ). Given the strong evidence suggesting that vitamin D levels may be lower for certain sports during the winter months, recent research has examined the effects of vitamin D supplementation

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Emily M. Haymes

Vitamin and mineral supplements are frequently used by competitive and recreational athletes. Dietary deficiencies of most vitamins are not very common among athletes except in those who restrict their food intake in order to maintain body weight. Vitamins most likely to be deficient in the diet are folate, B6, B12, and E. Biochemical evidence of vitamin deficiencies in some athletes have been reported for thiamine, riboflavin, and B6. When the diet is deficient, vitamin supplements may improve performance but are not likely to be effective if the dietary intake is adequate. Some female athletes' diets are low in calcium, iron, and zinc. Low calcium intake may reduce peak bone mass in young women. Iron deficiency may impair performance and needs to be corrected with an iron supplement. Zinc supplements that exceed the RDA interfere with the absorption of copper and lower HDL-cholesterol.

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Luana Farias de Oliveira, Bryan Saunders and Guilherme Giannini Artioli

Sodium bicarbonate (SB) is an ergogenic supplement used to increase blood bicarbonate concentration, buffering capacity and, subsequently, high-intensity exercise capacity and performance ( McNaughton et al., 2016 ). There is a body of evidence indicating that SB is an effective ergogenic

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Duane Knudson

scholarship evaluation ( Hood & Wilson, 2001 ) of the three related fields of scholarship metrics: bibliometrics (library science), scientometrics (science), and informetrics (information science). This article addresses three issues in the use of bibliometrics to supplement research evaluations: the

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Kristin L. Jonvik, Jan-Willem van Dijk, Joan M.G. Senden, Luc J.C. van Loon and Lex B. Verdijk

supplementation when exercising under hypoxic conditions. This could be “local” tissue hypoxia, such as during anaerobic, high-intensity intermittent exercise ( Nyakayiru et al., 2017 ; Thompson et al., 2016 ; Wylie et al., 2013 ), or “systemic” normobaric/hypobaric hypoxia ( Carriker et al., 2016 ; Vanhatalo