Journal of the International Society of Sports Nutrition - Latest Articles

Comparative effects of selected non-caffeinated rehydration sports drinks on short-term performance following moderate dehydration

Peter Snell — 2010-08-22T00:00:00Z

Background: The effect of moderate dehydration and consequent fluid replenishment on short-duration maximal treadmill performance was studied in eight healthy, fit (VO2max = 49.7 +/- 8.7 mL kg-1 min-1) males aged 28 +/- 7.5 yrs. Methods: The study involved a within subject, blinded, crossover, placebo design. Initially, all subjects performed a baseline exercise test using an individualized treadmill protocol structured to induce exhaustion in 7 to 10 min. On each of the three subsequent testing days, the subjects exercised at 70-75% VO2max for 60 min at 29-33degrees C, resulting in a dehydration weight loss of 1.8-2.1% body weight. After 60 min of rest and recovery at 22 C, subjects performed the same treadmill test to voluntary exhaustion, which resulted in a small reduction in VO2max and a decline in treadmill performance by 3% relative to the baseline results. Following another 60 min rest and recovery, subjects ingested the same amount of fluid lost in the form of one of three lemon-flavored, randomly assigned commercial drinks, namely Crystal Light (placebo control), Gatorade(R) and Rehydrate Electrolyte Replacement Drink, and then repeated the treadmill test to voluntary exhaustion. Results: VO2max returned to baseline levels with Rehydrate, while there was only a slight improvement with Gatorade and Crystal Light. There were no changes in heart rate or ventilation with all three different replacement drinks. Relative to the dehydrated state, a 6.5% decrease in treadmill performance time occurred with Crystal Light, while replenishment with Gatorade, which contains fructose, glucose, sodium and potassium, resulted in a 2.1% decrease. In contrast, treatment with Rehydrate, which comprises fructose, glucose polymer, calcium, magnesium, sodium, potassium, amino acids, thiols and vitamins, resulted in a 7.3% increase in treadmill time relative to that of the dehydrated state. Conclusions: The results indicate that constituents other than water, simple transportable monosaccharides and sodium are important for maximal exercise performance and effective recovery associated with endurance exercise-induced dehydration.

Ergogenic effects of betaine supplementation on strength and power performance

Elaine Lee — 2010-07-19T00:00:00Z

Background: We investigated the ergogenic effects of betaine (B) supplementation on strength and power performance. Methods: Twelve men (mean ± SD age, 21 ± 3 yr; mass, 79.1 ± 10.7 kg) with a minimum of 3 months resistance training completed two 14-day experimental trials separated by a 14-day washout period, in a balanced, randomized, double-blind, repeated measures, crossover design. Prior to and following 14 days of twice daily B or placebo (P) supplementation, subjects completed two consecutive days (D1 and D2) of a standardized high intensity strength/power resistance exercise challenge (REC). Performance included bench, squat, and jump tests. Results: Following 14-days of B supplementation, D1 and D2 bench throw power (1779 ± 90 and 1788 ± 34 W, respectively) and isometric bench press force (2922 ± 297 and 2503 ± 28 N, respectively) were increased (p < 0.05) during REC compared to pre-supplementation values (1534 ± 30 and 1498 ± 29 W, respectively; 2345 ± 64 and 2423 ± 84 N, respectively) and corresponding P values (1374 ± 128 and 1523 ± 39 W; 2175 ± 92 and 2128 ± 56 N, respectively). Compared to pre-supplementation, vertical jump power and isometric squat force increased (p < 0.05) on D1 and D2 following B supplementation. However, there were no differences in jump squat power or the number of bench press or squat repetitions. Conclusion: B supplementation increased power, force and maintenance of these measures in selected performance measures, and these were more apparent in the smaller upper-body muscle groups.

