ArticlePublisher preview available

Systematic review: Carbohydrate supplementation on exercise performance or capacity of varying durations

Canadian Science Publishing
Applied Physiology Nutrition and Metabolism
Authors:
Trent Stellingwerff at Canadian Sports Institute
Trent Stellingwerff
Gregory R Cox at Bond University
Gregory R Cox
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

This systematic review examines the efficacy of carbohydrate (CHO) supplementation on exercise performance of varying durations. Included studies utilized an all-out or endurance-based exercise protocol (no team-based performance studies) and featured randomized interventions and placebo (water-only) trial for comparison against exclusively CHO trials (no other ingredients). Of the 61 included published performance studies (n = 679 subjects), 82% showed statistically significant performance benefits (n = 50 studies), with 18% showing no change compared with placebo. There was a significant (p = 0.0036) correlative relationship between increasing total exercise time and the subsequent percent increase in performance with CHO intake versus placebo. While not mutually exclusive, the primary mechanism(s) for performance enhancement likely differs depending on the duration of the exercise. In short duration exercise situations (∼1 h), oral receptor exposure to CHO, via either mouthwash or oral consumption (with enough oral contact time), which then stimulates the pleasure and reward centers of the brain, provide a central nervous system-based mechanism for enhanced performance. Thus, the type and (or) amount of CHO and its ability to be absorbed and oxidized appear completely irrelevant to enhancing performance in short duration exercise situations. For longer duration exercise (>2 h), where muscle glycogen stores are stressed, the primary mechanism by which carbohydrate supplementation enhances performance is via high rates of CHO delivery (>90 g/h), resulting in high rates of CHO oxidation. Use of multiple transportable carbohydrates (glucose:fructose) are beneficial in prolonged exercise, although individual recommendations for athletes should be tailored according to each athlete’s individual tolerance.
Figures - available from: Applied Physiology Nutrition and Metabolism
This content is subject to copyright. Terms and conditions apply.
A preview of this full-text is provided by Canadian Science Publishing.
Content available from Applied Physiology Nutrition and Metabolism 
This content is subject to copyright. Terms and conditions apply.
REVIEW
Systematic review: Carbohydrate supplementation on exercise
performance or capacity of varying durations
1
Trent Stellingwerff and Gregory R. Cox
Abstract: This systematic review examines the efficacy of carbohydrate (CHO) supplementation on exercise performance of
varying durations. Included studies utilized an all-out or endurance-based exercise protocol (no team-based performance studies)
and featured randomized interventions and placebo (water-only) trial for comparison against exclusively CHO trials (no other
ingredients). Of the 61 included published performance studies (n= 679 subjects), 82% showed statistically significant perfor-
mance benefits (n= 50 studies), with 18% showing no change compared with placebo. There was a significant (p= 0.0036)
correlative relationship between increasing total exercise time and the subsequent percent increase in performance with CHO
intake versus placebo. While not mutually exclusive, the primary mechanism(s) for performance enhancement likely differs
depending on the duration of the exercise. In short duration exercise situations (⬃1 h), oral receptor exposure to CHO, via either
mouthwash or oral consumption (with enough oral contact time), which then stimulates the pleasure and reward centers of the
brain, provide a central nervous system-based mechanism for enhanced performance. Thus, the type and (or) amount of CHO and
its ability to be absorbed and oxidized appear completely irrelevant to enhancing performance in short duration exercise
situations. For longer duration exercise (>2 h), where muscle glycogen stores are stressed, the primary mechanism by which
carbohydrate supplementation enhances performance is via high rates of CHO delivery (>90 g/h), resulting in high rates of CHO
oxidation. Use of multiple transportable carbohydrates (glucose:fructose) are beneficial in prolonged exercise, although indi-
vidual recommendations for athletes should be tailored according to each athlete’s individual tolerance.
Key words: carbohydrate, performance, duration, dose–response.
