Asker Jeukendrup

Asker Jeukendrup
Loughborough University | Lough · School of Sport, Exercise and Health Sciences

PhD

About

322
Publications
435,477
Reads
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24,539
Citations
Introduction
Recognized as one of the world’s leading sports nutrition experts, Asker Jeukendrup now runs a consulting business mysportscience Ltd that communicates science and translates this into practical guidelines. He is still involved in research and publishing, and continues the strive for evidence based practice in sport.
Additional affiliations
January 2012 - present
Loughborough University
Position
  • Professor
June 2011 - present
GSSI
Position
  • Gatorade Sports Science Institute
January 2011 - March 2016
Loughborough University
Position
  • Global Senior Director GSSI and visiting Professor

Publications

Publications (322)
Article
Full-text available
Gastrointestinal problems are common, especially in endurance athletes, and often impair performance or subsequent recovery. Generally, studies suggest that 30-50 % of athletes experience such complaints. Most gastrointestinal symptoms during exercise are mild and of no risk to health, but hemorrhagic gastritis, hematochezia, and ischemic bowel can...
Article
Full-text available
There have been significant changes in the understanding of the role of carbohydrates during endurance exercise in recent years, which allows for more specific and more personalized advice with regard to carbohydrate ingestion during exercise. The new proposed guidelines take into account the duration (and intensity) of exercise and advice is not r...
Article
Full-text available
The objective of this article is to provide a review of the fundamental aspects of body fluid balance and the physiological consequences of water imbalances, as well as discuss considerations for the optimal composition of a fluid replacement beverage across a broad range of applications. Early pioneering research involving fluid replacement in per...
Article
Full-text available
Summary High-carbohydrate diets have been commonplace in the athletic population for many years but more recently high-fat diets have gained popularity. It is becoming more and more clear that in trained athletes extreme dietary and training regimes are not ne- cessary to achieve optimal muscle glycogen stores. With adequate carbohydrate intake (7-...
Article
Professional cycle racing is one of the most demanding of all sports combining extremes of exercise duration, intensity and frequency. Riders are required to perform on a variety of surfaces (track, road, cross-country, mountain), terrains (level, uphill and downhill) and race situations (criterions, sprints, time trials, mass-start road races) in...
Article
There has been substantial progress in the knowledge of exercise and type 1 diabetes, with the development of guidelines for optimal glucose management. In addition, an increasing number of people living with type 1 diabetes are pushing their physical limits to compete at the highest level of sport. However, the post-exercise recovery routine, part...
Article
Full-text available
Hypohydration increases physiological strain and reduces physical and technical soccer performance, but there are limited data on how fluid balance responses change between different types of sessions in professional players. This study investigated sweat and fluid/carbohydrate intake responses in elite male professional soccer players training at...
Article
Full-text available
PRESENT 2020: Texto que desarrolla la lista de verificación para el adecuado informe de la evidencia en ensayos clínicos de deporte y nutrición del ejercicio (Traducción Inglés-Español)
Article
Full-text available
Football is a global game which is constantly evolving, showing substantial increases in physical and technical demands. Nutrition plays a valuable integrated role in optimising performance of elite players during training and match-play, and maintaining their overall health throughout the season. An evidence-based approach to nutrition emphasising...
Article
Full-text available
PRESENT 2020: Texto que desarrolla la lista de verificación para el adecuado informe de la evidencia en ensayos clínicos de deporte y nutrición del ejercicio (Traducción Inglés-Español)
Article
Some readers may not have access to the full paper, so a properly formatted and well-written abstract is imperative. Authors should give priority to information about the current study rather than using the abstract for an extensive background or rationale. 2a Methods: Key information regarding the study design, methods, and population should be su...
Article
Purpose: Large inter-individual variation exists in maximal fat oxidation rates (MFO) and the exercise intensity at which it occurs (FATMAX). However, there is no data describing the shape of the fat oxidation curve or, if individual differences exist when tested on separate occasions. Furthermore, there is limited data on fat metabolism in profes...
Article
Distance events in Athletics include cross country, 10,000-m track race, half-marathon and marathon road races, and 20- and 50-km race walking events over different terrain and environmental conditions. Race times for elite performers span ∼26 min to >4 hr, with key factors for success being a high aerobic power, the ability to exercise at a large...