Effect of 28 days of creatine ingestion on muscle metabolism and performance of a simulated cycling road race

Robert Hickner — 2010-07-07T00:00:00Z

PurposeThe effects of creatine supplementation on muscle metabolism and exercise performance during a simulated endurance road race was investigated. Methods: Twelve adult male (27.3 ± 1.0 yr, 178.6 ± 1.4 cm, 78.0 ± 2.5 kg, 8.9 ± 1.1 %fat) endurance-trained (53.3 ± 2.0 ml* kg-1* min-1, cycling ~160 km/wk) cyclists completed a simulated road race on a cycle ergometer (Lode), consisting of a two-hour cycling bout at 60% of peak aerobic capacity (VO2peak) with three 10-second sprints performed at 110% VO2 peak every 15 minutes. Cyclists completed the 2-hr cycling bout before and after dietary creatine monohydrate or placebo supplementation (3 g/day for 28 days). Muscle biopsies were taken at rest and five minutes before the end of the two-hour ride. Results: There was a 24.5 ± 10.0% increase in resting muscle total creatine and 38.4 ± 23.9% increase in muscle creatine phosphate in the creatine group (P < 0.05). Plasma glucose, blood lactate, and respiratory exchange ratio during the 2-hour ride, as well as VO2 peak, were not affected by creatine supplementation. Submaximal oxygen consumption near the end of the two-hour ride was decreased by approximately 10% by creatine supplementation (P < 0.05). Changes in plasma volume from pre- to post-supplementation were significantly greater in the creatine group (+14.0 ± 6.3%) than the placebo group (-10.4 ± 4.4%; P < 0.05) at 90 minutes of exercise. The time of the final sprint to exhaustion at the end of the 2-hour cycling bout was not affected by creatine supplementation (creatine pre, 64.4 ± 13.5s; creatine post, 88.8 ± 24.6s; placebo pre, 69.0 ± 24.8s; placebo post 92.8 ± 31.2s: creatine vs. placebo not significant). Power output for the final sprint was increased by ~33% in both groups (creatine vs. placebo not significant). Conclusions: It can be concluded that although creatine supplementation may increase resting muscle total creatine, muscle creatine phosphate, and plasma volume, and may lead to a reduction in oxygen consumption during submaximal exercise, creatine supplementation does not improve sprint performance at the end of endurance cycling exercise.

Potentially fatal new trend in performance enhancement: a cautionary note on nitrite

Andrea Petroczi — 2010-06-29T00:00:00Z

Background: Considerable interest has been shown by athletes and scientists in the potential for nitric oxide and associated vasodilators to enhance performance. This study aims to explore potential misuse of vasodilators by the athletes, and to highlight the growing concern over these agents. Methods: Retrospective analyses of anonymous inquiries recorded in the Drug Information Database™ (DID™) between January 2006 and June 2008 (inclusive). In this 30-month period, the DID™ recorded 198,023 inquiries, of which 118,724 were UK Licensed Pharmaceutical products with a further 79,299 inquiries made for substance not found in the database. Results: Phosphodiesterase type 5 (PDE-5) inhibitors, dominated by Viagra®, ranked 16th among the substance groups. The proportion of the inquiries made regarding PDE-5 inhibitors, especially in comparison to antibiotics, painkillers or alcohol, appears to be above the level that would normally be expected from medical need. No significant change in the months leading up to the Beijing Olympics was observed. On the contrary, the Nitric/Nitrate group showed a notable increase between 2006-2007 and 2008, suggesting a potential increase in interest in using nitric oxide among athletes. Conclusions: With patents recently filed for the use of agents containing sodium nitrite/nitrate to enhance blood flow for performance enhancement in sport, coupled with anecdotal evidence from internet athlete forums and media, there is a concern that athletes may endanger their health by using vasodilators to enhance athletic performance. PDE-5 inhibitors or chemicals in the nitrate/nitrate group are currently not prohibited or tested for by the doping control agencies but some are highly dangerous to health and can lead to cardiovascular collapse, coma and death. Its promotion among athletes as a performance enhancing supplement is ethically and medically questionable.

