Journal of the International Society of Sports Nutrition - Most accessed articles

ISSN exercise & sports nutrition review: research & recommendations

Richard Kreider — 2010-02-02T00:00:00Z

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.

International Society of Sports Nutrition position stand: creatine supplementation and exercise

Thomas Buford — 2007-08-30T00:00:00Z

Introduction (this article has no abstract)The use of creatine as a sport supplement has been surrounded by both controversy and fallacy since it gained widespread popularity in the early 1990's. Anecdotal and media reports have often claimed that creatine usage is a dangerous and unnecessary practice; often linking creatine use to anabolic steroid abuse. Many athletes and experts in the field have reported that creatine supplementation is not only beneficial for athletic performance and various medical conditions but is also clinically safe. Although creatine has recently been accepted as a safe and useful ergogenic aid, several myths have been purported about creatine supplementation which include:1. All weight gained during supplementation is due to water retention.2. Creatine supplementation causes renal distress.3. Creatine supplementation causes cramping, dehydration, and/or altered electrolyte status.4. Long-term effects of creatine supplementation are completely unknown.5. Newer creatine formulations are more beneficial than creatine monohydrate and cause fewer side effects.6. It's unethical and/or illegal to use creatine supplements.While these myths have been refuted through scientific investigation, the general public is still primarily exposed to the mass media which may or may not have accurate information. Due to this confounding information, combined with the fact that creatine has become one of the most popular nutritional supplements on the market, it is important to examine the primary literature on supplemental creatine ingestion in humans. The purpose of this review is to determine the present state of knowledge concerning creatine supplementation, so that reasonable guidelines may be established and unfounded fears diminished in regard to its use.

Effect of New Zealand blueberry consumption on recovery from eccentric exercise-induced muscle damage

Yanita McLeay — 2012-05-07T00:00:00Z

Background: Exercise-induced muscle damage (EIMD) is accompanied by localized oxidative stress /inflammation which, in the short-term at least, is associated with impaired muscularperformance. Dietary antioxidants have been shown to reduce excessive oxidative stress;however, their effectiveness in facilitating recovery following EIMD is not clear. Blueberriesdemonstrate antioxidant and anti-inflammatory properties. In this study we examine the effectof New Zealand blueberries on EIMD after strenuous eccentric exercise. Methods: In a randomized cross-over design, 10 females consumed a blueberry smoothie or placebo ofa similar antioxidant capacity 5 and 10 hours prior to and then immediately, 12 and 36 hoursafter EIMD induced by 300 strenuous eccentric contractions of the quadriceps. Absolute peakand average peak torque across the knee, during concentric, isometric, and eccentric actionswere measured. Blood biomarkers of oxidative stress, antioxidant capacity, and inflammationwere assessed at 12, 36 and 60 hours post exercise. Data were analyzed using a two-wayANOVA. Results: A significant (p < 0.001) decrease in isometric, concentric and eccentric torque was observed12 hours following exercise in both treatment groups. During the 60 hour recovery period, asignificant (p = 0.047) interaction effect was seen for peak isometric tension suggesting afaster rate of recovery in the blueberry intervention group. A similar trend was observed forconcentric and eccentric strength. An increase in oxidative stress and inflammatorybiomarkers was also observed in both treatment groups following EIMD. Although a fasterrate of decrease in oxidative stress was observed in the blueberry group, it was not significant(p < 0.05) until 36 hours post-exercise and interestingly coincided with a gradual increase inplasma antioxidant capacity, whereas biomarkers for inflammation were still elevated after 60hours recovery. Conclusions: This study demonstrates that the ingestion of a blueberry smoothie prior to and after EIMDaccelerates recovery of muscle peak isometric strength. This effect, although independent ofthe beverage's inherent antioxidant capacity, appears to involve an up-regulation of adaptiveprocesses, i.e. endogenous antioxidant processes, activated by the combined actions of theeccentric exercise and blueberry consumption. These findings may benefit the sportingcommunity who should consider dietary interventions that specifically targets health andperformance adaptation.

Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study

Glyn Howatson — 2012-05-08T00:00:00Z

Background: It is well documented that exercise-induced muscle damage (EIMD) decreases musclefunction and causes soreness and discomfort. Branched-chain amino acid (BCAA)supplementation has been shown to increase protein synthesis and decrease muscle proteinbreakdown, however, the effects of BCAAs on recovery from damaging resistance trainingare unclear. Therefore, the aim of this study was to examine the effects of a BCAAsupplementation on markers of muscle damage elicited via a sport specific bout of damagingexercise in trained volunteers. Methods: Twelve males (mean +/- SD age, 23 +/- 2 y; stature, 178.3 +/- 3.6 cm and body mass, 79.6 +/- 8.4 kg)were randomly assigned to a supplement (n = 6) or placebo (n = 6) group. The damagingexercise consisted of 100 consecutive drop-jumps. Creatine kinase (CK), maximal voluntarycontraction (MVC), muscle soreness (DOMS), vertical jump (VJ), thigh circumference (TC)and calf circumference (CC) were measured as markers of muscle damage. All variables weremeasured immediately before the damaging exercise and at 24, 48, 72 and 96 h post-exercise. Results: A significant time effect was seen for all variables. There were significant group effectsshowing a reduction in CK efflux and muscle soreness in the BCAA group compared to theplacebo (P < 0.05). Furthermore, the recovery of MVC was greater in the BCAA group(P < 0.05). The VJ, TC and CC were not different between groups. Conclusion: The present study has shown that BCAA administered before and following damagingresistance exercise reduces indices of muscle damage and accelerates recovery in resistancetrainedmales. It seems likely that BCAA provided greater bioavailablity of substrate toimprove protein synthesis and thereby the extent of secondary muscle damage associatedwith strenuous resistance exercise. Clinical Trial Registration Number: NCT01529281.

Dose response effects of a caffeine-containing energy drink on muscle performance: a repeated measures design

Juan Del Coso — 2012-05-08T00:00:00Z

Background: Energy drinks have become the most used caffeine-containing beverages in the sport setting.The aim of this study was to determine the effects of two doses of a caffeine-containingenergy drink on muscle performance during upper- and lower-body power-load tests. Methods: In a randomized order, twelve active participants ingested 1 and 3 mg of caffeine per kg ofbody weight using a commercially available energy drink (Fure(R), ProEnergetics) or the samedrink without caffeine (placebo; 0 mg/kg). After sixty minutes, resting metabolic rate, heartrate and blood pressure were determined. Then, half-squat and bench-press power productionwith loads from 10 to 100% of 1 repetition maximum was determined using a rotatorencoder. Results: In comparison to the placebo, the ingestion of the caffeinated drink increased mean arterialpressure (82 +/- 7 < 88 +/- 8 [almost equal to] 90 +/- 6 mmHg for 0 mg/kg, 1 mg/kg, 3 mg/kg of caffeine,respectively; P < 0.05) and heart rate (57 +/- 7 < 59 +/- 8 < 62 +/- 8 beats/min, respectively; P <0.05) at rest in a dose response manner, though it did not affect resting metabolic rate. Whilethe ingestion of 1 mg/kg of caffeine did not affect maximal power during the power-load testswith respect to the placebo, 3 mg/kg increased maximal power in the half-squat (2554 +/- 167[almost equal to] 2549 +/- 161 < 2726 +/- 167 W, respectively; P < 0.05) and bench-press actions (349 +/- 34 [almost equal to]358 +/- 35 < 375 +/- 33 W, respectively; P < 0.05). Conclusions: A caffeine dose of at least 3 mg/kg in the form of an energy drink is necessary to significantlyimprove half-squat and bench-press maximal muscle power.

Beta-hydroxy-beta-methyl-butyrate blunts negative age-related changes in body composition, functionality and myofiber dimensions in rats

