International journal of sport nutrition最新文献

The two basic aims of this study were to add to the limited literature concerning Inosine as an ergogenic aid, and to determine the effects of Inosine supplementation over a period of 5 and 10 days, at a dosage of 10,000 mg.d-1 on measures associated with aerobic and anaerobic performance. Seven trained, volunteer male subjects (body mass = 63.0 +/- 8.7 kg, VO2max = 67.9 +/- 3.3 ml.kg-1.min-1) participated in this study. The subjects completed three test sessions, each comprising three tests (5 x 6-s sprint, 30-s sprint, and 20-min time trial). Supplementation was carried out in a random, double-blind manner, and the test sessions were undertaken prior to (Baseline, B), on Day 6, and on Day 11. Blood was sampled prior to supplementation as well as on Days 6 and 11 and was analyzed for uric acid and 2,3 DPG. An analysis of the data indicated no performance benefit of supplementation and no improvement in 2,3 DPG concentration. Uric acid concentration increased significantly after both Days 6 and 11 (p < 0.03 and p < 0.004, respectively). It is concluded that Inosine has no ergogenic effects but may cause possible health problems if taken over long periods of time.

The influences of gender, ethnicity, and sport of varsity athletes on their vitamin/mineral supplementation habits were examined. Subjects included 145 females and 266 males from 22 varsity teams; 80% were Caucasian; 12% African American; and 8% Combined-Other. Over half of the subjects took supplements. Males were more likely than females to give "too expensive" as a reason for not taking supplements, and "improve athletic performance" and "build muscle" as reasons for taking supplements. The most common supplement was multivitamins plus minerals. Females were more likely to take calcium and iron, and males vitamins B12 and A. African Americans were the most likely to take vitamin A. Males were more likely to get supplement information from nutritionists/dietitians and self, and females from family members or friends and physicians or pharmacists. Football players were more likely to get supplement information from nutritionists/dietitians, and males in other sports from coaches/trainers. There were some differences in vitamin/mineral supplement habits of the athletes by gender, ethnicity, and sport.

Claims that ENDUROX enhances performance by altering metabolic responses to exercise were tested. In a double-blind crossover design, 10 male subjects were randomly assigned to consume 400 mg of placebo or 800 mg ENDUROX for 7 days. Cycle ergometry was performed for 30 minutes at 25%, followed by 10 min at 65% of peak oxygen consumption. After a 1-week washout period, subjects performed the identical exercise protocol following 7 days of reciprocal supplemental conditions. Expired gases were collected and analyzed continuously for oxygen consumption, minute ventilation, and respiratory exchange ratio. Heart rate, blood pressure, rating of perceived exertion, blood lactate, and serum glycerol data were also collected at regular intervals. A two-way ANOVA with repeated measures revealed no significant main or interaction effects involving group differences (p > 0.05) between trials for any variable during rest, 25% or 65% (VO2 peak), or recovery. Our findings do not support the ergogenic claims for ENDUROX.

Twelve girls who trained in rowing were examined twice a year for 4 years. Their initial age was 11.7 +/- (SD) 0.2 yrs. Control groups consisted of 13 girls age 11.5 +/- 0.3 yrs and 18 girls age 14.4 +/- 0.3 yrs examined simultaneously with trained girls in the first and last year of the study, respectively. The examination involved basic anthropometry, estimation of sexual maturation (Tanner scale), 2-day food records, measurements of resting metabolic rate, energy expenditure following glucose ingestion (50 g), and determinations of blood glucose and plasma insulin concentrations prior to and 2 hrs after glucose load. Body mass, height, and fat content were slightly greater in trained girls. None of the subjects reported disturbances in menstrual function, and the age of menarche was similar for all. Both trained and untrained girls reported similar daily energy intake closer to the lower limit or slightly below the estimates of energy requirements for adolescents. Resting metabolic rate calculated per kg of total body mass or lean body mass was lower in trained girls, while the thermogenic effect of glucose was greater. Plasma insulin concentrations measured 2 hrs after glucose ingestion were lower in trained girls. The results suggest that in circumpubertal girls, increased physical activity leads to energy conservation at rest in postabsorptive state and a tendency toward enhancement of food-induced thermogenesis.

An excessive use of vitamin/mineral supplements is considered by many to be a common health problem. We surveyed 1,355 adolescent boys and girls attending athletic high schools in Korea for their usage patterns of vitamin/mineral supplements. The usage rate of the vitamin/mineral supplements was 35.8%. The most favored supplements were vitamin C, multivitamins, and calcium. The reasons most cited for taking supplements were "to recover from fatigue," and "to maintain health." Vitamin and mineral intakes occurred over a wide range; mean intake values were typically higher than the Korean RDA. Vitamins B1, B12 and C were consumed in very high amounts at 29.7, 17.9 and 11.1 times the Korean RDA, respectively. When the intakes of nutrients from supplements and diet were combined, it was observed that the intakes of niacin, folic acid, vitamin C, and iron exceeded levels that have been proposed as upper safe limits. The above data underscore the need to provide sound nutritional education to athletic adolescents and their coaches with respect to the use of vitamin/mineral supplements and the links between adequate diet, good health, and physical performance.