Prevalence of micronutrient deficiency in popular diet plans

Jayson Calton — 2010-06-10T00:00:00Z

Background: Research has shown micronutrient deficiency to be scientifically linked to a higher risk of overweight/obesity and other dangerous and debilitating diseases. With more than two-thirds of the U.S. population overweight or obese, and research showing that one-third are on a diet at any given time, a need existed to determine whether current popular diet plans could protect followers from micronutrient deficiency by providing the minimum levels of 27 micronutrients, as determined by the U.S. Food and Drug Administrations (FDA) Reference Daily Intake (RDI) guidelines. Methods: Suggested daily menus from four popular diet plans (Atkins for Life diet, The South Beach Diet, the DASH diet, the DASH diet) were evaluated. Calorie and micronutrient content of each ingredient, in each meal, were determined by using food composition data from the U.S. Department of Agriculture Nutrient Database for Standard Reference. The results were evaluated for sufficiency and total calories and deficient micronutrients were identified. The diet plans that did not meet 100% sufficiency by RDI guidelines for each of the 27 micronutrients were re-analyzed; (1) to identify a micronutrient sufficient calorie intake for all 27 micronutrients, and (2) to identify a second micronutrient sufficient calorie intake when consistently low or nonexistent micronutrients were removed from the sufficiency requirement. Results: Analysis determined that each of the four popular diet plans failed to provide minimum RDI sufficiency for all 27 micronutrients analyzed. The four diet plans, on average, were found to be RDI sufficient in (11.75 ± 2.02; mean ± SEM) of the analyzed 27 micronutrients and contain (1748.25 ± 209.57) kcal. Further analysis of the four diets found that an average calorie intake of (27,575 ± 4660.72) would be required to achieve sufficiency in all 27 micronutrients. Six micronutrients (vitamin B7, vitamin D, vitamin E, chromium, iodine and molybdenum) were identified as consistently low or nonexistent in all four diet plans. These six micronutrients were removed from the sufficiency requirement and additional analysis of the four diets was conducted. It was determined that an average calorie content of (3,475 ± 543.81) would be required to reach 100% sufficiency in the remaining 21 micronutrients. Conclusion: These findings are significant and indicate that an individual following a popular diet plan as suggested, with food alone, has a high likelihood of becoming micronutrient deficient; a state shown to be scientifically linked to an increased risk for many dangerous and debilitating health conditions and diseases.

Suppression of exercise-induced neutrophilia and lymphopenia in athletes by cystine/theanine intake: a randomized, double-blind, placebo-controlled trial

Shigeki Murakami — 2010-06-04T00:00:00Z

Background: Intense exercise induces increased blood neutrophil counts and decreased lymphocyte counts, and leads to inflammation and immunosuppression. It was previously reported that cystine and theanine (CT) supplementation by long-distance runners before a training camp suppressed the changes of these blood parameters observed in un-supplemented control subjects after the camp. The purpose of the present study was to determine the effects of CT supplementation on the inflammatory response and immune state before and after intense endurance exercise in long-distance runners at a training camp. Methods: Sixteen long-distance runners were allocated to one of two groups given CT supplements (700 mg cystine + 280 mg theanine daily) or placebo (8 in each group) for 7 days prior to and during a 9-day training camp. Daily run training averaged 19.9 km/day prior to the camp and 28.6 km/day during the camp. On the initial and final days of the camp, blood samples were collected before and after 15 km morning interval running workouts (1000 m × 15 times) and analyzed for neutrophil and lymphocyte counts and myoglobin. Results: The relative change in exercise-induced blood neutrophil count (% of pre-exercise values) was significantly lower in the CT group than in the placebo group (163.3 ± 43.2% vs. 200.4 ± 19.6%, p = 0.044) on the initial day of camp, but not on the last day. The decline in lymphocyte count (% of pre-exercise values) was significantly less in the CT group than in the placebo group (60.2 ± 19.2% vs. 36.2 ± 12.0%, p = 0.010) on the initial day of camp, but not on the last day. In blood myoglobin, there was a trend toward lower % of pre-exercise values in the CT group (p < 0.09) on both measurement days. Conclusion: CT supplementation significantly attenuated the increase in neutrophil count and the reduction in lymphocyte count induced by intense endurance exercise. These results suggest that CT supplementation may suppress the exercise-induced fluctuation of the blood immunocompetent cells and may help to reduce the alteration of the immune state.