Résumé : Cette analyse documentaire systématique scrute l’efficacité de la supplémentation en hydrates de carbone (« CHO ») sur la
performance physique de durée diverse. Les études retenues traitent d’effort a
`fond de train ou d’endurance (pas d’études sur la
performance en équipe) et regroupent des approches aléatoires et des essais avec placebo (eau seulement) a
`des fins de comparaison
avec des essais sur les CHO seulement (pas d’autres ingrédients). Parmi les 61 études sur la performance (n= 679 sujets), 82 % révèlent
des gains de performance statistiquement significatifs (50 études) et 18 % ne révèlent aucune différence avec des groupes placebo. On
note une corrélation significative (p= 0,0036) entre l’augmentation du temps total d’exercice et l’augmentation (%) subséquente de
performance en présence de consommation de CHO comparativement a
`un placebo. Tout en n’étant pas mutuellement exclusifs, les
principaux mécanismes d’amélioration de la performance diffèrent en fonction de la durée de l’exercice. Dans le cas des exercices de
courte durée (⬃1 h), les récepteurs buccaux sont exposés aux CHO, au moyen de rince-bouche ou de la consommation per os (avec
suffisamment de temps de présence en bouche) stimulant ainsi les centres nerveux du plaisir et de la récompense; cette exposition
constitue un mécanisme du système nerveux central pour l’amélioration de la performance. Par conséquent, la nature et/ou la
quantité de CHO pouvant être absorbés et oxydés n’a apparemment rien a
`voir avec l’augmentation de la performance dans les
exercices de courte durée. Dans le cas des exercices de plus longue durée (>2 h) qui grèvent les réserves de glycogène musculaire, les
principaux mécanismes d’amélioration de la performance consécutive a
`la supplémentation en sucres comportent un haut taux
d’approvisionnement en CHO (>90 g/h) suivi d’un haut taux d’oxydation des CHO. L’utilisation de multiples CHO transportables
(glucose:fructose) est bénéfique pour les exercices prolongés, mais les recommandations a
`l’intention des athlètes doivent être
ajustées a
`la capacité de tolérance individuelle. [Traduit par la Rédaction]
Mots-clés : sucres, performance, durée, dose–réponse.
Introduction/approach
Beyond an individual athlete’s genetic trainability and optimized
training program, perhaps the largest single determinant of ensur-
ing optimal performance during prolonged endurance events is
through the intake of carbohydrate (CHO) and fluid. As endorsed by
the 2007 American College of Sports Medicine Exercise and Fluid
Replacement Position Stand (Sawka et al. 2007), it is clear that most
studies show an improvement in endurance performance or capac-
ity when subjects consume a CHO fluid as compared with water
alone (Jeukendrup 2010). Furthermore, a recent meta-analysis on the
performance effect sizes of CHO stated: “Carbohydrate supplements
with an appropriate composition and administration regimen can
have large benefits on endurance performance” (Vandenbogaerde
and Hopkins 2011). However, no recent reviews have examined and
analyzed both the performance magnitude of CHO intake on
either exercise capacity or performance coupled with the mecha-
nistic interpretation and practical recommendations from short
duration CHO mouthwash studies to prolonged (>2 h) exercise
interventions.
Received 30 January 2014. Accepted 17 March 2014.
T. Stellingwerff. Canadian Sport Institute – Pacific, 4371 Interurban Road, Victoria, BC V9E 2C5, Canada.
G.R. Cox. Australian Institute of Sport, Gold Coast, Queensland, Australia.
Corresponding author: Trent Stellingwerff (e-mail: tstellingwerff@csipacific.ca).
1
This paper is a part of a Special Issue entitled Nutritional Triggers to Adaptation and Performance.
998
Appl. Physiol. Nutr. Metab. 39: 998–1011 (2014) dx.doi.org/10.1139/apnm-2014-0027 Published at www.nrcresearchpress.com/apnm on 25 March 2014.
... Ingestion of carbohydrates during exercise is a common practice among athletes, particularly during activities lasting more than 2 hours. Carbohydrate supplementation has been shown to enhance performance [1]; however, intakes above tolerance levels may result in exercise-associated gastrointestinal symptoms (Ex-GIS) which can impair performance [2]. Gut-training is a strategy that may help improve the ability to cope with greater feeding rates during exercise, increasing tolerance and reducing the severity of Ex-GIS [3]. ...
Feeding Tolerance to a Running Gut-Challenge Protocol: a Cross-Sectional Exploration
Article
  • Apr 2025
  • INT J SPORTS MED
This study examined gastrointestinal function, substrate utilization, and exercise performance differences in response to a gut-challenge between (1) female and male athletes, (2) young adult versus masters athletes, and (3) athletes with or without exercise-associated gastrointestinal symptom history (Ex-GIS). Fifty-three endurance athletes (43 males and 10 females) completed a gut-challenge involving a 2-hour run (60% V̇O2max) with 90 g/h carbohydrate intake, followed by a 1-hour self-paced distance test (DT) with ad libitum water. Blood and breath samples were collected pre- and post-exercise. Blood glucose and substrate utilization during exercise were measured, while Ex-GIS and feeding tolerance were assessed pre-, during, and post-exercise. Interest in food and appetite during exercise was lower in symptomatic athletes than asymptomatic athletes (p<0.05). Females had a higher blood glucose concentration during exercise (p=0.037) and immediately after exercise (p=0.003) and a lower whole-body fat oxidation rate during exercise (p=0.009). Exercise performance did not differ based on the biological sex, age, and Ex-GIS history. Overall, gastrointestinal functional markers were comparable between groups, while feeding tolerance and substrate availability and utilization appear to be influenced by the Ex-GIS history and biological sex, respectively. Tailored management of gastrointestinal issues in athletes should be based on an individual basis as opposed to general demographic characteristics.
