bluuebunny/crossref_metadata_2025 huggingface dataset:
Postprandial Glycemic Response in Three Male Endurance Athletes
Authors: Dunford Marie , Saunders Charlotte
Published: August 2016

The determination of blood glucose response to various carbohydrate foods may help athletes in their choice of preexercise feedings. This case study documented the postprandial glycemic responses of three male endurance athletes at rest after ingestion of 50-gram portions of three carbohydrate foods: graham crackers, orange juice, and oatmeal. Plasma glucose response differed in each subject for each test food. Two of the three subjects exhibited similar glycemic responses, but not to the same test food. Future studies will clarify the relationship between carbohydrate ingestion and postprandial glucose response.
Hypohydration during Exercise in Children: Effect on Thirst, Drink Preferences, and Rehydration
Authors: Meyer Flavia , Bar-Or Oded , Salsberg Avi , Passe Dennis
Published: August 2016

This study examined changes in children's thirst and drink preferences during exercise-induced hypohydration and their spontaneous rehydration during a 30-min recovery. Twenty-four 9- to 13-year-old children (14 females, 10 males) participated in four intermittent 90-rnin cycling sessions in the heat (, 20% relative humidity); the sessions differed in the drinks the children were sampling (apple, orange, water, and grape). Thirst and drink preferences were assessed (analog and category scales) while children dehydrated up to about 0.76% of their initial body weight. During 90 min dehydration, there was an increase in thirst intensity for all drinks. The grape was the preferable drink throughout the dehydration phase, but its desirability did not increase as much as the desirability of the orange, apple, and water drinks. During the 30-min recovery, most subjects rehydrated spontaneously, exceeding baseline levels by 0.76 ± 0.15% (M ± SEM) for grape, 0.40 ± 0.15 for apple, 0.71 ± 0.18 for orange, and 0.48 ± 0.16 for water. Although full rehydration was achieved with all drinks, the magnitude of rehydration was statistically greater with grape and orange than water and apple (p < .05). It was concluded that mild hypohydration during exercise increased children's thirst and drink desirability. In general, spontaneous overshoot of fluid consumption occurred during recovery.
Nutritional Status of Nationally Ranked Elite Bodybuilders
Authors: Kleiner Susan M. , Bazzarre Terry L. , Ainsworth Barbara E.
Published: August 2016

The nutritional status of 11 female and 13 male elite bodybuilders at the first drug-tested USA Championship was examined through food records kept by subjects. Diets were repetitive and monotonous, and average daily energy and protein contents were relatively similar for men and women. Percent calories from protein, fat, and carbohydrate were 39%, 12%, and 48% for females, and 40%, 11%, and 49% for males, respectively. Females consumed 0% vitamin D, 52% calcium, 76% zinc (as percents of RDA) and below the Estimated Safe and Adequate Dietary Allowance amounts for copper and chromium. Males consumed 46% of vitamin D RDA. Although dietary magnesium intakes were above the RDA, serum magnesium levels in females were below reference values, which should be investigated. Serum zinc levels were high in men and women. Eighty-one percent of females reported recurrent contest-related amenorrhea for 2 ± 1 months precontest. Dietary intakes of men were adequate but the restrictive intakes of women may place them at risk for calcium, copper, and chromium deficiencies.
Drinking Behavior and Exercise-Thermal Stress: Role of Drink Carbonation
Authors: Hickey Matthew S. , Costill David L. , Trappe Scott W.
Published: August 2016

This study investigated the influence of drink carbonation and carbohydrate content on ad libitum drinking behavior and body fluid and electrolyte responses during prolonged exercise in the heat. Eight competitive male runners completed three 2-hr treadmill runs at 60% in an environmental chamber maintained at and 40% RH. Three test drinks were used: 8% carbohydrate, low carbonation (8%-C); 8% carbohydrate, noncarbonated (8%-NC), and water (0%-NC). Blood samples were taken preexercise (0), at 60 and 120 min of exercise, and at 60 min of recovery (+60 min). The data suggest that while reports of heartburn tend to be higher on 8% carbohydrate drinks than on 0%-NC, this does not appear to be a function of drink carbonation. Similarly, the increased frequency of heartbum did not significantly reduce fluid consumption either during exercise or during a 60-min recovery period. Importantly, no differences were observed between fluid and electrolyte, or thermoregulatory responses to the three sport drinks. Thus, consumption of low-carbonation beverages does not appear to significantly influence drinking behavior or the related physiological responses during prolonged exercise in the heat.
The Use of Nutritional Ergogenic Aids in Sports: Is It an Ethical Issue?
Authors: Williams Melvin H.
Published: August 2016

As nutritional technology advanced, scientists have been able to synthesize and manufacture all known nutrients, and many of their metabolic by-products, essential to human physiology. Many of these substances are theorized to possess ergogenic potential when take in quantities or forms normally not found in typical foods or diets. Research, although limited in most cases, supports the ergogenicity of some nutrients (e.g., creatine) when consumed in substantial amounts, suggesting such nutrients may function as drugs or nutraceuticals. The International Olympic Committee (IOC) doping legislation stipulates that any physiologic substance taken in abnormal quantity with the intention of artificially and unfairly increasing performance should be construed as doping, violating the ethics of sport performance. Given this stipulation, the IOC and other athletic-governing organizations should consider the legality and ethics underlying the use of ergogenic nutraceuticals in sport.
Working with College Athletes, Coaches, and Trainers at a Major University
Authors: Clark Kristine Larson
Published: August 2016