Brain serotonergic and dopaminergic modulators, perceptual responses and endurance exercise performance following caffeine co-ingested with a high fat meal in trained humans

Marios Hadjicharalambous — 2010-05-27T00:00:00Z

Background: The present study examined putative modulators and indices of brain serotonergic and dopaminergic function, perceptual responses, and endurance exercise performance following caffeine co-ingested with a high fat meal. Methods: Trained humans (n = 10) performed three constant-load cycling tests at 73% of maximal oxygen uptake (VO2max) until exhaustion at 10°C. Prior to the first test, subjects consumed a 90% carbohydrate meal (Control trial) and for the remaining two tests, a 90% fat meal with (FC trial) and without (F trial) caffeine. Results: Time to exhaustion was not different between the F and FC trials (P > 0.05); [Control trial: 116(88-145) min; F trial: 122(96-144) min; FC trial: 127(107-176) min]. However, leg muscular discomfort during exercise was significantly lower on the FC relative to F trial (P < 0.01). There were no significant differences between F and FC trials in key modulators and indices of brain serotonergic (5-HT) and dopaminergic (DA) function [(i.e. plasma free and total tryptophan (Trp), tyrosine (Tyr), large neutral amino acids (LNAA), Trp:LNAA ratio, free-Trp:Tyr ratio, total Trp:Tyr ratio, and plasma prolactin] (P > 0.05) with the exception of plasma free-Trp:LNAA ratio which was higher at 90 min and at exhaustion during the FC trial (P < 0.05). Conclusions: Neither brain 5-HT nor DA systems would appear to be implicated in the fatigue process when exercise is performed without significant thermoregulatory stress, thus indicating fatigue development during exercise in relatively cold temperatures to occur predominantly due to glycogen depletion.

Vernonia cinerea Less. supplementation and strenuous exercise reduce smoking rate: relation to oxidative stress status and beta-endorphin release in active smokers in Active Smokers

Donrawee Leelarungrayub — 2010-05-26T00:00:00Z

PurposeThe aim of this study was to evaluate the effects of Vernonia cinerea Less. (VC) supplementation and exercise on oxidative stress biomarkers, beta-endorphin release, and the rate of cigarette smoking. Methods: Volunteer smokers were randomly divided into four groups: group 1: VC supplement; group 2: exercise with VC supplement; group 3: exercise; and group 4: control. VC was prepared by wash and dry techniques and taken orally before smoking, matching the frequency of strenuous exercise (three times weekly). Before and after a two month period, exhaled carbon monoxide (CO), blood oxidative stress (malondialdehyde [MDA], nitric oxide [NOx], protein hydroperoxide [PrOOH] and total antioxidant capacity [TAC]), beta-endorphin and smoking rate were measured, and statistically analyzed. Results: In Group 1, MDA, PrOOH, and NOx significantly decreased, whereas TAC increased (p < 0.05). In Group 2, MDA and PrOOH decreased (p < 0.05), with no other changes noted (p > 0.05). In Group 3, MDA, PrOOH, NOx, TAC, and beta-endorphin levels increased significantly (p < 0.05). Group 4 showed no change in oxidative stress variables or beta-endorphine levels (p > 0.05). All groups had lower levels of CO after the intervention. The smoking rate for light cigarette decreased in group 2(62.7%), 1(59.52%), 3 (53.57%) and 4(14.04%), whereas in self-rolled cigarettes it decreased in group 1 (54.47%), 3 (42.30%), 2 (40%) and 4 (9.2%). Conclusion: Supplementation with Vernonia cinerea Less and exercise provided benefit related to reduced smoking rate, which may be related to oxidaive stress and beta-endorphine levels.