View
... Glucose and fatty acids are the main energy sources during exercise, with their oxidation rates affected by exercise intensity, duration, and substrate availability. Consuming carbohydrates during extended moderate-to high-intensity exercise is known to boost performance (8)(9)(10). Ingestion of glucose typically results in a peak rate of external carbohydrate oxidation of approximately 1 gram/minute (11,12). ...
Comparing the Effects of Glucose-Fructose versus Glucose on the Oxidation Rate: A Systematic Review and Meta- Analysis
Article
Full-text available
  • Apr 2025
Background Numerous studies have aimed to compare the effects of glucose (Glu) consumption with those of glucose-fructose (Glu-Fru) consumption on oxidation rates during exercise. However, divergent outcomes have surfaced due to variations in exercise protocols and concurrent substance ingestion, leading to a lack of consensus. This systematic review and meta-analysis investigated the comparative effects of Glu and Glu-Fru on total carbohydrate oxidation, endogenous carbohydrate oxidation, exogenous carbohydrate oxidation, and total fat oxidation rates during exercise. Methods A systematic search of PubMed, Scopus, and Web of Science databases up to February 2023. The search yielded 14 randomized controlled trials involving 125 endurance athletes. Results The meta-analyses revealed that Glu supplementation significantly increased total carbohydrate oxidation (WMD: 0.21 g/min) compared to Glu-Fru. Endogenous carbohydrate oxidation significantly increased with Glu (WMD: −0.12), while Glu-Fru led to increased exogenous carbohydrate oxidation (WMD: 0.27 g/min). Total fat oxidation decreased with Glu-Fru (WMD: −0.06 g/min). Conclusion By investigating athletic nutrition complexities, our findings shed light on metabolic responses to Glu-Fru versus Glu supplementation. Tailoring hydration strategies, athletes should select an optimal Glu-Fru to Glu ratio for maximal oxidation and enhanced performance. Future research could explore dose-response relationships for optimal metabolic benefits during exercise.
View
... When evaluating the effects of these products on performance, their positive impacts have been explained by two mechanisms. The first is the provision of carbohydrates, the primary energy source for muscles, which supports the continuous replenishment of glycogen stores, thereby contributing to the energy intake necessary for exercise and metabolism Stellingwerff & Cox, 2014). The second mechanism explains that carbohydrates delay fatigue perception by stimulating the reward center in the brain and the central nervous system (Jeukendrup, 2013;Burke & Maughan, 2015). ...
View
... The phase with the most adequate nutritional control was during the trials (mean score 1.1 ± 1.3) where 23 studies sufficiently controlled the nutrition. Nutrition and especially carbohydrate intake undoubtedly plays a crucial role in prolonged endurance events (Podlogar and Wallis 2022) and has been shown to directly affect time to task failure and/or performance with nutrition in days leading to the exercise bout Bergström et al. 1967), on the day of the bout (Aird et al. 2018) and during the exercise bout (Stellingwerff and Cox 2014). Therefore, adequate nutritional control regarding carbohydrate intake is required to minimise variability in performance due to fatigue derived from low carbohydrate availability, unless the experimental objective is to directly assess the impact of carbohydrate availability on fatigue resistance. ...
What is a cycling race simulation anyway: a review on protocols to assess durability in cycling
Article
Full-text available
  • Feb 2025
  • EUR J APPL PHYSIOL
Physiological resilience or durability is now recognised as a determinant of endurance performance such as road cycling. Reliable, ecologically valid and standardised performance tests in laboratory-based cycling protocols have to be established to investigate mechanisms underpinning, and interventions improving durability. This review aims to provide an overview of available race simulation protocols in the literature and examines its rigour around themes that influence durability including (i) exercise intensity anchoring and (ii) carbohydrate intake whilst also (iii) inspecting reliability and justification of the developed protocols. Using a systematic search approach, 48 articles were identified that met our criteria as a cycling race simulation. Most protocols presented limitations to be recommended as exercise test to investigate durability, such as not appropriately addressing the influence of exercise intensity domains by anchoring exercise intensity as % peak power or % V˙\dot{\text{V}} O2max. Ten articles provided reliability data, but only one articles under the appropriate conditions. Most studies sufficiently controlled nutrition during trials but not in the days leading to the trials or just before the trials. Thus, there is a paucity in protocols that combine justification and reliability with optimal nutritional support and mimic the true demands of a road-cycling race. This review lists an overview of protocols that researchers could use with caution to select a protocol for future experiments, but encourages further development of improved protocols, including utilisation of virtual software applications.
View
... Glucose availability and subsequent skeletal muscle uptake influence performance (Stellingwerff & Cox, 2014). This study found that 7 days of a repetitive feeding-challenge with fat when compared with CHO had no impact on whole-body CHO oxidation. ...
