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asker jeukendrup

Asker E Jeukendrup
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 effects also include adaptations in other tissues (e.g., brain, vasculature), improvements in the absorptive capacity of the intestine, increases in tolerance to dehydration, and other effects that have received less attention in the literature...
March 2017: Sports Medicine
Asker E Jeukendrup
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 evidence suggests that the GI system is highly adaptable. Gastric emptying as well as stomach comfort can be "trained" and perceptions of fullness decreased; some studies have suggested that nutrient-specific increases in gastric emptying may occur...
March 2017: Sports Medicine
Jorn Trommelen, Cas J Fuchs, Milou Beelen, Kaatje Lenaerts, Asker E Jeukendrup, Naomi M Cermak, Luc J C van Loon
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 or as part of the disaccharide sucrose on exogenous carbohydrate oxidation rates during prolonged exercise in trained cyclists. Ten trained male cyclists (VO2peak: 65 ± 2 mL∙kg-1∙min-1) cycled on four different occasions for 180 min at 50% Wmax during which they consumed a carbohydrate solution providing 1...
February 20, 2017: Nutrients
Rebecca K Randell, Ian Rollo, Timothy J Roberts, Kortney J Dalrymple, Asker E Jeukendrup, James M Carter
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 indirect calorimetry. RESULTS: The average MFO was 0.59 ± 0.18 g·min, ranging from 0.17 to 1...
January 2017: Medicine and Science in Sports and Exercise
Ida S Svendsen, Sophie C Killer, James M Carter, Rebecca K Randell, Asker E Jeukendrup, Michael Gleeson
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, VO2max 72 ± 5 ml/kg/min) completed two 8-day periods of IT. On one occasion, participants ingested 2 % carbohydrate (L-CHO) beverages before, during and after training sessions. On the second occasion, 6 % carbohydrate (H-CHO) solutions were ingested before, during and after training, with the addition of 20 g of protein in the post-exercise beverage...
May 2016: European Journal of Applied Physiology
Maria Francesca Piacentini, Oliver C Witard, Cajsa Tonoli, Sarah R Jackman, James E Turner, Arie K Kies, Asker E Jeukendrup, Kevin D Tipton, Romain Meeusen
CONTEXT: Monitoring mood state is a useful tool for avoiding nonfunctional overreaching. Brain-derived neurotrophic factor (BDNF) is implicated in stress-related mood disorders. PURPOSE: To investigate the impact of intensified training-induced mood disturbance on plasma BDNF concentrations at rest and in response to exercise. METHODS: Eight cyclists performed 1 wk of normal (NT), 1 wk of intensified (INT), and 1 wk of recovery (REC) training...
September 2016: International Journal of Sports Physiology and Performance
Lindsay B Baker, Ian Rollo, Kimberly W Stein, Asker E Jeukendrup
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 energy systems, both of which rely on muscle glycogen and/or blood glucose as an important substrate for energy production. The aims of this paper are to review: (1) potential biological mechanisms by which carbohydrate may impact intermittent sport performance; (2) the acute effects of carbohydrate ingestion on intermittent sport performance, including intermittent high-intensity exercise capacity, sprinting, jumping, skill, change of direction speed, and cognition; and (3) what recommendations can be derived for carbohydrate intake before/during exercise in intermittent sports based on the available evidence...
July 14, 2015: Nutrients
Christopher Thompson, Lee J Wylie, Jonathan Fulford, James Kelly, Matthew I Black, Sinead T J McDonagh, Asker E Jeukendrup, Anni Vanhatalo, Andrew M Jones
UNLABELLED: It is possible that dietary nitrate (NO3 (-)) supplementation may improve both physical and cognitive performance via its influence on blood flow and cellular energetics. PURPOSE: To investigate the effects of dietary NO3 (-) supplementation on exercise performance and cognitive function during a prolonged intermittent sprint test (IST) protocol, which was designed to reflect typical work patterns during team sports. METHODS: In a double-blind randomised crossover study, 16 male team-sport players received NO3 (-)-rich (BR; 140 mL day(-1); 12...
September 2015: European Journal of Applied Physiology
Lindsay B Baker, Ryan P Nuccio, Asker E Jeukendrup
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. Dietary constituents discussed include branched-chain amino acids, caffeine, carbohydrate, cocoa flavanols, Gingko biloba, ginseng, guarana, Rhodiola rosea, sage, L-theanine, theobromine, and tyrosine...
December 2014: Nutrition Reviews
Doris M Jacobs, Adrian B Hodgson, Rebecca K Randell, Krishna Mahabir-Jagessar-T, Ursula Garczarek, Asker E Jeukendrup, David J Mela, Silvina Lotito
We previously reported that a 7 day ingestion of caffeinated green tea extract (cGTE) induced marked metabolic differences during rest and exercise. Here, we report the metabolic effects of 1, 7, and 28 day ingestions of decaffeinated GTE (dGTE). In this crossover placebo-controlled study, 19 healthy males ingested dGTE or placebo (PLA) for 28 days, separated by a 28 day wash-out period. On days 1, 7, and 28, participants completed a 30 min cycling exercise 2 h after the ingestion of dGTE or PLA. Blood samples were collected at rest (t = 0 and 120 min) and during exercise (t = 150 min)...