Athletic departments in colleges and universities are beginning to recognize the role a sports nutrition professional plays in providing both clinical nutrition services to athletes and nutrition education programs to teams, coaches, and trainers. Traditionally, sports nutritionists have been viewed as capable of counseling athletes toward improved nutrition behaviors for improved performance outcomes. More globally, a sports nutritionist at a major university can develop and implement nutrition education programs for athletes that can be implemented in alternative situations to effect the greater student body. Menu changes in dining facilities, expanded dining hours, and campus workshops on eating disorders, weight gain, or weight loss are examples of programs created by a university sports nutritionist.
Nutritional Intake during an Ultraendurance Running Race
Authors: Eden Barbara D. , Abernethy Peter J.
Published: August 2016

The food and fluid intake of a male ultraendurance runner was recorded throughout a 1,005-km race completed over 9 days. The nutrient analysis showed an average daily energy intake of 25,000 kJ with 62% from carbohydrate, 27% from fat, and 11% from protein. Carbohydrate intake was estimated to be 16.8 g · · . The protein intake was estimated to be 2.9 g · · and water intake to be 11 L per day. These figures are within the recommended levels for ultraendurance athletes (2, 10). Food and fluid were consumed in small amounts every 15 to 20 min to ensure maintenance of blood glucose levels and adequate hydration. This case study suggests that if the guidelines for prolonged exercise are followed, then athletes can successfully complete ultraendurance events.
Carbohydrate, Fluids and Electrolyte Requirements of the Soccer Player: A Stewiew
Authors: Hawley John A. , Dennis Steven C. , Noakes Timothy D.
Published: August 2016

Soccer requires field players to exercise repetitively at high intensities for the duration of a game, which can result in marked muscle glycogen depletion and hypoglycemia. A soccer match places heavy demands on endogenous muscle and liver glycogen stores and fluid reserves, which must be rapidly replenished when players complete several matches within a brief period of time. Low concentrations of muscle glycogen have been reported in soccer players before a game, and daily carbohydrate (CHO) intakes are often insufficient to replenish muscle glycogen stores, CHO supplementation during soccer matches has been found to result in muscle glycogen sparing (39%), greater second-half running distances, and more goals being scored with less conceded, when compared to consumption of water. Thus, CHO supplementation has been recommended prior to, during, and after matches. In contrast, there is currently insufficient evidence to recommend without reservation the addition of electrolytes to a beverage for ingestion by players during a game resulting in sweat losses of < 4% of body weight.
Effect of L-Carnitine Supplementation on Muscle and Blood Camitine Content and Lactate Accumulation during High-Intensity Sprint Cycling
Authors: Barnett Christopher , Costill David L. , Vukovich Mathew D. , Cole Kevin J. , Goodpaster Bret H. , Trappe Scott W. , Fink William J.
Published: August 2016

This study examined the effects of 14 days of L-camitine supplementation on muscle and blood camitine fractions, and muscle and blood lactate concentrations, during high-intensity sprint cycling exercise. Eight subjects performed three experimental trials: control 1 (CON I, Day 0), control I! (CON II, Day 14), and L-camitine (L-CN, Day 28). Each trial consisted of a 4-rain ride at 90% , followed by a rest period of 20 min, and thee five repeated 1-min rides at 115% (2 min rest between each). Following CON n, all subjects began dietary supplementation of L-camitine for a period of 14 days (4 g/day). Plasma total acid soluble and free camitine concentrations were significantly higher (p < .05) at all time points following supplementation. L-camitine supplementation had no significant effect on muscle camitine content and thus could not alter lactate accumulation during exercise.
Plasma Glucose Levels after Prolonged Strenuous Exercise Correlate Inversely with Glycemic Response to Food Consumed before Exercise
Authors: Thomas Diana E. , Brotherhood John R. , Miller Janette Brand
Published: August 2016

It was hypothesized that slowly digested carbohydrates, that is, low glycemic index (GI) foods, eaten before prolonged strenuous exercise would increase the blood glucose concentration toward the end of exercise. Six trained cyclists pedaled on a cycle ergometer at 65-70% 60 min after ingestion of each of four test meals: a low-GI and a high-GI powdered food and a low-GI and a high-GI breakfast cereal, all providing 1 g of available carbohydrate per kilogram of body mass. Plasma glucose levels after more that 90 min of exercise were found to correlate inversely with the observed GI of the foods (p < .01). Free fatty acid levels during the last hour of exercise also correlated inversely with the GI (p < .05). The findings suggest that the slow digestion of carbohydrate in the preevent food favors higher concentrations of fuels in the blood toward the end of exercise.
Supplementation Patterns of Competitive Male and Female Bodybuilders
Authors: Brill Janet Bond , Keane Michele W.
Published: August 2016