Repetitive Feeding-Challenge With Different Nutritional Densities on Markers of Gastrointestinal Function, Substrate Oxidation, and Endurance Exercise Performance
Article
  • Feb 2025
  • INT J SPORT NUTR EXE
Gut-training has been shown to improve gastrointestinal tolerance, circulatory glucose availability, and exercise performance. The study aimed to investigate the effects of a repetitive feeding-challenge using fat versus carbohydrate (CHO) on markers of gastrointestinal function, glucose availability, and subsequent performance when challenged with a high-CHO load (87 g/hr) during exercise. Forty-four endurance athletes (mean ± SD [9 females and 35 males]: body mass: 71.2 ± 9.2 kg, height: 173.6 ± 7.0 cm, : 55.0 ± 6.1 ml·kg ⁻¹ ·min ⁻¹ ) completed a preintervention gut-challenge trial (T1), involving a 2 hr run (60% ) while taking a CHO gel every 20 min (87 g/hr, 10% w/v ), followed by a 1 hr self-paced distance test with ad libitum water. Participants were then randomized to a fat (fat feeding-challenge [FFC]; 20 g nut butter, 124 kcal, 11 g fat, 3 g protein, and 3 g CHO) or CHO supplement (CHO feeding-challenge [CFC]; 47 g CHO gel: 123 kcal, 29 g CHO) group to complete a 7-day repetitive feeding-challenge (1 hr exercise and supplement intake every 20 min with 290 ml water), followed by a gut-challenge retrial (T2). FFC did not differ from CFC in terms of resting orocecal transit time, feeding tolerance, or substrate oxidation during T1 and T2. Peak breath hydrogen was lower in FFC than CFC ( p = .028) at T2. Total (FFC: 27%, p = .005 vs. CFC: 38%, p = .001) and upper gastrointestinal symptoms severity (FFC: 26%, p = .013 vs. CFC: 40%, p < .001) during exercise was reduced similarly between groups from T1 to T2. FFC covered more distance in T2 (11.51 ± 2.02 vs. 11.08 ± 2.02 km, p = .013), but not significantly different to CFC ( p = . 341). A repetitive feeding-challenge with fat does not enhance nor worsen gastrointestinal and fueling outcomes compared with a CHO repetitive feeding-challenge.
View
... To support physical performance when exercise is initiated with low glycogen availability, the current performance nutrition recommendation is to consume carbohydrate before and during prolonged aerobic exercise (1). Carbohydrate supplementation before and during aerobic exercise provides exogenous substrate for oxidation to sustain physical performance (13). However, the potential ergogenic effects of supplemental carbohydrate may be limited when aerobic exercise is performed in an energy deficit state (14). ...
Carbohydrate supplementation maintains physical performance during short-term energy deficit despite reductions in exogenous glucose oxidation
Article
  • Jan 2025
  • AM J PHYSIOL-ENDOC M
Exogenous glucose oxidation is reduced 55% during aerobic exercise after three days of complete starvation. Whether energy deficits more commonly experienced by athletes and military personnel similarly affect exogenous glucose oxidation and what impact this has on physical performance remains undetermined. This randomized, longitudinal parallel study aimed to assess the effects of varying magnitudes of energy deficit (DEF) on exogenous glucoseoxidation and physical performance compared to energy balance (BAL). Participants consumed a4-day BAL diet, followed by a 6-day 20% ( n=10), 40% ( n=10), or 60% ( n=10) DEF diet. At the end of each energy phase participants performed 90-min of steady-state cycle ergometry (56±3% V̇O 2peak ) while consuming a glucose drink (80 g), followed by a time to exhaustion (TTE) performance test. Substrate oxidation (g/min) was determined by indirect calorimetry and ¹³ C glucose. Muscle glycogen (mmol/kg dry weight) and transcript accumulation were assessed in rested fasted muscle collected before exercise in each phase. Muscle glycogen was lower ( P = 0.002) during DEF (365±179) than BAL (456±125), regardless of group. Transcriptional regulation of glucose uptake ( GLUT4italic> and IRS2) and glycogenolysis ( HKII and PKM) were lower ( P < 0.05) during DEF than BAL, independent of group. Regardless of group, exogenous glucose oxidation was 10% lower ( P < 0.001) during DEF (0.38±0.08) than BAL (0.42±0.08). There was no evidence of a difference in TTE between BAL and DEF or between groups. In conclusion, despite modest reduction in exogenous glucose oxidative capacity during energy deficit, physical performance was similar compared with balance.
