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Creatine Supplementation and Exercise Performance

Ronald J. Maughan

Creatine phosphate allows high rates of adenosine triphosphate resynthesis to occur in muscle and therefore plays a vital role in the performance of high-intensity exercise. Recent studies have shown that feeding large amounts of creatine (typically 20 g per day for 5 days) increases muscle total creatine (and phosphocreatine) content. The extent of the increase that is normally observed is inversely related to the presupplementation level. Vegetarians, who have a very low dietary creatine intake, generally show the largest increases. Creatine supplementation has been shown to increase performance in situations where the availability of creatine phosphate is important; thus, performance is improved in very high-intensity exercise and especially where repeated sprints are performed with short recovery periods. Creatine supplementation is widely practiced by athletes in many sports and does not contravene current doping regulations. There are no reports of harmful side effects at the recommended dosage.

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Dubious and Fraudulent Activities in Sports Nutrition

Ronald J. Maughan

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Dietary Supplements and the High-Performance Athlete

Ronald J. Maughan

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Changes for the New Year for IJSNEM

Ronald J. Maughan

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Development of Individual Hydration Strategies for Athletes

Ronald J. Maughan and Susan M. Shirreffs

Athletes are encouraged to begin exercise well hydrated and to consume sufficient amounts of appropriate fluids during exercise to limit water and salt deficits. Available evidence suggests that many athletes begin exercise already dehydrated to some degree, and although most fail to drink enough to match sweat losses, some drink too much and a few develop hyponatremia. Some simple advice can help athletes assess their hydration status and develop a personalized hydration strategy that takes account of exercise, environment, and individual needs. Preexercise hydration status can be assessed from urine frequency and volume, with additional information from urine color, specific gravity, or osmolality. Change in hydration during exercise can be estimated from the change in body mass that occurs during a bout of exercise. Sweat rate can be estimated if fluid intake and urinary losses are also measured. Sweat salt losses can be determined by collection and analysis of sweat samples, but athletes losing large amounts of salt are likely to be aware of the taste of salt in sweat and the development of salt crusts on skin and clothing where sweat has evaporated. An appropriate drinking strategy will take account of preexercise hydration status and of fluid, electrolyte, and substrate needs before, during, and after a period of exercise. Strategies will vary greatly between individuals and will also be influenced by environmental conditions, competition regulations, and other factors.

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Athletes and Supplements: Prevalence and Perspectives

Ina Garthe and Ronald J. Maughan

In elite sport, where opponents are evenly matched, small factors can determine the outcome of sporting contests. Not all athletes know the value of making wise nutrition choices, but anything that might give a competitive edge, including dietary supplements, can seem attractive. Between 40% and 100% of athletes typically use supplements, depending on the type of sport, level of competition, and the definition of supplements. However, unless the athlete has a nutrient deficiency, supplementation may not improve performance and may have a detrimental effect on both performance and health. Dietary supplements are classified as a subcategory of food, so manufacturers are not required to provide evidence of product safety and efficacy, nor obtain approval from regulatory bodies before marketing supplements. This creates the potential for health risks, and serious adverse effects have been reported from the use of some dietary supplements. Athletes who compete in sports under an anti-doping code must also realize that supplement use exposes them to a risk of ingesting banned substances or precursors of prohibited substances. Government systems of regulations do not include specific laboratory testing for banned substances according to the WADA list, so a separate regulatory framework to evaluate supplements for their risk of provoking a failed doping test is needed. In the high-performance culture typical of elite sport, athletes may use supplements regardless of possible risks. A discussion around medical, physiological, cultural, and ethical questions may be warranted to ensure that the athlete has the information needed to make an informed choice.

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Expanding Our Publication Schedule

Emily M. Haymes and Ronald J. Maughan

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Heat Acclimatization Strategies for the 1996 Summer Olympics

Scott J. Montain, Ronald J. Maughan, and Michael N. Sawka

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Fluid Replacement Strategies for Exercise in Hot Weather

Scott J. Montain, Ronald J. Maughan, and Michael N. Sawka

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Hematological Status of Male Runners in Relation to the Extent of Physical Training

John D. Robertson, Ronald J. Maughan, Ann C. Milne, and Ronald J.L. Davidson

Blood biochemical indices of iron status were measured in venous blood from 20 runners and 6 control subjects. All subjects were.male, ages 20 to 40 years, and stable with regard to body weight and degree of physical activity. Dietary analysis was undertaken using a 7-day weighed food intake. There was no evidence of iron deficiency: hemoglobin concentrations and serum femtin levels were within the normal population range for all individuals. However, serum ferritin was negatively correlated with the amount of training. Daily iron intake appeared to be adequate; iron intake was correlated with protein intake but not related to training or energy intake. Serum ferritin, an indicator of iron status, was significantly correlated with vitamin C intake but not iron intake. Serum transferrin concentration was higher in the group of athletes undertaking a high weekly training load compared with the control subjects, suggesting an alteration in iron metabolism although there was no evidence of increased erythropoiesis. The biological significance of this is unclear.