This study described the prevalence of supplement use by 309 male and female competitive bodybuilders. Participants completed a comprehensive survey detailing their supplementation patterns with respect to frequency of product use, spending characteristics, and reasons for use. Supplement use varied with training phase. Protein powder was more popular in the bulking phase, ammo acids and fat burners in the cutting phase. Fifty-nine percent of respondents spent $25-100 per month; 4.9% spent over $150. The most popular reason for supplement use was “to meet extra demands of heavy training.” In the bulking phase, both weight gain and anabolic supplements were reportedly consumed more frequently by men than women. In the cutting phase, “fat burners” were reportedly consumed by a greater percentage of females than males. The information provided by this study can help sport nutritionists identify supplements most often consumed by bodybuilders and can aid counselors as they guide bodybuilders towards more healthful nutrition practices.
Calcium Intakes of Adolescent Female Gymnasts and Speed Skaters: Lack of Association with Dieting Behavior
Authors: Webster Brenda L. , Barr Susan I.
Published: August 2016

Calcium intake and its association with dieting behavior were assessed in female adolescents competing in an aesthetic and a nonaesthetic sport (gymnastics and speed skating). Athletes were 25 skaters and 32 gymnasts competing at a provincial level or higher. Calcium intake was assessed by food frequency questionnaire; dieting behavior by the Eating Attitudes Test Dieting subscale; and body composition by skinfolds, height, and weight. Mean calcium intakes of both groups of athletes exceeded Canadian recommendations, and skaters' mean intakes exceeded U.S. recommendations; however, many individuals had low intakes. Gymnasts were leaner than skaters and had lower calcium intakes, but this difference was not associated with Dieting subscale scores, which were similar between sports and were not correlated with calcium intake. Athletes had higher mean calcium intakes than normally active adolescents studied (measured with a similar protocol) and had lower Dieting subscale scores. Thus, although calcium intakes of some athletes require attention, sport participation was associated with increased intakes. Also, for these athletes, dieting behavior did not directly interfere with calcium intake.
The Effects of Carbohydrate Loading on Muscle Glycogen Content and Cycling Performance
Authors: Rauch Laurie H.G. , Rodger Ian , Wilson Gary R. , Belonje Judy D. , Dennis Steven C. , Noakes Timothy D. , Hawley John A.
Published: August 2016

This study compared the effects of supplementing the normal diets of 8 endurance-trained cyclists with additional carbohydrate (CHO), in the form of potato starch, for 3 days on muscle glycogen utilization and performance during a 3-hr cycle ride. On two occasions prior to the trial, the subjects ingested in random order either their normal CHO intake of 6.15 ± 0.23 g/kg body mass/day or a high-CHO diet of 10.52 ± 0.57 g/kg body mass/day. The trial consisted of 2 hr of cycling at ~75% of with five 60-s sprints at 100% at 20-min intervals, followed by a 60-min performance ride. Increasing CHO intake by 72 ± 9% for 3 days prior to the trial elevated preexercise muscle glycogen contents, improved power output, and extended the distance covered in 1 hr. Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.
Dietary Intake of Two Elite Male Cyclists during 10-Day, 2,050-Mile Ride
Authors: Gahel Kathe A. , Aldous Adrienne , Edgington Chad
Published: August 2016

Food and fluid intake of 2 male cyclists was assessed to describe dietary intakes of athletes participating in an endurance ride. Cyclists rode 15 to 18 hr each day for 10 days to travel 2,050 miles on the original Pony Express Trail over seven major mountain ranges. Food and fluids were weighed or measured by researchers. Average kilocalorie intake was 7,125 ± 340 (M ± SEM), or 113 kcal/kg/day. Percentages of protein, carbohydrate, and fat kilocalories were 10, 63, and 27, respectively, with 44% of the carbohydrate kilocalories from simple sugars, cookies, sweetened drinks, and candy. Vitamin and mineral intakes were two to three times the RDA for most vitamins and minerals. Total fluid intake averaged 10.5 L per day with an average of 620 ml/hr of riding time. Of fluid intake, 54% was water. Cyclists traveling long distances need a variety of high-calorie foods and ample amounts of fluids to maintain performance for this type of event.
U.S. Government Raises Serious Questions about Reliability of U.S. Department of Agriculture's Food Composition Database
Authors: Katch Frank I.
Published: August 2016

A recent government report from the General Accounting Office concludes that some Handbook 8 nutritional data have so little documentation on how the data were produced that it is possible some nutrient values are not reliable, and that HNIS does not appropriately direct the generation of food composition data under its contracted laboratory studies. The report recommends that the Secretary of Agriculture direct the HNIS administrator to develop (a) specific quality assurance criteria for HNIS staff to use in evaluating food composition data obtained from others before the data are included in Handbook 8, and (b) procedures to better direct the generation of food composition data under HNIS' contracts.
Effect of Acute Potassium-Magnesium Aspartate Supplementation on Ammonia Concentrations during and after Resistance Training
Authors: Tuttle Jay L. , Potteiger Jeffrey A. , Evans Blanche W. , Ozmun John C.
Published: August 2016