View
View
View
Formulation and Development of Spirulina Enriched High Protein Bars for Athletes
Article
  • Jun 2024
  • Indian J Nutr Diet
An athlete requires physical strength, agility, and stamina, and protein is a crucial factor for assessing sports performance. Athletes, marathon runners, and body builders need a higher protein intake of up to 1.5 to 2 gm/kg/day, depending on age and activity level. 20 to 30% of calorie intake should be proteins. The aim of the study is to formulate and develop protein bars infused with functional foods like spirulina, which will be high in protein, targeted at the sportsperson or athletes to meet their requirements. 5 spirulina-based protein bar combinations were created using high-protein and high-fibre ingredients such as whey protein isolate, inulin, and erythritol. Each serving of the protein bars ranged from 50-80 g, providing 15%-30% of energy from protein, at least 3-5 g of fibre, and 1-2 g of spirulina. The recipes varied with sesame seeds, flax seeds, chia seeds, puffed rice, and almonds. The protein bars underwent standardisation in three phases. A semi-trained panel of nutrition experts evaluated the bars using a 9-point hedonic rating scale in each phase, and recipe modifications were made accordingly. In phase 3, the chocolate-coated almond protein bar was deemed the most acceptable and underwent shelf life evaluation, chemical, physical, and microbiological analysis, with data analysed using SPSS version 20. In Phase 1, five energy bars were evaluated for taste, texture, and color, with S-E receiving the highest mean taste rating, followed by S-A, S-D, S-B, and S-C. Overall, S-A, S-D, and S-E were found to be the most acceptable. In Phase 2, S-C (Spirulina + Almonds) was rated highest in taste and texture, making it the best option in terms of overall acceptability. However, S-A had the best color. From all three phases of sensory evaluation, S-A (Spirulina + Almonds - chocolate coated) had the highest mean score for all four sensory attributes, with a ranking scale score also the highest. The protein bar showed no major changes during the 30-day shelf-life analysis, and the taste was acceptable. In Phase 1, five energy bars were evaluated for taste, texture, and color, with S-E receiving the highest mean taste rating, followed by S-A, S-D, S-B, and S-C. Overall, S-A, S-D, and S-E were found to be the most acceptable. In Phase 2, S-C (Spirulina + Almonds) was rated highest in taste and texture, making it the best option in terms of overall acceptability. However, S-A had the best color. From all three phases of sensory evaluation, S-A (Spirulina + Almonds - chocolate coated) had the highest mean score for all four sensory attributes, with a ranking scale score also the highest. The protein bar showed no major changes during the 30-day shelf-life analysis, and the taste was acceptable.
View
A Warm Environment Reduces Exogenous Glucose Oxidation and Endurance Performance during Cycling with Facing Airflow
Article
  • Dec 2024
  • MED SCI SPORT EXER
Exercise in warm environments increases thermal/cardiovascular strain and decreases gastrointestinal (GI) integrity and endurance performance. However, laboratory-based studies have provided little to/no facing airflow, potentially exacerbating these effects, particularly for cycling, where convective cooling may be a major contributor to thermal balance. Purpose This study investigated the effect of cycling in a warm vs temperate environment with sufficient facing airflow on exogenous glucose use, performance, and GI responses. Methods Ten trained male cyclists/triathletes (36 ± 6 y; 55 ± 6 mL/kg/min) completed V̇ O 2peak and familiarisation trials, and two experimental trials in 19 °C (TEMP) and 32 °C (WARM). Experimental trials involved 2 h cycling at ~50% W peak (preload) and an ~15 min time trial (TT) with fan-provided airflow covering the cyclist (preload: ~29 km/h, TT: ~35 km/h). A glucose drink containing [U- ¹³ C]-glucose was consumed every 20 min during the preload (72 g/h). Results Average 40-120 min (TEMP 0.56 ± 0.13 g/min; WARM 0.48 ± 0.12 g/min; 15%; P = 0.015) and peak (TEMP 0.79 ± 0.18 g/min; WARM 0.68 ± 0.14 g/min; 14%; P = 0.008) exogenous glucose oxidation were reduced in WARM. TT performance was 15% slower in WARM (TEMP 819 ± 47 s; WARM 961 ± 130 s; P = 0.002). GI temperature ( P = 0.007), heart rate ( P < 0.001), and RPE ( P = 0.046) were greater during WARM. GI comfort ( P = 0.659) and Intestinal Fatty Acid Binding Protein (IFABP) ( P = 0.094) were not different between trials. Conclusions These data demonstrate that ability to use glucose provided in drinks was impaired during prolonged cycling in WARM. WARM ambient conditions impaired laboratory-based cycling performance, even with facing airflow approximating outdoor conditions, likely via impairments of thermoregulatory, cardiovascular, and metabolic function.
View
Mouth rinsing with a carbohydrate solution does not influence cycle time trial performance in the heat
Article
Full-text available
  • Dec 2013
Ten endurance-trained males were recruited to examine the possible role of carbohydrate (CHO) receptors in the mouth influencing exercise performance in the heat. Volunteers completed an incremental test to exhaustion to determine peak oxygen uptake, a familiarisation trial, followed by 2 experimental trials. Trials consisted of a 1-h time trial undertaken in a climatic chamber maintained at 30 °C, 60% relative humidity. Immediately before, and at regular intervals throughout exercise, subjects ingested a bolus of water and then were provided with either a placebo (PLA) or a 6.4% glucose (CHO) solution to rinse in the mouth for 10 s before being expectorated. There was no difference in total work done between the PLA and CHO trials (758.8 ± 149.0 kJ; 762.6 ± 141.1 kJ; P = 0.951). Pacing was also similar, with no differences in power output apparent during the experimental trials (P = 0.546). Core temperature (P = 0.615), heart rate (P = 0.505), ratings of perceived exertion (P = 0.181), and perceived thermal stress (P = 0.416) were not influenced by the nature of the intervention. Blood glucose concentrations were similar during the CHO and PLA trials (P = 0.117). In contrast to the findings of several studies undertaken in temperate conditions, the present investigation failed to support role of oral sensing of CHO in influencing performance during prolonged exercise in warm conditions.