Jacob Wilson — 2012-04-18T00:00:00Z

PurposeTo determine the effects of 16 wk. of beta-hydroxy-beta-methylbutyrate (HMB) administration on age-related changes in functionality and diffusion tensor imaging (DTI) determined myofiber dimensions. Methods: Twelve young (44 wk.), 6 middle-aged (60 wk.), 10 old (86 wk.), and 5 very old (102 wk.) male Fisher-344 rat's body composition and grip strength were assessed at baseline. Following, 6 young, 6 middle-aged, 5 old and 5 very old rats were sacrificed for baseline myofiber dimensions and gene transcript factor expression in the soleus (SOL) and gastrocnemius (GAS). The remaining 6 young and 5 old rats were given HMB for 16 wk. and then sacrificed. Results: Fat mass increased in the middle-aged control condition (+49%) but not the middle-aged HMB condition. In addition, fat mass declined (56%) in the old HMB condition but not the old control condition. Normalized strength declined and maintained respectively in the control and HMB conditions from 44 to 60 wk. and increased (+23%) (p < 0.05) from 86 to 102 wk. in only the HMB condition. Declines occurred in myofiber size in all muscles from 44 to 102 wk. in the control condition(10 to 15%), but not HMB condition. Atrogin-1 mRNA expression in the SOL and GAS muscles was greater in the 102-wk control condition than all other conditions: SOL (+45%) and GAS (+100%). This elevation was blunted by HMB in the 102 wk. old SOL. There was a condition effect in the SOL for myogenin, which significantly increased (+40%) only in the 102-wk. HMB group relative to the 44-wk. group. Conclusions: HMB may blunt age-related losses of strength and myofiber dimensions, possibly through attenuating the rise in protein breakdown.

Adenosine 5' -triphosphate (ATP) supplements are not orally bioavailable: a randomized, placebocontrolled cross-over trial in healthy humans

Ilja Arts — 2012-04-17T00:00:00Z

Background: Nutritional supplements designed to increase adenosine 5' -triphosphate (ATP) concentrationsare commonly used by athletes as ergogenic aids. ATP is the primary source of energy for thecells, and supplementation may enhance the ability to maintain high ATP turnover duringhigh-intensity exercise. Oral ATP supplements have beneficial effects in some but not allstudies examining physical performance. One of the remaining questions is whether orallyadministered ATP is bioavailable. We investigated whether acute supplementation with oralATP administered as enteric-coated pellets led to increased concentrations of ATP or itsmetabolites in the circulation. Methods: Eight healthy volunteers participated in a cross-over study. Participants were given in randomorder single doses of 5000 mg ATP or placebo. To prevent degradation of ATP in the acidicenvironment of the stomach, the supplement was administered via two types of pH-sensitive,enteric-coated pellets (targeted at release in the proximal or distal small intestine), or via anaso-duodenal tube. Blood ATP and metabolite concentrations were monitored by HPLC for4.5 h (naso-duodenal tube) or 7 h (pellets) post-administration. Areas under the concentrationvs. time curve were calculated and compared by paired-samples t-tests. Results: ATP concentrations in blood did not increase after ATP supplementation via enteric-coatedpellets or naso-duodenal tube. In contrast, concentrations of the final catabolic product ofATP, uric acid, were significantly increased compared to placebo by ~50% afteradministration via proximal-release pellets (P = 0.003) and naso-duodenal tube (P = 0.001),but not after administration via distal-release pellets. Conclusions: A single dose of orally administered ATP is not bioavailable, and this may explain whyseveral studies did not find ergogenic effects of oral ATP supplementation. On the otherhand, increases in uric acid after release of ATP in the proximal part of the small intestinesuggest that ATP or one of its metabolites is absorbed and metabolized. Uric acid itself mayhave ergogenic effects, but this needs further study. Also, more studies are needed todetermine whether chronic administration of ATP will enhance its oral bioavailability.

Acute L-arginine alpha ketoglutarate supplementation fails to improve muscular performance in resistance trained and untrained men

Benjamin Wax — 2012-04-17T00:00:00Z

Background: Dietary supplements containing L-arginine are marketed to improve exercise performance, but the efficacy of such supplements is not clear. Therefore, this study examined the efficacy of acute ingestion of L-arginine alpha-ketoglutarate (AAKG) muscular strength and endurance in resistance trained and untrained men. Methods: Eight resistance trained and eight untrained healthy males ingested either 3000 mg of AAKG or a placebo 45 minutes prior to a resistance exercise protocol in a randomized, double-blind crossover design. One-repetition maximum (1RM) on the standard barbell bench press and leg press were obtained. Upon determination of 1RM, subjects completed repetitions to failure at 60 % 1RM on both the standard barbell bench press and leg press. Heart rate was measured pre and post exercise. One week later, subjects ingested the other supplement and performed the identical resistance exercise protocol. Results: Our data showed statistical significant differences (p < 0.05) between resistance trained and untrained males for both 1RM and total load volume (TLV; multiply 60 % of 1RM times the number of repetitions to failure) for the upper body. However, 1RM and TLV were not statistically different (p > 0.05) between supplementation conditions for either resistance trained or untrained men in the bench press or leg press exercises. Heart rate was similar at the end of the upper and lower body bouts of resistance exercise with AAKG vs. placebo. Conclusion: The results from our study indicate that acute AAKG supplementation provides no ergogenic benefit on 1RM or TLV as measured by the standard barbell bench press and leg press, regardless of the subjects' training status.