This study examined the effects of aspartate supplementation (ASP) on plasma ammonia concentrations ([]) during and after a resistance training workout (RTW). Twelve male weight trainers were randomly administered ASP or vitamin C in a crossover, double blind protocol, each trial separated by 1 wk. ASP and vitamin C were given over a 2-hr period beginning 5 hr prior to the RTW. The RTW consisted of bench, incline, shoulder, and triceps presses, and biceps curls at 70% of one repetition maximum (1-RM). After the RTW a bench press test (BPT) to failure at 65% of 1-RM was used to assess performance. [] was determined preexercise, 20 and 40 min midworkout, immediately postexercise, and 15 min postexercise. Treatment-by-time ANOVAs, paired t tests, and contrast comparisons were used to identify mean differences. No significant differences were observed between treatments for [] or BPT. [] increased significantly from Pre to immediately postexercise for both the ASP and vitamin C trials. Acute ASP supplementation does not reduce [] during and after a high intensity RTW in weight trained subjects.
Effects of Carbohydrate Supplementation during Intense training on Dietary Patterns, Psychological Status, and Performance
Authors: Kreider Richard B. , Hill Dawn , Horton Greg , Downes Michael , Smith Sarah , Anders Beth
Published: August 2016

The purpose of this study was to determine the effects of carbohydrate supplementation during intense training on dietary patterns, psychological status, and markers of anaerobic and aerobic performance. Seven members of the U.S. National Field Hockey Team were matched to 7 team counterparts (N = 14). One group was blindly administered a carbohydrate drink containing 1 g·kg−1 of carbohydrate four times daily, while the remaining group blindly ingested a flavored placebo during 7 days of intense training. Subjects underwent pre- and posttraining aerobic and anaerobic assessments, recorded daily diet intake, and were administered the Profile of Mood States (POMS) psychological inventory prior to and following each practice. Results revealed that the carbohydrate-supplemented group had a greater (p < .05) total energy intake, carbohydrate intake, and change (pre vs. post) in time to maximal exhaustion following training while reporting less postpractice psychological fatigue. However, no significant differences were observed in remaining psychological, physiological, or performance-related variables.
Dietary Intake and Nutritional Status of Athletic and Nonathletic Children in Early Puberty
Authors: Rankinen Tuomo , Fogelholm Mikael , Kujala Urho , Rauramaa Rainer , Uusitupa Matti
Published: August 2016

Dietary intakes, trace element status, and anthropometric measures were studied in 12- to 13-year-old boys (n = 49) playing ice hockey (AB) and in 11- to 12-year-old girls who were gymnasts, figure skaters, and runners (AG; n = 43), Thirty-five boys (CB) and 53 girls (CG) not involved in supervised sports were controls. After adjustment for sexual maturation, ABs had larger upper arm muscle circumference than CBs. The sum of four skinfolds was smaller in AGs than in CGs. The intake of energy and all micronutrients examined was higher in ABs than in CBs. Micronu-trient Intakes were not different between AGs and CGs. Compared to CBs, serum ferritin and copper concentrations were lower, but serum zinc concentration was higher in ABs. No differences in trace element status were found between AGs and CGs. Blood investigations did not indicate inadequate trace element status in any of the groups studied.
Creatine Supplementation and Exercise Performance
Authors: Maughan Ronald J.
Published: August 2016

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.
Fluid-Electrolyte Balance Associated with Tennis Match Play in a Hot Environment
Authors: Bergeron Michael F. , Maresh Carl M. , Armstrong Lawrence E. , Signorile Joseph F. , Castellani John W. , Kenefick Robert W. , LaGasse Kent E. , Riebe Deborah A.
Published: August 2016

Twenty (12 male and 8 female) tennis players from two Division I university tennis teams performed three days of round-robin tournament play (i.e., two singles tennis matches followed by one doubles match per day) in a hot environment (32.2 ± and 53.9 ± 2.4% rh at 1200 hr), so that fluid-electrolyte balance could be evaluated. During singles play, body weight percentage changes were minimal and were similar for males and females (males -1.3 ± 0.8%, females -0.7 ± 0.8%). Estimated daily losses (mmol · ) of sweat sodium (Na+) and potassium (K+) (males, 158.7, 31.3; females, 86.5, 18.9) were met by the players' daily dietary intakes (mmol · ) of these electrolytes (males, 279.1 ± 109.4, 173.5 ± 57.7; females, 178.9 ± 68.9, 116.1 ± 37.5). Daily plasma volume and electrolyte (Na+, ) levels were generally conserved, although, plasma [Na+] was lower (p < .05) on the morning of Day 4. This study indicated that these athletes generally maintained overall fluid-electrolyte balance, in response to playing multiple tennis matches on 3 successive days in a hot environment, without the occurrence of heat illness.
Glucose and Insulin Responses after Commonly Used Sport Feedings before and after a 1-hr Training Session
Authors: Hofman Zandrie , Kuipers Harm , Keizer Hans A. , Fransen Erik J. , Servais Roderique C.J.
Published: August 2016

This investigation examined the plasma glucose and insulin response in 6 trained athletes after consumption of four commercially available sport feedings 2 hr before as well as immediately after 1 hr of running under common training conditions. Four feedings were compared: Feeding 1, 160 g CHO/400 ml; Feeding 2, 69 g CHO/400 ml; Feeding 3, 69 g CHO + 6 g protein/400 ml; and Feeding 4, solid 69 g CHO + 5 g protein + 4 g fat. Before the training session, there were no differences between the four sport feedings in the area under the glucose and insulin curves and the insulin/glucose ratio. However, after exercise, Feeding 2 resulted in a significantly greater area under the glucose curve compared with Feedings 1, 3, and 4 (respectively, 352 vs. 241, 251, and 182) and a significantly lower insulin/glucose ratio compared with Feeding 1 (respectively, 6.2 vs. 15.8). Therefore, it is concluded that the kind of sport feeding may influence postexercise glucose and insulin responses.
Effects of Carbohydrate Feeding before and during Prolonged Exercise on Subsequent Maximal Exercise Performance Capacity
Authors: El-Sayed Mahmoud S. , Rattu Angelheart J.M. , Roberts Ian
Published: August 2016

