Ghosting said:
I used to think think this too. Until I saw this.
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Sports Med. 1991 Apr;11(4):232-43. Related Articles, Links
Regulation of glycogen resynthesis following exercise. Dietary considerations.
Friedman JE, Neufer PD, Dohm GL.
Department of Biochemistry, School of Medicine, East Carolina University, Greenville, North Carolina.
With the cessation of exercise, glycogen repletion begins to take place rapidly in skeletal muscle and can result in glycogen levels higher than those present before exercise. Understanding the rate-limiting steps that regulate glycogen synthesis will provide us with strategies to increase the resynthesis of glycogen during recovery from exercise, and thus improve performance. Given the importance of muscle glycogen to endurance performance, various factors which may optimise glycogen resynthesis rate and insure complete restoration have been of interest to both the scientist and athlete. The time required for complete muscle glycogen resynthesis after prolonged moderate intensity exercise is generally considered to be 24 hours provided approximately 500 to 700g of carbohydrate is ingested. Muscle glycogen synthesis rate is highest during the first 2 hours after exercise. Ingestion of 0.70g glucose/kg bodyweight every 2 hours appears to maximise glycogen resynthesis rate at approximately 5 to 6 mumol/g wet weight/h during the first 4 to 6 hours after exhaustive exercise. Further enhancement of glycogen resynthesis rate with ingestion of greater than 0.70g glucose/kg bodyweight appears to be limited by the constraints imposed by gastric emptying. Ingestion of glucose or sucrose results in similar muscle glycogen resynthesis rates while glycogen synthesis in liver is better served with the ingestion of fructose. Also, increases in muscle glycogen content during the first 4 to 6 hours after exercise are greater with ingestion of simple as compared with complex carbohydrate. Glycogen synthase activity is a key component in the regulation of glycogen resynthesis. Glycogen synthase enzyme exists in 2 states: the less active, more phosphorylated (D) form which is under allosteric control of glucose-6-phosphate, and the more active, less phosphorylated (I) form which is independent of glucose-6-phosphate. There is generally an inverse relationship between glycogen content in muscle and the percentage synthase in the activated (I) form. Exercise and insulin by themselves activate glycogen synthase by conversion to glycogen synthase I. Although small changes in the activity ratio (% I form) can lead to large changes in the rate of glycogen synthesis, glycogen synthase I appears to increase very little (approximately 25%) in response to glycogen depletion and returns to pre-exercise levels as glycogen levels return to normal. Thus glycogen resynthesis, which may increase 3- to 5-fold, may also be influenced by glucose-6-phosphate, which can activate glycogen synthase in the D form.(ABSTRACT TRUNCATED AT 400 WORDS)
Increasing muscle glycogen faster does not equalt faster protein synthesis rate.
Then you can read this:
Determinants of post-exercise glycogen synthesis during short-term recovery.
Jentjens R, Jeukendrup A.
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
The pattern of muscle glycogen synthesis following glycogen-depleting exercise occurs in two phases. Initially, there is a period of rapid synthesis of muscle glycogen that does not require the presence of insulin and lasts about 30-60 minutes. This rapid phase of muscle glycogen synthesis is characterised by an exercise-induced translocation of glucose transporter carrier protein-4 to the cell surface, leading to an increased permeability of the muscle membrane to glucose. Following this rapid phase of glycogen synthesis, muscle glycogen synthesis occurs at a much slower rate and this phase can last for several hours. Both muscle contraction and insulin have been shown to increase the activity of glycogen synthase, the rate-limiting enzyme in glycogen synthesis. Furthermore, it has been shown that muscle glycogen concentration is a potent regulator of glycogen synthase. Low muscle glycogen concentrations following exercise are associated with an increased rate of glucose transport and an increased capacity to convert glucose into glycogen.The highest muscle glycogen synthesis rates have been reported when large amounts of carbohydrate (1.0-1.85 g/kg/h) are consumed immediately post-exercise and at 15-60 minute intervals thereafter, for up to 5 hours post-exercise. When carbohydrate ingestion is delayed by several hours, this may lead to ~50% lower rates of muscle glycogen synthesis. The addition of certain amino acids and/or proteins to a carbohydrate supplement can increase muscle glycogen synthesis rates, most probably because of an enhanced insulin response.
However, when carbohydrate intake is high (>/=1.2 g/kg/h) and provided at regular intervals, a further increase in insulin concentrations by additional supplementation of protein and/or amino acids does not further increase the rate of muscle glycogen synthesis. Thus, when carbohydrate intake is insufficient (<1.2 g/kg/h), the addition of certain amino acids and/or proteins may be beneficial for muscle glycogen synthesis. Furthermore, ingestion of insulinotropic protein and/or amino acid mixtures might stimulate post-exercise net muscle protein anabolism. Suggestions have been made that carbohydrate availability is the main limiting factor for glycogen synthesis.
A large part of the ingested glucose that enters the bloodstream appears to be extracted by tissues other than the exercise muscle (i.e. liver, other muscle groups or fat tissue) and may therefore limit the amount of glucose available to maximise muscle glycogen synthesis rates. Furthermore, intestinal glucose absorption may also be a rate-limiting factor for muscle glycogen synthesis when large quantities (>1 g/min) of glucose are ingested following exercise.