Article
From the breakthrough studies of dietary carbohydrate and exercise capacity in the 1960s through to the more recent studies of cellular signaling and the adaptive response to exercise in muscle, it has become apparent that manipulations of dietary fat and carbohydrate within training phases, or in the immediate preparation for competition, can prof...
Article
Full-text available
The gastrointestinal (GI) tract plays a critical role in delivering carbohydrate and fluid during prolonged exercise and can therefore be a major determinant of performance. The incidence of GI problems in athletes participating in endurance events is high, indicating that GI function is not always optimal in those conditions. A substantial body of...
Article
Full-text available
It is becoming increasingly clear that adaptations, initiated by exercise, can be amplified or reduced by nutrition. Various methods have been discussed to optimize training adaptations and some of these methods have been subject to extensive study. To date, most methods have focused on skeletal muscle, but it is important to note that training eff...
Article
Full-text available
Peak exogenous carbohydrate oxidation rates typically reach ~1 g·min⁻¹ during exercise when ample glucose or glucose polymers are ingested. Fructose co-ingestion has been shown to further increase exogenous carbohydrate oxidation rates. The purpose of this study was to assess the impact of fructose co-ingestion provided either as a monosaccharide o...
Article
Full-text available
Introduction: The aim of this study was to describe maximal fat oxidation (MFO) rates in an athletic population. Method: In total, 1121 athletes (933 males and 188 females), from a variety of sports and competitive level, undertook a graded exercise test on a treadmill in a fasted state (≥5 h fasted). Rates of fat oxidation were determined using...
Article
Full-text available
Purpose: To determine effects of intensified training (IT) and carbohydrate supplementation on overreaching and immunity. Methods: In a randomized, double-blind, crossover design, 13 male cyclists (age 25 ± 6 years, [Formula: see text] 72 ± 5 ml/kg/min) completed two 8-day periods of IT. On one occasion, participants ingested 2 % carbohydrate (L...
Article
Full-text available
Purpose: Monitoring mood state is a useful tool for avoiding non-functional overreaching (NFOR). Brain derived neurotrophic factor (BDNF) is implicated in stress-related mood disorders. The purpose of the present study was to investigate the impact of intensified training-induced mood disturbance on plasma BDNF concentrations at rest and in respon...
Article
Full-text available
Few studies have investigated the effects of exercise training on sleep physiology in well-trained athletes. We investigated changes in sleep markers, mood state and exercise performance in well-trained cyclists undergoing short-term intensified training and carbohydrate nutritional intervention. Thirteen highly-trained male cyclists (age: 25 ± 6y,...
Article
Full-text available
Intermittent sports (e.g., team sports) are diverse in their rules and regulations but similar in the pattern of play; that is, intermittent high-intensity movements and the execution of sport-specific skills over a prolonged period of time (~1-2 h). Performance during intermittent sports is dependent upon a combination of anaerobic and aerobic ene...
Data
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Article
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It is possible that dietary nitrate (NO3 (-)) supplementation may improve both physical and cognitive performance via its influence on blood flow and cellular energetics. To investigate the effects of dietary NO3 (-) supplementation on exercise performance and cognitive function during a prolonged intermittent sprint test (IST) protocol, which was...
Article
Performance in many sports is at least partially dependent on motor control, coordination, decision-making, and other cognitive tasks. This review summarizes available evidence about the ingestion of selected nutrients or isolated compounds (dietary constituents) and potential acute effects on motor skill and/or cognitive performance in athletes. D...
Conference Paper
Full-text available
The physical, mental and hormonal responses to short-term intensified training in well-trained cyclists with a high carbohydrate nutritional intervention
Conference Paper
RESULTS: Both WP+AFRTop and WP+RegTop resulted in a ~1.8 fold greater cumulative ΔHb relative to CON (p ≤ 0.05). When both clothing ensembles were compared, EHL and ΔHb were similar at the end of all four exercise and recovery periods (all p > 0.05). In parallel, the cumulative ΔHb for all exercise/recovery cycles was not different between WP+AFRTo...
Conference Paper
Upper respiratory tract infections are particularly prevalent during intensified training (IT) or competition, and in athletes suffering from overreaching (OR). High carbohydrate intake may play a role in prevention of OR and alleviate potential immunosuppression. PURPOSE: To determine the effects of IT and carbohydrate supplementation on plasma ho...