View
Single and combined effects of beetroot juice and caffeine supplementation on cycling time trial performance
Article
Full-text available
  • Oct 2013
Both caffeine and beetroot juice have ergogenic effects on endurance cycling performance. We investigated whether there is an additive effect of these supplements on the performance of a cycling time trial (TT) simulating the 2012 London Olympic Games course. Twelve male and 12 female competitive cyclists each completed 4 experimental trials in a double-blind Latin square design. Trials were undertaken with a caffeinated gum (CAFF) (3 mg·kg⁻¹ body mass (BM), 40 min prior to the TT), concentrated beetroot juice supplementation (BJ) (8.4 mmol of nitrate (NO3–), 2 h prior to the TT), caffeine plus beetroot juice (CAFF+BJ), or a control (CONT). Subjects completed the TT (females: 29.35 km; males: 43.83 km) on a laboratory cycle ergometer under conditions of best practice nutrition: following a carbohydrate-rich pre-event meal, with the ingestion of a carbohydrate–electrolyte drink and regular oral carbohydrate contact during the TT. Compared with CONT, power output was significantly enhanced after CAFF+BJ and CAFF (3.0% and 3.9%, respectively, p < 0.01). There was no effect of BJ supplementation when used alone (–0.4%, p = 0.6 compared with CONT) or when combined with caffeine (–0.9%, p = 0.4 compared with CAFF). We conclude that caffeine (3 mg·kg⁻¹ BM) administered in the form of a caffeinated gum increased cycling TT performance lasting ∼50–60 min by ∼3%–4% in both males and females. Beetroot juice supplementation was not ergogenic under the conditions of this study.
View
Effects of vitamin E supplementation on exercise-induced oxidative stress: a meta-analysis
Article
Full-text available
  • May 2014
Tocopherols (commonly referred to as “vitamin E”) are frequently studied antioxidants in exercise research. However, the studies are highly heterogeneous, which has resulted in contradicting opinions. The aim of this review is to identify similar studies investigating the effects of tocopherol supplementation on exercise performance and oxidative stress and to perform minimally biased qualitative comparisons and meta-analysis. The literature search and study selection were performed according to Cochrane guidelines. A 2-dimensional study execution process was developed to enable selection of similar and comparable studies. Twenty relevant studies were identified. The high variability of study designs resulted in final selection of 6 maximally relevant studies. Markers of lipid peroxidation (malondialdehyde) and muscle damage (creatine kinase) were the 2 most frequently and similarly measured variables. Meta comparison showed that tocopherol supplementation did not result in significant protection against either exercise-induced lipid peroxidation or muscle damage. The complex antioxidant nature of tocopherols and low accumulation rates in muscle tissues could underlie an absence of protective effects.
View
Bovine colostrum, training status, and gastrointestinal permeability during exercise in the heat: a placebo-controlled double-blind study
Article
Full-text available
  • Jun 2014
Heat stress can increase gastrointestinal permeability, allowing ingress of gram-negative bacterial fragments and thus potentially inflammation and ultimately endotoxemia. Permeability may rise with intense exercise, yet some data indicate that endotoxemia may be mitigated with bovine colostrum supplementation. Using a double-blind, randomised, placebo-controlled crossover study, we tested whether bovine colostrum (COL; 1.7 g·kg⁻¹·day⁻¹ for 7 days) would attenuate physiological strain and aid exercise capacity in the heat, especially in untrained individuals. Seven trained men (T; peak oxygen uptake 64 ± 4 mL·kg⁻¹·min⁻¹) and 8 untrained men (UT, peak oxygen uptake 46 ± 4 mL·kg⁻¹·min⁻¹) exercised for 90 min in 30 °C (50 % relative humidity) after COL or placebo (corn flour). Exercise consisted of 15-min cycling at 50 % heart rate reserve (HRR) before and after 60 min of running (30 min at 80 % HRR then 30-min distance trial). Heart rate, blood pressure (Finometer), esophageal, and skin temperatures were recorded continuously. Gastrointestinal permeability was assessed from urine (double-sugar model, using high-performance liquid chromatography) and blood (intestinal fatty acid-binding protein, I-FABP). The T group ran ∼2.4 km (35%) further than the UT group in the distance trial, and I-FABP increased more in the T group than in the UT group, but physiological and performance outcomes were unaffected by colostrum supplementation, irrespective of fitness. Circulating pro- and anti-inflammatory cytokine concentrations were higher following exercise, but were not modulated by fitness or COL. Despite substantial thermal and cardiovascular strain incurred in environmental conditions in which exertional endotoxemia may occur, bovine colostrum supplementation had no observable benefit on the physiology or performance of either highly trained endurance athletes or untrained individuals.