The study examined the effect of carbohydrate ingestion on exercise performance capacity. Nine male cyclists performed two separate trials at 70% for 60 min followed by a maximal ride for 10 min. During trials subjects were fed either an 8% glucose solution (CHO) or a placebo solution (PL), which were administered at rest and during and immediately after submaximal exercise. Statistical analyses indicated that glucose levels at rest increased significantly 15 min after the ingestion of CHO compared to PL. At 30 and 60 min during submaximal exercise, plasma glucose levels decreased significantly in the CHO but not in the PL trial. Following the performance ride, glucose levels increased significantly only during the CHO test trial. Free fatty acids did not change significantly during testing trials. The maximal performance ride results showed that in the CHO trial, a significantly greater external work load was accomplished compared to the PL trial. It is concluded that CHO ingestion improves maximal exercise performance after prolonged exercise.
Effects of Multibuffer Supplementation on Acid-Base Balance and 2,3-Diphosphoglycerate Following Repetitive Anaerobic Exercise
Authors: Kraemer William J. , Gordon Scott E. , Lynch James M. , Pop Mariana E.M.V. , Clark Kristine L.
Published: August 2016

The purpose of this investigation was to determine the effects of a 3.5-day dietary multibuffer supplement (containing predominantly inorganic phosphate, or Pj, along with bicarbonate and carnosine, i.e., PhosFuel™) on repetitive (four trials separated by 2 min rest) Wingate test (WT) performances and whole blood 2,3-diphosphoglycerate (2,3-DPG) concentrations in 10 recreationally trained road cyclists (T) and 10 normally active but untrained (UT) men. A 2-week washout period was utilized between experimental sessions. Venous blood samples were obtained via cannula once before exercise (baseline), immediately post each WT, and 3 min after the final WT (recovery). The data indicate that this supplement does not affect acid-base status with following intense anaerobic exercise and does not improve repetitive WT performance. However, the supplement does enhance post-exercise levels of 2,3-DPG and the 2,3-DPG/Hb ratio in recreationally trained cyclists while improving acute recovery of peak power in these men.
Sensory Acceptability of Meat and Dairy Products and Dietary Fat in Male Collegiate Swimmers
Authors: Guinard lean-Xavier , Seador Kimberly , Beard John L. , Brown Peter L.
Published: August 2016

This study was undertaken to determine whether high-level training alters food choice behavior with regard to meat and dairy products because of their high fat content. Twenty male collegiate swimmers were compared to 20 male sedentary students for dietary fat intake, nutrition knowledge, and liking of meat and dairy products. There was no significant difference between the two groups for restraint, energy intake, dietary fat intake, and energy derived from fat. Nutrition knowledge, energy derived from saturated fat, and cholesterol intake, however, were significantly higher in the athletes. The two groups did not differ in their hedonic ratings of flavor or in their overall degree of liking of the meat and dairy products, and the athletes actually liked the appearance and texture of the products significantly more than did the sedentary students. This study shows that the sensory appeal of fat-containing animal products is not affected in male swimmers by a high level of exercise.
Creatine and Its Application as an Ergogenic Aid
Authors: Greenhaff Paul L.
Published: August 2016

Phosphocreatine (PCr) availability is likely to limit performance in brief, high-power exercise because the depletion of PCr results in an inability to maintain adenosine triphosphate (ATP) resynthesis at the rate required. It is now known that the daily ingestion of four 5-g doses of creatine for 5 days will significantly increase intramuscular creatine and PCr concentrations prior to exercise and will facilitate PCr resynthesis during recovery from exercise, particularly in those individuals with relatively low creatine concentrations prior to feeding. As a consequence of creatine ingestion, work output during repeated bouts of high-power exercise has been increased under a variety of experimental conditions. The reduced accumulation of ammonia and hypoxanthine in plasma and the attenuation of muscle ATP degradation after creatine feeding suggest that the ergogenic effect of creatine is achieved by better maintaining ATP turnover during contraction.
Antioxidants, Carnitine, and Choline as Putative Ergogenic Aids
Authors: Kanter Mitchell M. , Williams Melvin H.
Published: August 2016

Three nutritional products that have very different mechanisms of action are antioxidant vitamins, carnitine, and choline. Antioxidant vitamins do not appear to have a direct effect on physical performance in well-fed people but have been touted for their ability to detoxify potentially damaging free radicals produced during exercise. Carnitine purportedly enhances lipid oxidation, increases VO2max, and decreases plasma lactate accumulation during exercise. However, studies of carnitine do not generally support its use for ergogenic purposes. Choline supplements have been advocated as a means of preventing the decline in acetylcholine production purported to occur during exercise; this decline may reduce the transmission of contraction-generating impulses across the skeletal muscle, an effect that could impair one’s ability to perform muscular work. However, there are no definitive studies in humans that justify choline supplementation. Much of the scientific data regarding the aforementioned nutrients are equivocal and contradictory. Their potential efficacy for improving physical performance remains largely theoretical.
Carbohydrates, Branched-Chain Amino Acids, and Endurances: The Central Fatigue Hypothesis
Authors: Davis J. Mark
Published: August 2016