October 8, 2014: Journal of Agricultural and Food Chemistry
Erick Prado de Oliveira, Roberto Carlos Burini, Asker Jeukendrup
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 present serious medical challenges. Three main causes of gastrointestinal symptoms have been identified, and these are either physiological, mechanical, or nutritional in nature...
May 2014: Sports Medicine
Asker Jeukendrup
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 restricted to the amount of carbohydrate; it also gives direction with respect to the type of carbohydrate. Studies have shown that during exercise lasting approximately 1 h in duration, a mouth rinse or small amounts of carbohydrate can result in a performance benefit...
May 2014: Sports Medicine
Lindsay B Baker, Lisa E Heaton, Kimberly W Stein, Ryan P Nuccio, Asker E Jeukendrup
BACKGROUND: 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 interviews using the USDA 5-step multiple-pass method (INTERVIEW), respectively. METHODS: Fifty-six athletes (14-20 y) completed DATA and INTERVIEW in randomized counter-balanced order...
2014: Nutrition Journal
Lindsay B Baker, Asker E Jeukendrup
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 persons suffering from diarrheal disease and in military, occupational, and athlete populations incurring exercise- and/or heat-induced sweat losses has provided much of the insight regarding basic principles on beverage palatability, voluntary fluid intake, fluid absorption, and fluid retention...
April 2014: Comprehensive Physiology
Sophie C Killer, Andrew K Blannin, Asker E Jeukendrup
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 male coffee drinkers (habitually consuming 3-6 cups per day) participated in two trials, each lasting three consecutive days. In addition to controlled physical activity, food and fluid intake, participants consumed either 4×200 mL of coffee containing 4 mg/kg caffeine (C) or water (W)...
2014: PloS One
Adrian B Hodgson, Rebecca K Randell, Krishna Mahabir-Jagessar-T, Silvina Lotito, Theo Mulder, David J Mela, Asker E Jeukendrup, Doris M Jacobs
The acute effects of green tea extract (GTE) on plasma metabolites in vivo are largely unknown. In this parallel, double-blind 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 (559.2 mg total catechins, 120.4 mg caffeine). Furthermore, the acute effects on endogenous metabolites were assessed 2 h after GTE intake using four-phase metabolite profiling. The ratios of the catechin concentrations in plasma to those in the GTE followed the order ECG/CG > EC > GCG > EGCG > EGC > C > GC...
February 5, 2014: Journal of Agricultural and Food Chemistry
Rebecca K Randell, Adrian B Hodgson, Silvina B Lotito, Doris M Jacobs, Matthew Rowson, David J Mela, Asker E Jeukendrup
PURPOSE: The aim of this study was to investigate if the duration of decaffeinated green tea extract (dGTE) ingestion plays a role in augmenting fat oxidation rates during moderate-intensity exercise. METHODS: In a crossover, placebo-controlled design, 19 healthy males (mean ± SD; age = 21 ± 2 yr, weight = 75.0 ± 7.0 kg, body mass index = 23.2 ± 2.2 kg·m, maximal oxygen consumption [V˙O2max] = 55.4 ± 4.6 mL·kg·min) ingested dGTE and placebo (PLA) for 28 d, separated by a 28-d washout period...
June 2014: Medicine and Science in Sports and Exercise
Oliver C Witard, James E Turner, Sarah R Jackman, Arie K Kies, Asker E Jeukendrup, Jos A Bosch, Kevin D Tipton
The present study examined whether a high protein diet prevents the impaired leukocyte redistribution in response to acute exercise caused by a large volume of high-intensity exercise training. Eight cyclists (VO2max: 64.2±6.5mLkg(-1)min(-1)) undertook two separate weeks of high-intensity training while consuming either a high protein diet (3gkg(-1)proteinBM(-1)day(-1)) or an energy and carbohydrate-matched control diet (1.5gkg(-1)proteinBM(-1)day(-1)). High-intensity training weeks were preceded by a week of normal-intensity training under the control diet...
July 2014: Brain, Behavior, and Immunity
Asker E Jeukendrup
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 rinses compared to placebo with improvements typically between 2% and 3% during exercise lasting approximately 1 h. The effects appear more profound after an overnight fast, but effects are still present even after ingestion of a meal...
July 2013: Current Sports Medicine Reports
Asker Jeukendrup
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. The lower limit was an estimated guess of the minimum amount of carbohydrate required for ergogenic effects. In addition, the advice was independent of the type, the duration or the intensity of the activity as well as the level of athlete...
2013: Nestlé Nutrition Institute Workshop Series
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