View
Influence of dietary nitrate on the physiological determinants of exercise performance: a critical review
Article
Full-text available
  • Apr 2014
Dietary nitrate supplementation, usually in the form of beetroot juice, has been heralded as a possible new ergogenic aid for sport and exercise performance. Early studies in recreationally active participants indicated that nitrate ingestion significantly reduces the O2 cost of submaximal exercise and improves performance during high-intensity endurance exercise. Subsequent studies have begun to address the physiological mechanisms underpinning these observations and to investigate the human populations in whom, and the exercise conditions (high- vs. low-intensity, long- vs. short-duration, continuous vs. intermittent, normoxic vs. hypoxic) under which, nitrate supplementation may be beneficial. Moreover, the optimal nitrate loading regimen in terms of nitrate dose and duration of supplementation has been explored. Depending on these factors, nitrate supplementation has been shown to exert physiological effects that could be conducive to exercise performance enhancement, at least in recreationally active or sub-élite athletes. This article provides a “state-of-the-art” review of the literature pertinent to the evaluation of the efficacy of nitrate supplementation in altering the physiological determinants of sport and exercise performance.
View
Variable effects of 12 weeks of omega-3 supplementation on resting skeletal muscle metabolism
Article
Full-text available
  • Apr 2014
Omega-3 supplementation has been purported to improve the function of several organs in the body, including reports of increased resting metabolic rate (RMR) and reliance on fat oxidation. However, the potential for omega-3s to modulate human skeletal muscle metabolism has received little attention. This study examined the effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation on whole-body RMR and the content of proteins involved in fat metabolism in human skeletal muscle. Recreationally active males supplemented with 3.0 g/day of EPA and DHA (n = 21) or olive oil (n = 9) for 12 weeks. Resting muscle biopsies were sampled in a subset of 10 subjects before (pre) and after (post) omega-3 supplementation. RMR significantly increased (5.3%, p = 0.040) following omega-3 supplementation (Pre, 1.33 ±0.05; Post, 1.40 ±0.04 kcal/min) with variable individual responses. When normalizing for body mass, this effect was lost (5.2%, p = 0.058). Omega-3s did not affect whole-body fat oxidation, and olive oil did not alter any parameter assessed. Omega-3 supplementation did not affect whole muscle, sarcolemmal, or mitochondrial FAT/CD36, FABPpm, FATP1 or FATP4 contents or mitochondrial electron chain and PDH proteins, but did increase the long form of UCP3 by 11%. In conclusion, supplementation with a high dose of omega-3s for 12 weeks increased RMR in a small and variable manner in a group of healthy young men. Omega-3 supplementation also had no effect on several proteins involved in skeletal muscle fat metabolism and did not cause mitochondrial biogenesis.
View
Effects of pomegranate extract on blood flow and running time to exhaustion
Article
Full-text available
  • May 2014
Recent research has shown that dietary nitrate has favorable effects on blood flow and exercise performance. The purpose of this randomized, double-blind, placebo-controlled crossover study was to investigate the acute effects of pomegranate extract on blood flow, vessel diameter, and exercise performance in active individuals. Nineteen men and women (mean ± SD: age, 22.2 ± 2.2 years; height, 174.8 ± 10.7 cm; body mass, 71.9 ± 13.5 kg) were randomly assigned to a placebo (PL) or pomegranate extract (PE) group. Participants performed a maximal oxygen consumption treadmill test to determine peak velocity (PV). Participants returned after 24–48 h and ingested either PL or PE. Brachial artery blood flow was assessed using ultrasound at baseline and 30 min post-ingestion (30minPI). Three treadmill runs to exhaustion were performed at 90%, 100%, and 110% PV. Blood flow was assessed immediately after each exercise bout and 30 min postexercise (30minPEx). After a 7–10 day washout, participants repeated the same procedures, ingesting the opposite supplement. Separate repeated measures ANOVAs were performed for blood flow, vessel diameter, and time to exhaustion (TTE). Blood flow was significantly augmented (p = 0.033) 30minPI with PE in comparison with PL. Vessel diameter was significantly larger (p = 0.036) 30minPEx with PE. Ingestion of PE was found to significantly augment TTE at 90% (p = 0.009) and 100% PV (p = 0.027). Acute ingestion of PE 30 min before exercise may enhance vessel diameter and blood flow and delay fatigue during exercise. Results of the current study indicate that PE is ergogenic for intermittent running, eliciting beneficial effects on blood flow.