The mechanisms of central fatigue are largely unexplored, but the central fatigue hypothesis suggests that increased brain serotonin (5-HT) can cause a deterioration in sport and exercise performance. There is now convincing evidence that exercise-induced increases in the plasma free tryptophan (f-TRP)/branched-chain amino acids (BCCA) ratio are associated with increased brain 5-HT and the onset of fatigue during prolonged exercise. Furthermore, when drugs are administered to alter brain 5-HT, they have the predicted effects on exercise performance. The influence of nutritional manipulations of f-TRP/BCCA on performance is less well established. The effects of BCCA supplementation on exercise performance are mixed, and the published studies often suffer from methodological flaws. Alternatively, dramatic reductions in f-TRP/BCCA and enhanced performance accompany carbohydrate feedings during prolonged exercise. However, it is difficult to distinguish between the effects of carbohydrate feedings on mechanisms that reside in the brain versus the muscles themselves.
Do Athletes Need More Dietary Protein and Amino Acids?
Authors: Lemon Peter W. R.
Published: August 2016

The current recommended daily allowance (RDA) for protein is based primarily on data derived from subjects whose lifestyles were essentially sedentary. More recent well-designed studies that have employed either the classic nitrogen balance approach or the more technically difficult metabolic tracer technique indicate that overall protein needs (as well as needs for some specific individual amino acids) are probably increased for those who exercise regularly. Although the roles of the additionally required dietary protein and amino acids are likely to be quite different for those who engage in endurance exercise (protein required as an auxiliary fuel source) as opposed to strength exercise (amino acids required as building blocks for muscle development), it appears that both groups likely will benefit from diets containing more protein than the current RDA of 0.8 g · kg−1 · . Strength athletes probably need about 1.4-1.8 g · kg−1 · and endurance athletes about 1.2-1.4 g · kg−1 · .
Caffeine and Performance
Authors: Spriet Lawrence L.
Published: August 2016

Caffeine ingestion (3-9 mg/kg body weight) prior to exercise increases performance during prolonged endurance exercise and short-term intense exercise lasting ~5 min in the laboratory. These results are generally reported in well-trained elite or recreational subjects. However, there is a lack of well-controlled field studies to determine the applicability of laboratory results to the athletic world. Caffeine does not appear to enhance performance during incremental exercise tests lasting 8-20 min and during sprinting lasting less than 90 s, although research examining sprinting is rare. In addition, the mechanisms responsible for any improvement in endurance and short-term exercise have not been clearly established. The ergogenic effects of caffeine are present with urinary caffeine levels that are below the limit of 12 µg/ml allowed by the International Olympic Committee, which raises serious ethical issues regarding the use of caffeine to improve athletic performance. One solution would be to add caffeine to the list of banned substances, thereby requiring athletes to abstain from caffeine ingestion 48-72 hr prior to competition.
The Role of Medium-Chain Triglycerides in Exercise
Authors: Berning Jacqueline R.
Published: August 2016

Studies investigating fat as a fuel for exercise have found that increasing free fatty acids during exercise tends to spare muscle glycogen due to increased utilization of free fatty acids for energy, which in turn can enhance the capacity for endurance exercise. Medium-chain triglycerides do not delay gastric emptying or absorption. They are broken down by lipase in the stomach and duodenum to glycerol and medium-chain fatty acids (MCFA). Since MCFAs are metabolized as quickly as glucose, it has been speculated that they might provide an alternative carbon source for the muscle during prolonged exercise. While the majority of studies investigating the role of medium-chain triglycerides and exercise have found no sparing effect of muscle glycogen after consumption of medium-chain triglycerides, two recent studies have presented conflicting results. This review will investigate the speculated role of medium-chain triglycerides as an alternative fuel source for exercising muscles and will discuss the possibility that medium-chain triglycerides preserve muscle glycogen during exercise,
The Effect of Oral Creatine Monohydrate Supplementation on Running Velocity
Authors: Redondo Diego R. , Dowling Elizabeth A. , Graham Bryan L. , Almada Anthony L. , Williams Melvin H.
Published: August 2016

Creatine supplementation has been shown to augment muscle PCr content and increase the rate of ATP resynthesis. Thus, we hypothesized that creatine supplementation might enhance sprinting performance. Eighteen subjects completed both of two testing sessions (control and postsupplement) 1 week apart, wherein they sprinted three 60-m distance trials that were recorded with videotape. Following the control session, for 7 days, subjects in the treatment group ingested a creatine-glucose mixture, while the placebo group consumed a glucose powder, followed by the postsupplementation session. Velocities of the subjects through three testing zones within the 60-m sprint were calculated from the videotape. Resultant velocities were analyzed using a MANOVA with a2x2x3x3 (Group x Session x Trial x Zone) design. Results indicated that there were no statistically significant main or interaction effects on velocity between groups for session, trial, or zone. These data do not support the hypothesis that supplementary creatine ingestion will enhance velocity during the early or latter segments of a 60-m sprint.
Effect of Oral Creatine Supplementation on Single-Effort Sprint Performance in Elite Swimmers
Authors: Burke Louise M. , Pyne David B. , Telford Richard D.
Published: August 2016