Abdominal cramping, nausea, diarrhea, and GI bleeding are often reported in long-distance runners. This study set out to determine the effects of prolonged (2-4 hrs) exercise and NSAID ingestion on gastric and intestinal permeability during the first 5 hrs following the 1996 Chicago Marathon. Thirty-four healthy volunteers (20 M, 14 F; ages 30-50) completed the race and ingested the test solution (5 g sucrose, 5 g lactulose, 2 g rhamnose, in 40 ml water) within 10-15 min. The urinary excretion ratio of lactulose/rhamnose was used to assess small intestine permeability; sucrose excretion was used to evaluate gastric impairment. There were no significant differences for mean training mileage, postrace rectal temperature, and percent dehydration between runners who ingested NSAIDs and those who did not. In all, 75% of subjects reported aspirin or ibuprofen ingestion before or during the race. Runners who ingested ibuprofen had significant elevations in urinary lactulose excretion and lactulose/rhamnose ratio, whereas those who ingested aspirin or who did not ingest either NSAID had no significant differences in urinary excretion of lactulose, rhamnose, sucrose, or lactulose/rhamnose ratio compared to resting controls. Thirteen of the 26 NSAID users and 4 of the 8 non-users reported GI symptoms. It is concluded that (a) ibuprofen but not aspirin ingestion during prolonged exercise may increase gastrointestinal permeability and lead to GI symptoms, and (b) prolonged exercise alone can produce GI symptoms.

This study assessed the nutrient intake, body composition and biochemical indices of National Figure Skating Championship competitors. Four-day diet records, fasting blood samples, and anthropometric measurements were obtained 2 months after the National Championships from 41 figure skaters 11-18 years of age. Energy, carbohydrate, fat, dietary fiber and cholesterol intake were significantly lower compared to the NHANES III averages for adolescents in the U.S. In general, the mean intakes for most vitamins except vitamin D and E were above the recommended intake. But the athletes had lower intakes of vitamin E and B12, and higher intakes of vitamin C, and thiamin (females only) compared with NHANES III. The mean intakes of magnesium, zinc, and iodine by the male skaters were below the recommended levels, as were the mean intakes of calcium, iron, phosphorus, magnesium, and zinc by the female skaters. Also, the number of servings from vegetable, fruit, dairy, and meat groups were below the recommended levels. Biochemical indices of nutritional status were within normal limits for all skaters. But plasma electrolyte concentrations were indicative of potential dehydration status. The results suggest there is a need to develop dietary intervention and educational programs targeted at promoting optimal nutrient and fluid intakes by these athletes to maintain performance and improve long-term health status.

We investigated the effects of carbohydrate ingestion on glycogen replenishment and subsequent short duration, high intensity exercise performance. During Session 1, aerobic power was determined and each subject (N = 6) was familiarized with the 100-kJ cycling test (100KJ-Test). During the treatment sessions, the subjects performed a 100KJ-Test (Ride-1), then consumed 0.7 g.kg body mass-1 of maltodextrin (CHO) or placebo (PLC), rested 60 min, and then performed a second 100KJ-Test (Ride-2). Muscle tissue was collected before (Pre-1) and after Ride-1 (Post-1), and before (Pre-2) and after Ride-2 (Post-2), and analyzed for glycogen concentration. Both treatments yielded a significant increase in glycogen levels following the 60-min recovery, but there was no difference between treatments. Time to complete the 100KJ-Test increased significantly for PLC, but not for CHO. These data indicate that the decrease in performance during Ride-2 in PLC was not the result of a difference in glycogen concentration.

The effect of acute carbohydrate consumption on performance and metabolism of resistance-trained males was determined. Twenty-two subjects, assigned to either carbohydrate (C, n = 8), placebo (P, n = 8), or control (N, n = 6), performed standardized workouts every other day for a week prior to testing and throughout the testing period. Three of these workouts (T1, T2, and T3) were the performance test in that the last bouts of leg extension and bench press were done to failure at 80% of 10 repetition maximum. A carbohydrate or placebo beverage was consumed 30 min prior to T3. Blood samples were drawn before and after T2 and T3. There was no effect of carbohydrate or energy restriction on number of repetitions done during the leg extension performance test. Carbohydrate intake prior to a resistance exercise bout done in negative energy balance state did not affect performance or evidence of muscle damage.

This study assessed the influence of caffeine on metabolic and cardiovascular functions during sustained, light intensity cycling and at rest. Eight healthy, recreationally active adults participated in four randomly assigned, double-blind experimental trials of 60 min upright seated cycle exercise (30% VO2 max) or equivalent rest with caffeine (5 mg.kg-1) or placebo consumed 60 min prior to data collection. Gas exchange was measured by open-circuit spirometry indirect calorimetry. Global blood flow was evaluated by thoracic impedance cardiography and arterial blood pressure by auscultation. A repeated measures ANOVA indicated that pretrial caffeine increased oxygen uptake and energy expenditure rate (p < 0.05) but did not change respiratory exchange ratio. Systolic, diastolic, and mean arterial blood pressure were elevated following caffeine intake (p < 0.05). Cardiac output, heart rate, stroke volume, and systemic vascular resistance were not significantly different between caffeine and placebo sessions. For each of the metabolic and hemodynamic variables examined, the effects of caffeine were similar during constant-load, light intensity cycling and at rest. These data illustrate that caffeine's mild thermogenic influence can be mediated without a major shift in substrate oxidation mixture. Caffeine at this dosage level alters cardiovascular dynamics by augmenting arterial blood pressure.