Article

Independent and combined effects of liquid carbohydrate/essential amino acid ingestion on hormonal and muscular adaptations following resistance training in untrained men

School of Human Movement Studies, Charles Sturt University, Allen House 2.13, Bathurst, NSW, Australia.
Arbeitsphysiologie (Impact Factor: 2.3). 05/2006; 97(2):225-38. DOI: 10.1007/s00421-005-0127-z
Source: PubMed

ABSTRACT This investigation examined chronic alteration of the acute hormonal response associated with liquid carbohydrate (CHO) and/or essential amino acid (EAA) ingestion on hormonal and muscular adaptations following resistance training. Thirty-two untrained young men performed 12 weeks of resistance training twice a week, consuming ~675 ml of either, a 6% CHO solution, 6 g EAA mixture, combined CHO + EAA supplement or placebo (PLA). Blood samples were obtained pre- and post-exercise (week 0, 4, 8, and 12), for determination of glucose, insulin, and cortisol. 3-Methylhistidine excretion and muscle fibre cross-sectional area (fCSA) were determined pre- and post-training. Post-exercise cortisol increased (P<0.05) during each training phase for PLA. No change was displayed by EAA; CHO and CHO + EAA demonstrated post-exercise decreases (P<0.05). All groups displayed reduced pre-exercise cortisol at week 12 compared to week 0 (P<0.05). Post-exercise insulin concentrations showed no change for PLA; increases were observed for the treatment groups (P<0.05), which remained greater for CHO and CHO + EAA (P<0.001) than PLA. EAA and CHO ingestion attenuated 3-methylhistidine excretion 48 h following the exercise bout. CHO + EAA resulted in a 26% decrease (P<0.01), while PLA displayed a 52% increase (P<0.01). fCSA increased across groups for type I, IIa, and IIb fibres (P<0.05), with CHO + EAA displaying the greatest gains in fCSA relative to PLA (P<0.05). These data indicate that CHO + EAA ingestion enhances muscle anabolism following resistance training to a greater extent than either CHO or EAA consumed independently. The synergistic effect of CHO + EAA ingestion maximises the anabolic response presumably by attenuating the post-exercise rise in protein degradation.

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    • "Over a longitudinal time frame when muscle protein synthesis is elevated from resistance exercise training and nutritional intake, the increase in lean body mass may be accompanied by a decrease in fat mass [1]. This was demonstrated in a recent study where essential amino acid-carbohydrate supplements were ingested in conjunction with 12 weeks of resistance training in young men [15]. In this study, those who consumed the essential amino acid-carbohydrate after resistance exercise showed greater increases in fat free mass and larger declines in fat mass compared to other subjects that consumed essential amino acids only, carbohydrate only, or a placebo after resistance exercise. "
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    ABSTRACT: Increasing the rate of muscle protein synthesis is an energy consuming process that explains the acute elevations in resting energy expenditure (REE) observed 12 to 72 hours after a resistance exercise session. We hypothesized that multiple sessions of resistance exercise combined with the intake of amino acids would increase REE and alter the nonprotein respiratory exchange ratio (RER). Ten male participants completed two separate seven-day trials where REE and RER were measured on each morning via indirect calorimetry. On four consecutive days within each seven-day trial, acute resistance exercise was performed, and nutritional intake was manipulated by providing (1) amino acids and carbohydrate (AA-RT) or (2) nonnitrogenous, isoenergetic carbohydrate (CHO-RT) before and during each resistance exercise session. Average REE within the training period was 3.61% greater in AA-RT (7897 ± 252 kJ) compared to CHO-RT (7622 ± 289 kJ; ). RER declined () from baseline after each resistance exercise was initiated in both AA-RT (0.82 ± 0.01 to 0.77 ± 0.01) and CHO-RT (0.82 ± 0.02 to 0.77 ± 0.02). We conclude the provision of amino acids with multiple bouts of resistance exercise enhances energy expenditure at rest without altering the utilization of lipid.