Oral supplementation with creatine monohydrate (Cr.0) has been reported to increase muscle creatine phosphate levels. The aim of the present study was to determine the effect of such supplementation on performance of a single-effort sprint by elite swimmers. Thirty-two elite swimmers (M = 18, F = 14; age = 17-25 years) from the Australian Institute of Sport were tested on two occasions, 1 week apart. Tests performed were 25-m, 50-m, and 100-m maximal effort sprints (electronically timed with dive start, swimmers performing their best stroke), each with approximately 10 min active recovery. A 10-s maximal leg ergometry test was also undertaken. Swimmers were divided into two groups matched for sex, stroke/event, and sprint time over 50 m, and groups were randomly assigned to 5 days of Cr.0 supplementation (4 · day−1 x 5 g Cr.0 + 2 g sucrose, n = 16) or placebo (4 · day−1 x 5 g Poly cose + -2 g sucrose, n = 16) prior to the second trial. Results revealed no significant differences between the group means for sprint times or between 10-s maximal leg ergometry power and work. This study does not support the hypothesis that creatine supplementation enhances single-effort sprint ability of elite swimmers.
Branched-Chain Amino Acid Supplementation during Repeated Prolonged Skiing Exercises at Altitude
Authors: Bigard André X. , Lavier Pierre , Ullmann Lionel , Legrand Hélène , Douce Philippe , Guezennec Charles Y.
Published: August 2016

This study was conducted to test the hypothesis that a branched-chain amino acid (BCAA) supplementation would minimize changes in body composition and alterations in plasma amino acid profile induced by prolonged exercises at altitude. Twenty-four highly trained subjects participated in six successive sessions of ski mountaineering (6-8 hr duration, altitude 2,500-4,100 m). Twelve subjects took a dietary supplement of BCAA (BCAA group) and 12 took a dietary supplement that was 98% carbohydrate (C group). Body weight decreased in C subjects (-2.1%,p < .01), while the body weight loss recorded in the BCAA group was not statistically significant (-1.2%, NS). Changes in body composition that resulted from repeated skiing exercise at altitude were not significantly minimized by BCAA administration. Peak power output recorded during an incremental bicycle exercise decreased in C subjects but did not change significantly in BCAA subjects. Results of this study demonstrate that neither changes in body composition related to the ski mountaineering program nor muscular performance during isometric contraction was significantly affected by BCAA administration.
Effects of Active Warm-Down and Carbohydrate Feeding on Free Fatty Acid Concentrations after Prolonged Submaximal Exercise
Authors: El-Sayed Mahmoud S. , Rattu Angelheart J.M. , Lin Xia , Reilly Thomas
Published: August 2016

We examined the effects of active warm-down (AWD) and carbohydrate ingestion on plasma levels of free fatty acids (FFAs) and glucose changes into recovery following prolonged submaximal exercise. Subjects in Group 1 cycled at 70% of maximal oxygen uptake (); carbohydrate (CHO) or placebo (PLA) was ingested 15 min before and 45 min during exercise. In the AWD experiment, exercise was followed immediately by an AWD and subjects were given a placebo solution. Group 2 subjects consumed CHO or PLA at 75 min during and after exercise at 70% . ANOVA revealed a significant decrease in blood glucose levels only in Group 1, with a concomitant increase in FFA concentrations during exercise in both groups. Carbohydrate ingestion in Groups 1 and 2 significantly decreased the normal response of FFAs during exercise and markedly reduced the normal elevation of FFAs in recovery. AWD following submaximal exercise had no effect on plasma FFA elevations in recovery. These results suggest that carbohydrate ingestion, but not active warm-down, attenuates FFA elevations in recovery.
Free-Living, 24-Hour, and Sleeping Energy Expenditure in Sedentary, Strength-Trained, and Endurance-Trained Men
Authors: Seale James L. , VanZant Robert S. , Conway Joan M.
Published: August 2016

Fifteen adult male volunteers were assigned to sedentary, moderately strength-trained, and moderately endurance-trained groups (5 per group) to determine the effect of exercise training on energy expenditure (EE). Subjects were matched for age, weight, and height. Group appointments were based on activity questionnaires and American College of Sports Medicine standards. Subjects consumed a mixed diet of 40% fat, 20% protein, and 40% carbohydrate at weight maintenance intake for 3 weeks while continuing their exercise training programs. There was no significant difference between groups for 24-hr EE measured in the controlled environment of a room-sized calorimeter. Free-living EE measured with in endurance- and strength-trained groups was significantly higher (19.4% and 35.1%, respectively) than in the sedentary group. Moderate endurance and strength training increased free-living EE but did not affect 24-hr EE when groups followed standardized activity schedules. These results suggest that increased EE caused by moderate exercise training is limited to the energy required to complete the exercise.
Young Adult Exercisers and Nonexercisers Differ in Food Attitudes, Perceived Dietary Changes, and Food Choices
Authors: Georgiou Constance , Betts Nancy , Hoos Terri , Glenn Marty
Published: August 2016