Article
Full-text available
We developed a digital dietary analysis tool for athletes (DATA) using a modified 24-h recall method and an integrated, customized nutrient database. The purpose of this study was to assess DATA's validity and relative validity by measuring its agreement with registered dietitians' (RDs) direct observations (OBSERVATION) and 24-h dietary recall int...
Article
Full-text available
It is often suggested that coffee causes dehydration and its consumption should be avoided or significantly reduced to maintain fluid balance. The aim of this study was to directly compare the effects of coffee consumption against water ingestion across a range of validated hydration assessment techniques. In a counterbalanced cross-over design, 50...
Article
The acute effects of green tea extract (GTE) on plasma metabolites in vivo are largely unknown. In this study, the transient changes in total and free concentrations of catechins were measured in plasma from healthy males following the consumption of a single GTE dose. Furthermore, the acute effects on endogenous metabolites were assessed two hours...
Article
The aim of this study was to investigate if duration of decaffeinated green tea extract (dGTE) ingestion plays a role in augmenting fat oxidation rates during moderate-intensity exercise. In a cross-over, placebo controlled design, 19 healthy males [x± SD age: 21 ± 2 y; weight 75.0 ± 7.0 kg; body mass index (BMI) 23.2 ± 2.2 kg[BULLET OPERATOR]m; ma...
Chapter
Originally, studies investigated the role of high muscle glycogen stores at the onset of exercise (carbo-loading) on exercise performance and recently, research has focused more on the potential role of carbohydrate ingested just before and during exercise. Studies have investigated the effects of different feeding regimens, different types of carb...
Article
Full-text available
The present study examined whether a high protein diet prevents the attenuated leukocyte redistribution in response to acute exercise caused by a large volume of high-intensity exercise training. Eight cyclists (VO2max: 64.2 ± 6.5 mL kg(-1)·min(-1)) undertook two separate weeks of high-intensity training while consuming either a high protein diet (...
Article
Durante los últimos años se han producido cambios significativos en la comprensión del papel que juegan los carbohidratos durante el ejercicio, y esto permite realizar un asesoramiento más específico y más individualizado en cuanto a la ingestión de carbohidratos durante el ejercicio. Las nuevas directrices propuestas tienen en cuenta la duración (...
Article
Full-text available
At rest, administration of the short-chain fatty acid acetate suppresses fat oxidation without affecting carbohydrate utilization. The combined effect of increased acetate availability and exercise on substrate utilization is, however, unclear. With local ethics approval, we studied the effect of ingesting either sodium acetate (NaAc) or sodium bic...
Article
Nutrition is an integral part of all athletes' lives; however, the importance of proper nutrition is even greater for the adolescent athlete. An athlete's nutrition provides both the fuel for energy and the foundation necessary to recover from exercise stress. Inadequate nutrition can result not only in diminished performance but also in delays in...
Article
Carbohydrates during exercise can improve exercise performance even when the exercise intensity is high (>75% V˙O2max) and the duration relatively short (approximately 1 h), but the underlying mechanisms for the ergogenic effects are different from those during more prolonged exercise. Studies have even shown effects of oral carbohydrate mouth rins...
Article
Full-text available
Dietary supplementation with beetroot juice (BR) containing ~5-8 mmol of inorganic nitrate (NO3(-)) increases plasma nitrite concentration ([NO2(-)]), reduces blood pressure, and may positively influence the physiological responses to exercise. However, the dose-response relationship between the volume of BR ingested and the physiological effects i...
Article
Full-text available
There is consistent evidence supporting the ergogenic effects of caffeine for endurance based exercise. However, whether caffeine ingested through coffee has the same effects is still subject to debate. The primary aim of the study was to investigate the performance enhancing effects of caffeine and coffee using a time trial performance test, while...
Article
Full-text available
Carbohydrate intake during prolonged exercise has been shown to increase endurance capacity and improve performance. Until recently, the advice was to ingest 30-60 g of carbohydrate per hour. The upper limit was based on studies that demonstrated that intakes greater than 60-70 g/h would not result in greater exogenous carbohydrate oxidation rates....
Article
Full-text available
Green tea is made from the leaves of the Camellia sinensis L plant, which is rich in polyphenol catechins and caffeine. There is increasing interest in the potential role of green tea extract (GTE) in fat metabolism and its influence on health and exercise performance. A number of studies have observed positive effects of GTE on fat metabolism at r...