International society of sports nutrition position stand: caffeine and performance

Erica Goldstein — 2010-01-27T00:00:00Z

Position Statement: The position of The Society regarding caffeine supplementation and sport performance is summarized by the following seven points: 1.) Caffeine is effective for enhancing sport performance in trained athletes when consumed in low-to-moderate dosages (~3-6 mg/kg) and overall does not result in further enhancement in performance when consumed in higher dosages (≥ 9 mg/kg). 2.) Caffeine exerts a greater ergogenic effect when consumed in an anhydrous state as compared to coffee. 3.) It has been shown that caffeine can enhance vigilance during bouts of extended exhaustive exercise, as well as periods of sustained sleep deprivation. 4.) Caffeine is ergogenic for sustained maximal endurance exercise, and has been shown to be highly effective for time-trial performance. 5.) Caffeine supplementation is beneficial for high-intensity exercise, including team sports such as soccer and rugby, both of which are categorized by intermittent activity within a period of prolonged duration. 6.) The literature is equivocal when considering the effects of caffeine supplementation on strength-power performance, and additional research in this area is warranted. 7.) The scientific literature does not support caffeine-induced diuresis during exercise, or any harmful change in fluid balance that would negatively affect performance.

International society of sports nutrition position stand: nutrient timing

Chad Kerksick — 2008-10-03T00:00:00Z

Position Statement: The position of the Society regarding nutrient timing and the intake of carbohydrates, proteins, and fats in reference to healthy, exercising individuals is summarized by the following eight points: 1.) Maximal endogenous glycogen stores are best promoted by following a high-glycemic, high-carbohydrate (CHO) diet (600 – 1000 grams CHO or ~8 – 10 g CHO/kg/d), and ingestion of free amino acids and protein (PRO) alone or in combination with CHO before resistance exercise can maximally stimulate protein synthesis. 2.) During exercise, CHO should be consumed at a rate of 30 – 60 grams of CHO/hour in a 6 – 8% CHO solution (8 – 16 fluid ounces) every 10 – 15 minutes. Adding PRO to create a CHO:PRO ratio of 3 – 4:1 may increase endurance performance and maximally promotes glycogen re-synthesis during acute and subsequent bouts of endurance exercise. 3.) Ingesting CHO alone or in combination with PRO during resistance exercise increases muscle glycogen, offsets muscle damage, and facilitates greater training adaptations after either acute or prolonged periods of supplementation with resistance training. 4.) Post-exercise (within 30 minutes) consumption of CHO at high dosages (8 – 10 g CHO/kg/day) have been shown to stimulate muscle glycogen re-synthesis, while adding PRO (0.2 g – 0.5 g PRO/kg/day) to CHO at a ratio of 3 – 4:1 (CHO: PRO) may further enhance glycogen re-synthesis. 5.) Post-exercise ingestion (immediately to 3 h post) of amino acids, primarily essential amino acids, has been shown to stimulate robust increases in muscle protein synthesis, while the addition of CHO may stimulate even greater levels of protein synthesis. Additionally, pre-exercise consumption of a CHO + PRO supplement may result in peak levels of protein synthesis. 6.) During consistent, prolonged resistance training, post-exercise consumption of varying doses of CHO + PRO supplements in varying dosages have been shown to stimulate improvements in strength and body composition when compared to control or placebo conditions. 7.) The addition of creatine (Cr) (0.1 g Cr/kg/day) to a CHO + PRO supplement may facilitate even greater adaptations to resistance training. 8.) Nutrient timing incorporates the use of methodical planning and eating of whole foods, nutrients extracted from food, and other sources. The timing of the energy intake and the ratio of certain ingested macronutrients are likely the attributes which allow for enhanced recovery and tissue repair following high-volume exercise, augmented muscle protein synthesis, and improved mood states when compared with unplanned or traditional strategies of nutrient intake.