THen when you get done reading that you will understand that the carbohydrate isn't the answer, amino's are and that glycogen synthesis rate are the same regardless.
Carbohydrate nutrition before, during, and after exercise.
Costill DL.
The role of dietary carbohydrates (CHO) in the resynthesis of muscle and liver glycogen after prolonged, exhaustive exercise has been clearly demonstrated. The mechanisms responsible for optimal glycogen storage are linked to the activation of glycogen synthetase by depletion of glycogen and the subsequent intake of CHO. Although diets rich in CHO may increase the muscle glycogen stores and enhance endurance exercise performance when consumed in the days before the activity, they also increase the rate of CHO oxidation and the use of muscle glycogen. When consumed in the last hour before exercise, the insulin stimulated-uptake of glucose from blood often results in hypoglycemia, greater dependence on muscle glycogen, and an earlier onset of exhaustion than when no CHO is fed. Ingesting CHO during exercise appears to be of minimal value to performance except in events lasting 2 h or longer.
The form of CHO (i.e., glucose, fructose, sucrose) ingested may produce different blood glucose and insulin responses, but the rate of muscle glycogen resynthesis is about the same regardless of the structure.
Then when you are done reading that you will understand that its NOT about muscle glycogen, its about the rate of protein sythesis and then you will read these.
Amino acids stimulate translation initiation and protein synthesis through an Akt-independent pathway in human skeletal muscle.
Liu Z, Jahn LA, Wei L, Long W, Barrett EJ.
Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
[email protected]
Studies in vitro as well as in vivo in rodents have suggested that amino acids (AA) not only serve as substrates for protein synthesis, but also as nutrient signals to enhance mRNA translation and protein synthesis in skeletal muscle. However, the physiological relevance of these findings to normal humans is uncertain. To examine whether AA regulate the protein synthetic apparatus in human skeletal muscle, we infused an AA mixture (10% Travesol) systemically into 10 young healthy male volunteers for 6 h. Forearm muscle protein synthesis and degradation (phenylalanine tracer method) and the phosphorylation of protein kinase B (or Akt), eukaryotic initiation factor 4E-binding protein 1, and ribosomal protein S6 kinase (p70(S6K)) in vastus lateralis muscle were measured before and after AA infusion. We also examined whether AA affect urinary nitrogen excretion and whole body protein turnover. Postabsorptively all subjects had negative forearm phenylalanine balances. AA infusion significantly improved the net phenylalanine balance at both 3 h (P < 0.002) and 6 h (P < 0.02). This improvement in phenylalanine balance was solely from increased protein synthesis (P = 0.02 at 3 h and P < 0.003 at 6 h), as protein degradation was not changed. AA also significantly decreased whole body phenylalanine flux (P < 0.004). AA did not activate Akt phosphorylation at Ser(473), but significantly increased the phosphorylation of both eukaryotic initiation factor 4E-binding protein 1 (P < 0.04) and p70(S6K) (P < 0.001).
We conclude that AA act directly as nutrient signals to stimulate protein synthesis through Akt-independent activation of the protein synthetic apparatus in human skeletal muscle.
Physiological hyperinsulinemia stimulates p70(S6k) phosphorylation in human skeletal muscle.
Hillier T, Long W, Jahn L, Wei L, Barrett EJ.
Department of Internal Medicine, Division of Endocrinology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA.
Using tracer methods, insulin stimulates muscle protein synthesis in vitro, an effect not seen in vivo with physiological insulin concentrations in adult animals or humans. To examine the action of physiological hyperinsulinemia on protein synthesis using a tracer-independent method in vivo and identify possible explanations for this discrepancy, we measured the phosphorylation of ribosomal protein S6 kinase (P70(S6k)) and eIF4E-binding protein (eIF4E-BP1), two key proteins that regulate messenger ribonucleic acid translation and protein synthesis. Postabsorptive healthy adults received either a 2-h insulin infusion (1 mU/min.kg; euglycemic insulin clamp; n = 6) or a 2-h saline infusion (n = 5). Vastus lateralis muscle was biopsied at baseline and at the end of the infusion period. Phosphorylation of P70(S6k) and eIF4E-BP1 was quantified on Western blots after SDS-PAGE. Physiological increments in plasma insulin (42 +/- 13 to 366 +/- 36 pmol/L; P: = 0.0002) significantly increased p70(S6k) (P: < 0.01), but did not affect eIF4E-BP1 phosphorylation in muscle. Plasma insulin declined slightly during saline infusion (P: = 0.04), and there was no change in the phosphorylation of either p70(S6k) or eIF4E-BP1. These findings indicate an important role of physiological hyperinsulinemia in the regulation of p70(S6k) in human muscle. This finding is consistent with a potential role for insulin in regulating the synthesis of that subset of proteins involved in ribosomal function.
The failure to enhance the phosphorylation of eIF4E-BP1 may in part explain the lack of a stimulatory effect of physiological hyperinsulinemia on bulk protein synthesis in skeletal muscle in vivo.
Little more research goes a long way