Health experts recommend merging a healthy diet and adequate physical activity into one behavior. This study compared attitudes about foods, recent dietary changes, and food choices of 319 18- to 24-year-olds, who defined themselves as exercisers or nonexercisers. Subjects were recruited by telephone and were mailed questionnaires that asked about factors influencing food selection and changes in intake of high-fat foods. Exercisers considered it more important to eat nutritious foods; ate more nutrient-dense, low-fat foods; and more frequently met the Food Guide Pyramid recommended grain and fruit intakes than nonexercisers. Female exercisers more often perceived foods high in calcium to be fattening and not healthful, and they reported decreasing their intake of high-fat foods more than did female nonexercisers. Some merging of healthy diet and exercise behavior is evident among the young adult exercisers in this study. Nutrition and exercise messages targeted to young women should emphasize low-calorie calcium sources.
Exercise-Induced Oxidative Stress before and after Vitamin C Supplementation
Authors: Alessio Helaine M. , Goldfarb Allan H. , Cao Guohua
Published: August 2016

Vitamin C (ascorbic acid) was supplemented (1 g/day) for 1 day and 2 weeks in the same subjects. Plasma thiobarbituric acid reacting substances (TB ARS) and oxygen radical absorbance capacity (ORAC) before and after 30 min submaximal exercise were measured. Different vitamin C supplementations did not affect resting TB ARS or ORAC. Following 30 min exercise, values for TBARS were 12.6 and 33% above rest with 1 day and 2 weeks of vitamin C supplementation, respectively, compared to 46% higher with placebo. ORAC did not significantly change (11%) after exercise with a placebo, nor when subjects were given vitamin C supplements for 1 day or 2 weeks (4.9% and 5.73%, respectively). TBARS:ORAC, a ratio representing oxidative stress, increased 32% (p < .05) with placebo compared to 5.8 and 25.8% with vitamin C supplements for 1 day and 2 weeks, respectively. It was concluded that exercise-induced oxidative stress was highest when subjects did not supplement with vitamin C compared to either 1 day or 2 weeks of vitamin C supplementation.
Allithiamine Ingestion Does Not Enhance Isokinetic Parameters of Muscle Performance
Authors: Doyle Matthew R. , Webster Michael J. , Erdmann Loran D.
Published: August 2016

The purpose of this study was to investigate the effect of oral allithiamine administration on isokinetic parameters of muscle performance and lactate accumulation prior to, during, and in recovery from isokinetic exercise. A double-blind, counterbalanced, crossover experimental design utilizing aBiodex System 2 Isokinetic Dynamometer was used to test 15 healthy college students. Subjects orally ingested either 1 g · of a thiamin derivative, allithiamine, or a placebo for 5 days and then performed six exercise sets of knee extension and flexion. ANOVA revealed no significant differences between treatment conditions in peak torque, mean peak torque, average power, or total work performed (p > .05). Likewise, lactate accumulation was not significantly different between treatment conditions at any measurement point (p > .05). The absence of significant differences suggests that oral allithiamine administration does not enhance isokinetic parameters of muscle performance or lactate accumulation prior to, during, and following isokinetic exercise.
Increased Energy and Nutrient Intake during Training and Competition Improves Elite Triathletes' Endurance Performance
Authors: Frentsos Jerry A. , Baer Janine T.
Published: August 2016

Dietary habits were evaluated in 6 elite triathletes (4 male, 2 female). Analysis of 7-day diet records showed mean daily energy and carbohydrate intake to be insufficient to support estimated requirements. Mean intakes of vitamins and most minerals exceeded the Recommended Dietary Allowances (RDAs) except zinc and chromium, which did not meet 66% of recommended amounts. Individualized nutrition intervention using the Diabetic Food Exchange System to support performance during training and competition was provided. To improve dietary intake, subjects consumed fortified nutrition supplements (Reliv, Inc.) before and after daily training. Follow-up 7-day diet records showed that average energy intake and percentage of energy from carbohydrate increased, as did intakes of zinc and chromium. Triathletes' performance in a short course triathlon was improved compared to a similar competition completed prior to the nutrition intervention. Following the intervention, triathletes were able to meet recommended daily energy, macronutrient, and micronutrient intakes and improve endurance performance.
Dietary Practices of South African Ultradistance Runners
Authors: Peters Edith M. , Goetzsche Jeni M.
Published: August 2016

Training (T) and prerace (PR) dietary intakes of male and female athletes participating in a 90-km ultramarathon and the usual diets of matched, sedentary controls were investigated using 24-hr dietary records. Supplement use, mean weekly training distance, and race performance times were recorded. Macro- and micronutrient intakes were analyzed using computerized nutritional analysis programs. Total mean energy intake in the T and PR diets of the runners was 10.1 and 12.8 MJ in the men (n = 150) and 7.5 and 9.1 MJ in the women (n = 23). Mean relative contribution of CHO to the runners' total kilojoule intake increased from 50.0 and 49.5% in the T diets to 57.7 (p < .05; n = 153) and 56.4% (p < .05; n = 23) in the PR diets of male and female runners, respectively, and energy-boosting supplements were included in the PR diets of 48% of female and 59% of male runners. Seventy-eightpercent of female and 62% of male runners used vitamin and mineral supplements in their T diets as opposed to 39% of female and 28% of male controls. No statistically significant relationship was found between total kilojoule, CHO, fat, protein, and selected micronutrient intake during the 3 days before the race and performance in the 90-km event in runners of homogenous training status and gender.