    05/2013; 2013. DOI:10.5402/2013/948695
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    • "Studies examining the effect of protein supplementation on strength enhancement are limited and results have been inconclusive. Although some investigators have shown augmented strength gains from protein supplementation (Bird et al., 2006), others have reported no effects (Chromiak et al., 2004; Rankin et al., 2004). However , these studies have generally used untrained or recreationally trained individuals. "
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    ABSTRACT: I was encouraged to read Dr. Longo and colleagues' Letter to the Editor entitled "The best athletes in ancient Rome were vegetarian!"(Longo et al., 2008). These writers ask that we rethink the issue of what is an optimal dietary protein content for athletes by considering the diets that sustained the ancient gladiators of Rome. Historical evidence shows that humans of ancient times performed at intense levels while consuming 78% of their diets' as plant protein (Kanz and Grosschmidt, 2007). This anthropological fact, and some recent laboratory evidence, argues against the need to increase the protein RDA for athletes from 0.8 g of protein per kilogram of body weight per day to 1.2 to 1.4 g per kilogram per day (ACSM, 2000). Our research group found that amino acids make a small contribution (2 - 3% of total) to endurance energy needs (Lamont et al, 1999) and that athlete's have similar oxidation rates if corrections are made for oxygen consumption and fat-free body mass. Others report that a short-term training program of 38-days reduces amino acid use during exercise and down-regulates a critical enzyme in the oxidative pathway in order to spare this nutrient (McKenzie et al., 2000) Yet sport nutritionists and physiologists continue to recommend an increased protein RDA for this group. If one does a Google search using the words exercise and protein you would literally get millions of citations recommending the athlete to increase their protein intake. One reason for this continued recommendation, I believe, is that the laboratory procedure used to justify an increased protein RDA (field-based nitrogen balance measurements) has many methodological shortcomings that are not recognized by the sports science community (Lamont, 2008). The problems with this technique are so great that its scientific fidelity has been questioned (Lamont, 2008). And as Longo and colleagues have highlighted (2008) the Institute of Medicine concluded that the evidence for increasing the RDA in active individuals is not compelling (Washington, 2002). All of these facts speak to the argument that many have "jumped the gun" in recommending that athlete's increase their protein intake. The ancient (and modern) evidence indicates that we need to recalibrate our dietary protein recommendations for this group. This argument is compelling when we consider that protein and amino acid supplements are among the highest nutritional supplements consumed (Lawrence and Kirby, 2002)We appreciate Dr. Lamont's comments on the need to recalibrate dietary protein recommendations for athletes. Protein requirements for experienced athletes have been the subject of a long and ongoing scientific debate. For strength-trained individuals to maintain a positive nitrogen balance, it is suggested that they need to consume a protein intake of 1.6 to 1.8 g·kg-1·day-1 (American Dietetic Association et al., 2000). Half of American collegiate athletes use nutritional supplements, with protein supplementation being one of the most commonly used (Schenk and Costley, 2002).High protein intake in daily diet using protein supplementation is widely used to gain muscle mass and strength among athletes and coaches.It is commonly believed that high intensity training increases protein requirements. The concept that if more proteins are available to the exercising muscle, greater protein muscular synthesis occurs is diffuse in recreational and competitive athletes. This so widely accepted belief of protein supplementation and consequently high protein intake increases sport performances does not seem to be supported by scientific data.Sport magazines are full of articles in which the authors explains how to made the highest amount of protein and in the same pages we can find out protein supplementation sponsors and pictures of "hardcore" bodybuilders. We can therefore speculate about the origin of the huge diffusion of the "protein supplementation culture": it is possible that behind it there are just the economic interests of commercial producers, but other reasons are also possible.Protein supplementation indeed could be 'psychological doping' for athletes, so that this could be the fertile soil on which protein supplementation business may grow up.We should admit that the ability to achieve adequate protein intake for many collegiate