Conference Paper
Full-text available
It is often suggested that coffee causes dehydration and should be avoided or reduced to maintain fluid balance. The aim of this study was to directly compare the chronic effects of moderate coffee consumption against water across a range of standardized hydration assessment techniques. In a counterbalanced crossover design, 50 habitual coffee-drin...
Article
Purpose: The aim of this study was to investigate the effects of 1 and 7 d of green tea extract (GTE) ingestion on whole body fat oxidation during moderate-intensity exercise. Methods: Thirty-one men completed two exercise trials (60-min cycle, 50% Wmax). After the baseline trial (day 0), subjects were randomly assigned to one of three condition...
Article
Background: Green tea catechins have been hypothesized to increase energy expenditure and fat oxidation by inhibiting catechol-O-methyltransferase (COMT) and thus promoting more sustained adrenergic stimulation. Metabolomics may help to clarify the mechanisms underlying their putative physiological effects. Objective: The study investigated the...
Article
Full-text available
We examined whether exercise-induced lymphocytosis and lymphocytopenia are impaired with high-intensity training. Eight trained cyclists (VO(2max) = 64.2 ± 6.5 mL · kg(-1) · min(-1)) undertook 1 wk of normal-intensity training and a second week of high-intensity training. On day 7 of each week, participants performed a cycling task, consisting of 1...
Article
Although sports performance is multifactorial, it is clear that muscle performance plays a major role in most sports. Fatigue is associated with metabolic processes in the muscle and by manipulating these processes, exercise can be maintained for longer or power output and speed can be enhanced. The key metabolic factors in sustaining and modulatin...
Article
Not surprisingly, we originally intended that the last word on our A-Z supplement series should come under ‘Z’. However, we did not anticipate the attention provided to a topic that we had overlooked under ‘P’, namely peptides. Some peptides—technically defined as chains of amino acids of lengths ranging from 2 to 50—can be considered nutrients. In...
Article
The term 'fat burner' is used to describe nutrition supplements that are claimed to acutely increase fat metabolism or energy expenditure, impair fat absorption, increase weight loss, increase fat oxidation during exercise, or somehow cause long-term adaptations that promote fat metabolism. Often, these supplements contain a number of ingredients,...
Article
Full-text available
Endurance sports are increasing in popularity and athletes at all levels are looking for ways to optimize their performance by training and nutrition. For endurance exercise lasting 30 min or more, the most likely contributors to fatigue are dehydration and carbohydrate depletion, whereas gastrointestinal problems, hyperthermia, and hyponatraemia c...
Article
There is little information about the actual nutrition and fluid intake habits and gastrointestinal (GI) symptoms of athletes during endurance events. This study aimed to quantify and characterize energy, nutrient, and fluid intakes during endurance competitions and investigate associations with GI symptoms. A total of 221 endurance athletes (male...
Article
Full-text available
To investigate the mechanisms underpinning modifications in glucose homeostasis and insulin sensitivity 24 h after a bout of resistance exercise (RE) with or without protein ingestion. Twenty-four healthy males were assigned to a control (CON; n = 8), exercise (EX; n = 8) or exercise plus protein condition (EX+PRO; n = 8). Muscle biopsy and blood s...
Article
Full-text available
An athlete's carbohydrate intake can be judged by whether total daily intake and the timing of consumption in relation to exercise maintain adequate carbohydrate substrate for the muscle and central nervous system ("high carbohydrate availability") or whether carbohydrate fuel sources are limiting for the daily exercise programme ("low carbohydrate...
Article
Full-text available
The way in which metabolic fuels are utilized can alter the expression of behaviour in the interests of regulating energy balance and fuel availability. This is consistent with the notion that the regulation of appetite is a psychobiological process, in which physiological mediators act as drivers of behaviour. The glycogenostatic theory suggests t...
Article
We investigated the effects of exercise training on adipose tissue and skeletal muscle GLUT4 expression in patients with type 2 diabetes (T2D). Muscle and adipose tissue samples were obtained before and after 4-weeks of exercise training in seven patients with T2D [47 ± 2 years, body mass index (BMI) 28 ± 2]. Seven control subjects (54 ± 4, BMI 30...
Article
The purpose of the present study was to examine the effect of increased protein intake on short-term decrements in endurance performance during a block of high-intensity training. Trained male cyclists (VO(2max) = 64.2 ± 6.5 mL·kg(-1)·min(-1)) completed two 3-wk trials both divided equally into normal (NOR), intensified (INT), and recovery (REC) tr...