View
Effect of carbohydrate or carbohydrate plus medium-chain triglyceride ingestion on cycling time trial performance
Article
  • Jan 2000
This study examined the effectiveness of ingesting a carbohydrate or carbohydrate + medium-chain triglycerides (MCT) on metabolism and cycling performance. Eight endurance-trained men [peak O 2 uptake = 4.71 ± 0.09 (SE) l/min] completed 35 kJ/kg as quickly as possible [time trial (TT)] while consuming 250 ml/15 min of either a 6% (wt/vol) carbohydrate solution (C), a 6% carbohydrate + 4.2% MCT solution (C+M), or a sweet placebo (P). Time to complete the set amount of work was reduced in both C and C+M compared with P by 7 and 5%, respectively (C: 166 ± 7 min; C+M: 169 ± 7 min; P: 178 ± 11 min; P < 0.01). Plasma glucose concentration was maintained at or above resting values throughout both C and C+M trials but decreased ( P < 0.05) below resting values in P at the completion of the TT. The estimated rate of carbohydrate oxidation was not different during the first 90 min of exercise but thereafter was reduced ( P < 0.05) in P and was maintained in both C and C+M. These data demonstrate that carbohydrate ingestion during exercise improves 100-km TT performance compared with a sweet placebo, but the addition of MCT does not provide any further performance enhancement.
View
Case Study: Nutrition and Training Periodization in Three Elite Marathon Runners
Article
  • Oct 2012
Laboratory-based studies demonstrate that fueling (carbohydrate; CHO) and fluid strategies can enhance training adaptations and race-day performance in endurance athletes. Thus, the aim of this case study was to characterize several periodized training and nutrition approaches leading to individualized race-day fluid and fueling plans for 3 elite male marathoners. The athletes kept detailed training logs on training volume, pace, and subjective ratings of perceived exertion (RPE) for each training session over 16 wk before race day. Training impulse/load calculations (TRIMP; min x RPE = load [arbitrary units; AU]) and 2 central nutritional techniques were implemented: periodic low-CHO-availability training and individualized CHO- and fluid-intake assessments. Athletes averaged ∼13 training sessions per week for a total average training volume of 182 km/wk and peak volume of 231 km/wk. Weekly TRIMP peaked at 4,437 AU (Wk 9), with a low of 1,887 AU (Wk 16) and an average of 3,082 ± 646 AU. Of the 606 total training sessions, ∼74%, 11%, and 15% were completed at an intensity in Zone 1 (very easy to somewhat hard), Zone 2 (at lactate threshold) and Zone 3 (very hard to maximal), respectively. There were 2.5 ± 2.3 low-CHO-availability training bouts per week. On race day athletes consumed 61 ± 15 g CHO in 604 ± 156 ml/hr (10.1% ± 0.3% CHO solution) in the following format: ∼15 g CHO in ∼150 ml every ∼15 min of racing. Their resultant marathon times were 2:11:23, 2:12:39 (both personal bests), and 2:16:17 (a marathon debut). Taken together, these periodized training and nutrition approaches were successfully applied to elite marathoners in training and competition.
View
Nutrition and athletic performance
Article
  • Jan 2000
It is the position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine that physical activity, athletic performance, and recovery from exercise are enhanced by optimal nutrition. These organizations recommend appropriate selection of food and fluids, timing of intake, and supplement choices for optimal health and exercise performance. This position paper reviews the current scientific data related to the energy needs of athletes, assessment of body composition, strategies for weight change, the nutrient and fluid needs of athletes, special nutrient needs during training, the use of supplements and nutritional ergogenic aids, and the nutrition recommendations for vegetarian athletes. During times of high physical activity, energy and macronutrient needs - especially carbohydrate and protein intake - must be met in order to maintain body weight, replenish glycogen stores, and provide adequate protein for building and repair of tissue. Fat intake should be adequate to provide the essential fatty acids and fat-soluble vitamins, as well as to help provide adequate energy for weight maintenance. Overall, diets should provide moderate amounts of energy from fat (20% to 25% of energy); however, there appears to be no health or performance benefit to consuming a diet containing less than 15% of energy from fat. Body weight and composition can affect exercise performance, but should not be used as the sole criterion for sports performance; daily weigh-ins are discouraged. Consuming adequate food and fluid before, during, and after exercise can help maintain blood glucose during exercise, maximize exercise performance, and improve recovery time. Athletes should be well-hydrated before beginning to exercise; athletes should also drink enough fluid during and after exercise to balance fluid losses. Consumption of sport drinks containing carbohydrates and electrolytes during exercise will provide fuel for the muscles, help maintain blood glucose and the thirst mechanism, and decrease the risk of dehydration or hyponatremia. Athletes will not need vitamin and mineral supplements if adequate energy to maintain body weight is consumed from a variety of foods. However, supplements may be required by athletes who restrict energy intake, use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high-carbohydrate diets with low micronutrient density. Nutritional ergogenic aids should be used with caution, and only after careful evaluation of the product for safety, efficacy, potency, and whether or not it is a banned or illegal substance. Nutrition advice, by a qualified nutrition expert, should only be provided after carefully reviewing the athlete's health, diet, supplement and drug use, and energy requirements.
View