athletes is compromised from inadequate nutrition attributed to low caloric intake, poor food choices, and irregular meals (Cole, 2005; Hinton, 2004), and this could be another reason why these athletes have to rely on protein supplementation to ingest their daily requirement of proteins.Studies examining the effect of protein supplementation on strength enhancement are limited and results have been inconclusive. Although some investigators have shown augmented strength gains from protein supplementation (Bird et al., 2006), others have reported no effects (Chromiak et al., 2004; Rankin et al., 2004). However, these studies have generally used untrained or recreationally trained individuals.A recent study (Hoffman, 2007) evaluates the effect of protein supplementation on athletic performance and hormonal changes in 21 experienced collegiate strength/power athletes participating in a 12-week resistance training program. Although protein supplementation appeared to augment lower body strength development, similar upper body strength, anaerobic power and lean tissue changes do not provide clear evidence in supporting the efficacy of a 12-week protein supplementation period in experienced resistance trained athletes.Kraemer et al., 1998 reported no differences in training volume or intensity in experienced resistance-trained men during several days of protein supplementation.In 2001, the American Heart Association published a statement on dietary protein and weight reduction and suggested that individuals following such a diet may be at potential risk for metabolic, cardiac, renal, bone and liver diseases (St. Jeor et al., 2001).Charles Darwin remarked: "The most extraordinary workers I ever saw, the labourers in the mines of Chile, live exclusively on vegetable food, including many seeds of leguminous plants." Vegetable proteins, when combined to provide for all of the essential amino acids, provide an excellent source for protein, considering that they will likely result in a reduction in the intake of saturated fat and cholesterol. Vegetable sources of protein also provide numerous other nutrients such as phytochemicals and fiber that are also highly regarded in the diet (Hoffman, 2004)Considering the paucity of studies examining protein supplementation in experienced athletes for long period of time, further studies are warranted to examine the optimal protein intake for the health of athletes, and to ameliorate sport performance.Finally, we can consider that, for the modern sportsman, the hunger for gaining "hardcore" muscles becomes as pointless as it would have been for a Roman legionnaire or for a gladiator
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    • "Several other studies have reported greater gains in strength and lean mass after 6- 10 wk of heavy resistance training when a post-exercise protein supplement was ingested compared to carbohydrate (Candow et al., 2006; Kerksick et al., 2006). Another study reported a synergistic effect of protein + carbohydrate such that the effect of ingesting both on muscle anabolism was greater that protein or carbohydrate alone (Bird et al., 2006), and Cribb et al. (2006) suggested that training-induced gains in lean mass were higher after whey compared to casein ingestion. In contrast to studies that have reported differential effect of nutrient ingestion, other have found no difference in strength or lean mass gains induced by protein versus carbohydrate ingestion after resistance training (Chromiak et al., 2004; Beck et al., 2007). "
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    ABSTRACT: World records for athletic events continue to improve and in the search for superior methods to gain a competitive edge, coaches and athletes are constantly searching for the latest "magic bullet". Although it is assumed that optimal adaptation to the demands of repeated training sessions requires a diet that can sustain muscle energy reserves, this premise does not consider the unsolved longstanding question of whether it is a lack or a surplus of a substrate that triggers the training adaptation. As such, recent scientific enquiry has re-focused attention on the role of substrate availability before, during, and after training to amplify the training adaptation. There has also been a resurgence of interest in the potential for protein ingestion to improve performance and/or promote training-induced adaptations in skeletal muscle. Altitude training (real or simulated) is now an accepted part of competition preparation for many athletic events, and such interventions attract their own nutritional issues. These and other diet-training interactions with the potential to alter training adaptation and performance are discussed.
    Journal of Sports Sciences 12/2007; 25 Suppl 1:S115-24. DOI:10.1080/02640410701607411 · 2.10 Impact Factor
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