Effect of beta-alanine supplementation on the onset of blood lactate accumulation (OBLA) during treadmill running: Pre/post 2 treatment experimental design

Thomas Jordan — 2010-05-19T00:00:00Z

Background: β-Alanine (βA) has been shown to improve performance during cycling. This study was the first to examine the effects of βA supplementation on the onset of blood lactate accumulation (OBLA) during incremental treadmill running. Methods: Seventeen recreationally-active men (mean ± SE 24.9 ± 4.7 yrs, 180.6 ± 8.9 cm, 79.25 ± 9.0 kg) participated in this randomized, double-blind, placebo-controlled pre/post test 2-treatment experimental design. Subjects participated in two incremental treadmill tests before and after 28 days of supplementation with either βA (6.0 g·d-1)(βA, n = 8) or an equivalent dose of Maltodextrin as the Placebo (PL, n = 9). Heart rate, percent heart rate maximum (%HRmax), %VO2max@OBLA (4.0 mmol.L-1 blood lactate concentration) and VO2max (L.min-1) were determined for each treadmill test. Friedman test was used to determine within group differences; and Mann-Whitney was used to determine between group differences for pre and post values (p < 0.05). Results: The βA group experienced a significant rightward shift in HR@OBLA beats.min-1 (p < 0.01) pre/post (161.6 ± 19.2 to 173.6 ± 9.9) but remained unchanged in the PL group (166.8 ± 15.8 to 169.6 ± 16.1). The %HRmax@OBLA increased (p < 0.05) pre/post in the βA group (83.0% ± 9.7 to 88.6% ± 3.7) versus no change in the PL group (86.3 ± % 4.8 to 87.9% ± 7.2). The %VO2max@OBLA increased (p < 0.05) in the βA group pre/post (69.1 ± 11.0 to 75.6 ± 10.7) but remained unchanged in the PL group (73.3 ± 7.3 to 74.3 ± 7.3). VO2max (L.min-1) decreased (p < 0.01) in the βA group pre/post (4.57 ± 0.8 to 4.31 ± 0.8) versus no change in the PL group (4.04 ± 0.7 to 4.18 ± 0.8). Body mass kg increased (p < 0.05) in the βA group pre/post (77.9 ± 9.0 to 78.3 ± 9.3) while the PL group was unchanged (80.6 ± 9.1 to 80.4 ± 9.0). Conclusions: βA supplementation for 28 days enhanced sub-maximal endurance performance by delaying OBLA. However, βA supplemented individuals had a reduced aerobic capacity as evidenced by the decrease in VO2max values post supplementation.

Effects of chocolate milk consumption on markers of muscle recovery following soccer training: a randomized cross-over study

Stephanie Gilson — 2010-05-18T00:00:00Z

Background: The efficacy of chocolate milk (CM) as a recovery beverage following a period of increased training duration (ITD) was studied in intercollegiate soccer players. Methods: 13 subjects completed one week of normal 'baseline' training followed by four days of ITD. After each day of ITD, subjects received either a high-carbohydrate (504 kcal; CHO: 122 g; 2 g Fat) or isocaloric CM (504 kcal; 84 g CHO; 28 g Pro; 7 g Fat) recovery beverage. Serum creatine kinase (CK), myoglobin (Mb), muscle soreness, fatigue ratings and isometric quadriceps force (MVC) were obtained prior to ITD, and following 2- and 4-days of ITD. Performance tests (T-drill, vertical jump) were performed within training sessions. Treatments were administered in a randomly counterbalanced protocol, and subjects repeated the procedures with the alternate beverage following a two-week washout period. Results: Mean daily training time and HR increased (p < 0.05) between baseline training and ITD, with no differences between treatments. No treatment*time effects were observed for Mb, muscle soreness, fatigue ratings and MVC. However, serum CK was significantly lower (p < 0.05) following four days of ITD with CM (316.9 ± 188.3 U·L-1) compared to CHO (431.6 ± 310.8 U·L-1). No treatment differences were observed for the performance tests. Conclusions: Post-exercise CM provided similar muscle recovery responses to an isocaloric CHO beverage during four-days of ITD. Future studies should investigate if the attenuated CK levels observed with CM have functional significance during more demanding periods of training.