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Sara Dean, Andrea Braakhuis and Carl Paton

Researchers have long been investigating strategies that can increase athletes’ ability to oxidize fatty acids and spare carbohydrate, thus potentially improving endurance capacity. Green-tea extract (epigallocatechin-3-gallate; EGCG) has been shown to improve endurance capacity in mice. If a green-tea extract can stimulate fat oxidation and as a result spare glycogen stores, then athletes may benefit through improved endurance performance. Eight male cyclists completed a study incorporating a 3-way crossover, randomized, placebo-controlled, double-blinded, diet-controlled research design. All participants received 3 different treatments (placebo 270 mg, EGCG 270 mg, and placebo 270 mg + caffeine 3 mg/kg) over a 6-day period and 1 hr before exercise testing. Each participant completed 3 exercise trials consisting of 60 min of cycling at 60% maximum oxygen uptake (VO2max) immediately followed by a self-paced 40-km cycling time trial. The study found little benefit in consuming green-tea extract on fat oxidation or cycling performance, unlike caffeine, which did benefit cycling performance. The physiological responses observed during submaximal cycling after caffeine ingestion were similar to those reported previously, including an increase in heart rate (EGCG 147 ± 17, caffeine 146 ± 19, and placebo 144 ± 15 beats/min), glucose at the 40-min exercise time point (placebo 5.0 ± 0.8, EGCG 5.4 ± 1.0, and caffeine 5.8 ± 1.0 mmol/L), and resting plasma free fatty acids and no change in the amount of carbohydrate and fat being oxidized. Therefore, it was concluded that green-tea extract offers no additional benefit to cyclists over and above those achieved by using caffeine.

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Jens Bangsbo, Fedon Marcello Iaia and Peter Krustrup

The physical demands in soccer have been studied intensively, and the aim of the present review is to provide an overview of metabolic changes during a game and their relation to the development of fatigue. Heart-rate and body-temperature measurements suggest that for elite soccer players the average oxygen uptake during a match is around 70% of maximum oxygen uptake (VO2 max). A top-class player has 150 to 250 brief intense actions during a game, indicating that the rates of creatine-phosphate (CP) utilization and glycolysis are frequently high during a game, which is supported by findings of reduced muscle CP levels and several-fold increases in blood and muscle lactate concentrations. Likewise, muscle pH is lowered and muscle inosine monophosphate (IMP) elevated during a soccer game. Fatigue appears to occur temporarily during a game, but it is not likely to be caused by elevated muscle lactate, lowered muscle pH, or change in muscle-energy status. It is unclear what causes the transient reduced ability of players to perform maximally. Muscle glycogen is reduced by 40% to 90% during a game and is probably the most important substrate for energy production, and fatigue toward the end of a game might be related to depletion of glycogen in some muscle fibers. Blood glucose and catecholamines are elevated and insulin lowered during a game. The blood free-fatty-acid levels increase progressively during a game, probably reflecting an increasing fat oxidation compensating for the lowering of muscle glycogen. Thus, elite soccer players have high aerobic requirements throughout a game and extensive anaerobic demands during periods of a match leading to major metabolic changes, which might contribute to the observed development of fatigue during and toward the end of a game.

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.1123/ijsn.6.4.323 Effects of Active Warm-Down and Carbohydrate Feeding on Free Fatty Acid Concentrations after Prolonged Submaximal Exercise Mahmoud S. El-Sayed * Angelheart J.M. Rattu * Xia Lin * Thomas Reilly * 12 1996 6 6 4 4 337 337 347 347 10.1123/ijsn.6.4.337 The Effect of Carbohydrate

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Athletes Andrea J. Braakhuis * Will G. Hopkins * Timothy E. Lowe * Elaine C. Rush * 4 2011 21 21 2 2 105 105 112 112 10.1123/ijsnem.21.2.105 Regular Dark Chocolate Consumption’s Reduction of Oxidative Stress and Increase of Free-Fatty-Acid Mobilization in Response to Prolonged Cycling Judith

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Fatty Acids Ine Wigernæs * Sigmund B. Strømme * Arne T. Høstmark * 12 2000 10 10 4 4 404 404 414 414 10.1123/ijsnem.10.4.404 Effects of Meal Form and Composition on Plasma Testosterone, Cortisol, and Insulin Following Resistance Exercise Richard J. Bloomer * Gary A. Sforzo * Betsy A. Keller

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Ulrika Andersson-Hall, Stefan Pettersson, Fredrik Edin, Anders Pedersen, Daniel Malmodin and Klavs Madsen

carbohydrates, mobilization of triglycerides and delivery of free fatty acids (FFA) via the blood stream ( Kiens et al., 2011 ; Spriet, 2011 ; van Loon et al., 2001 ). These metabolites are heavily influenced by activity level and diet. Various hormones, including glucagon, cortisol, growth hormone

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Samuel G. Impey, Kelly M. Hammond, Robert Naughton, Carl Langan-Evans, Sam O. Shepherd, Adam P. Sharples, Jessica Cegielski, Kenneth Smith, Stewart Jeromson, David L. Hamilton, Graeme L. Close and James P. Morton

assessments of insulin concentration were limited to pre- and postexercise time points per se. We also acknowledge the limitations associated with making inferences on muscle free fatty acid uptake on snapshot assessments of circulating NEFA per se. Nonetheless, given recent data demonstrating that acute

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Sang-Ho Lee, Steven D. Scott, Elizabeth J. Pekas, Jeong-Gi Lee and Song-Young Park

However, it seems more likely that octacosanol stimulates the conversion of lipids into energy, as an animal study reported that octacosanol intake resulted in greater serum free fatty acid levels, greater free fatty acid oxidation, and a decreased serum TG concentration when compared with a CON group. 9

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Trent Stellingwerff, James P. Morton and Louise M. Burke

technologies to investigate cellular signaling events over the past decade has expanded insights into the role of nutritional support in promoting adaptations to exercise. It is now known that many substrates, and in particular muscle glycogen and plasma free fatty acids, act not only as fuels for the exercise

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Manuel D. Quinones and Peter W.R. Lemon

maltodextrin (peak 2.5 vs. peak 20.3 mIU·ml −1 ) resulting in a more uniform serum glucose response as well as an increase in both serum free fatty acid and glycerol concentrations ( Roberts et al., 2011 ). Also, the RER with HMS appeared to be lower ( p  = .07) at both 60 min (0.92 vs. 0.95) and 90 min (0