International journal of sport nutrition最新文献

Sixteen men completed four trials at random as follows: (Trial A) performance of a single bout of resistance exercise preceded by placebo ingestion (vitamin C); (Trial B) ingestion of 1,500 mg L-arginine and 1,500 mg L-lysine, immediately followed by exercise as in Trial A; (Trial C) ingestion of amino acids as in Trial B and no exercise; (Trial D) placebo ingestion and no exercise. Growth hormone (GH) concentrations were higher at 30, 60, and 90 min during the exercise trials (A and B) compared with the resting trials (C and D) (p < .05). No differences were noted in [GH] between the exercise trials. [GH] was significantly elevated during resting conditions 60 min after amino acid ingestion compared with the placebo trial. It was concluded that ingestion of 1,500 mg arginine and 1,500 mg lysine immediately before resistance exercise does not alter exercise-induced changes in [GH] in young men. However, when the same amino acid mixture is ingested under basal conditions, the acute secretion of GH is increased.

Twelve highly trained male runners ran 15 km at self-selected pace on a treadmill in warm conditions to demonstrate differences in physiological responses, fluid preferences, and performance when ingesting sports drinks or plain water before and during exercise. One hour prior to the start of running, an equal volume (1,000 ml) of either water or a 6% or an 8% carbohydrate-electrolyte (CE) drink was ingested. Blood glucose was significantly higher 30 min following ingestion of 6% and 8% CE compared to water, significantly lower at 60 min postingestion with both sports drinks than with water, but similar after 7.5 km of the run for all beverages. During the first 13.4 km, oxygen uptake and run times were not different between trials; however, the final 1.6-km performance run was faster with both CE drinks compared to water. Despite a lower preexercise blood glucose, CE consumption prior to and during exercise significantly improved performance in last 1.6 km of a 15-km run compared to water.

The present study examined the influence of ingesting 3.0 g CHO . kg-1 body mass . 2 hr-1 after prolonged exercise on recovery and running capacity 4 hr later. Nine men and 8 women completed two trials in a counterbalanced design. Each trial consisted of a 90-min run on a level treadmill at 70% VO2 max (R1) followed by 4 hr recovery (REC) and a further exhaustive run at 70% VO2 max (R2). During REC, subjects ingested either two feedings of a 6.9% glucosepolymer (GP) solution (D trial) or two feedings of a 19.3% GP solution (C trial). There were no differences in mean (+/- SE) R2 run times between the C and D trials or between the male and female subjects. More stable blood glucose concentrations were maintained during REC in the C trial, such that blood glucose was elevated in the C trial in comparison with the D trial after 210 min of REC. It was concluded that increasing postexercise carbohydrate intake from 1.0 to 3.0 g CHO . kg-1 body mass . 2 hr-1 does not improve endurance capacity 1 hr later.

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 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.

Vitamin C (ascorbic acid) was supplemented (1 g/day) for 1 day and 2 weeks in the same subjects. Plasma thiobarbituric acid reacting substances (TBARS) and oxygen radical absorbance capacity (ORAC) before and after 30 min submaximal exercise were measured. Different vitamin C supplementations did not affect resting TBARS 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 days (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.

The effects of oral vanadyl sulfate (VOSO4) (0.5 mg/kg/day) on anthropometry, body composition, and performance were investigated in a 12-week, double-blind, placebo-controlled trial involving weight-training volunteers. Performance was assessed in the treatment (VS) and placebo (P) groups using 1 and 10 repetitions maximum (RM) for the bench press and leg extension. Thirty-one subjects completed the trial, with 2 VS subjects withdrawing because of apparent side effects. There were no significant treatment effects for anthropometric parameters and body composition during the trial. Both groups had significant improvements in performance but the only significant effect of treatment was a Treatment x Time interaction in the 1 RM leg extension (p = .002), which could have arisen because the VS group had a lower performance at baseline in this test. It was concluded that oral vanadyl sulfate was ineffective in changing body composition in weight-training athletes, and any modest performance-enhancing effect requires further investigation.

Energy expenditure (EE) was measured at specific steady-state work rates to determine if body fat percentage or gender was associated with exercise EE, substrate oxidation, or work efficiency. Body fat percentage (leaner vs. fatter men, 9-15% vs. 20-25% fat; leaner vs. fatter women, 16-24% vs. 32-48% fat) was not related to work efficiency or submaximal EE. Fatness affected substrate oxidation in men but not in women. Compared to fatter men, leaner men had higher fat oxidation (6.7 +/- 1.6 vs. 1.4 +/- 2.0 mg.kg fat-free mass [FFM]-1.min-1; p < .01) and lower carbohydrate oxidation (26.6 +/- 4.2 vs. 39.3 +/- 5.0 mg.kg FFM-1.min-1; p < .01) at 60% VO2max. When men and women of similar fatness and relative aerobic capacity were compared, men had higher EE measured as kilojoules per minute but similar rates of EE and substrate oxidation per kilogram of FFM at 40-60% VO2max. It was concluded that body FFM, not fatness, is a determinant of exercise EE, whereas fatness is associated with differences in exercise substrate oxidation in men. Along with aerobic fitness, gender and fatness should be considered in future studies of exercise substrate oxidation.

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 2H2(18)O 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.

The purpose of this study was to examine changes in nutrition knowledge, intakes, attitudes, and behaviors as well as health status of 22 female adolescent runners. Subjects completed questionnaires, interviews, and dietary analyses twice over a 3-year period. Over this time they experienced physical growth and improved athletic performance. Although their mean score on a test of basic and sports nutrition knowledge remained stable at 67%, after 3 years more runners correctly responded to statements about carbohydrate and fat. However, fewer responded correctly to statements regarding fluid intake and skipping meals. Although runners increased the percentage of calories consumed as carbohydrates, they significantly decreased their mean energy intake, thus lowering carbohydrate intake. They significantly lowered protein, calcium, potassium, and sodium intakes. The incidence of possible eating disorders increased, as did stress fractures. Over 3 years, nutrition knowledge did not improve, the quality of dietary intakes decreased, incidence of eating disorders and stress fractures increased, and menstrual irregularities remained high.

The purpose of this study was to use the Eating Disorders Inventory-2 (EDI-2) to compare disordered eating pathology between female intercollegiate athletes and a control group of nonathletic subjects enrolled in an advanced program of study. Analysis of variance (ANOVA) procedures revealed no significant difference (NSD) (p > .05) between any of the athletic groups or the control group on any EDI-2 subscale, and there was no significant difference between "lean" sports, other sports, and the control group. There was also NSD on EDI-2 subscale scores on the basis of age. African Americans had significantly lower scores on the Body Dissatisfaction and Impulse Regulation subscales than white Americans. Chi-square analysis revealed NSD between any groups in percentage of respondents scoring above anorexic norms. The results did not indicate a greater amount of disordered eating in female athletes compared to nonathlete controls.