Thread: PWO Thoughts
06-08-2005, 05:45 PM #1
I myself use Dextrose PWO. A 2:1 raion of simple Carbs to Protein, however I have found some compeling arguments that say glycogen synthesis in insulin independent in its first stage. And that quicker glycogen sythesis does not result in quicker protein synthesis. These arguments advocated the use of Low-GI carbs stating that it made no difference. I'd like to believe we are all doing it the right way over here including myself. Here's a few studies, can any one (perhaps alot smarter than I) see if these studies are bullshit or not!
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.
06-08-2005, 05:46 PM #2
Here's another one:
Regulation of GLUT4 protein and glycogen synthase during muscle glycogen synthesis after exercise.
Ivy JL, Kuo CH.
Department of Kinesiology, The University of Texas at Austin, 78712, USA.
The pattern of muscle glycogen synthesis following its depletion by exercise is biphasic. Initially, there is a rapid, insulin independent increase in the muscle glycogen stores. This is then followed by a slower insulin dependent rate of synthesis. Contributing to the rapid phase of glycogen synthesis is an increase in muscle cell membrane permeability to glucose, which serves to increase the intracellular concentration of glucose-6-phosphate (G6P) and activate glycogen synthase. Stimulation of glucose transport by muscle contraction as well as insulin is largely mediated by translocation of the glucose transporter isoform GLUT4 from intracellular sites to the plasma membrane. Thus, the increase in membrane permeability to glucose following exercise most likely reflects an increase in GLUT4 protein associated with the plasma membrane. This insulin-like effect on muscle glucose transport induced by muscle contraction, however, reverses rapidly after exercise is stopped. As this direct effect on transport is lost, it is replaced by a marked increase in the sensitivity of muscle glucose transport and glycogen synthesis to insulin. Thus, the second phase of glycogen synthesis appears to be related to an increased muscle insulin sensitivity. Although the cellular modifications responsible for the increase in insulin sensitivity are unknown, it apparently helps maintain an increased number of GLUT4 transporters associated with the plasma membrane once the contraction-stimulated effect on translocation has reversed. It is also possible that an increase in GLUT4 protein expression plays a role during the insulin dependent phase.
06-08-2005, 07:08 PM #3
i better not be wasting my time w/ pwo meals
06-09-2005, 05:57 AM #4
Obvisously you aren't wasting your time PWO. However these recent studies are saying that the type of CHO ingested PWO doesn't matter. So I guess the question becomes is Low-GI healthier in the long run? I've been doing some research for using Dex etc...The studies used by Berardi etc... are all much older studies and perhaps out of date, gotta look into it more. But interesting non the less.
06-09-2005, 06:28 AM #5
deff intresting ! ne up for an experiment
06-09-2005, 07:00 AM #6
06-09-2005, 07:04 AM #7
i did see a long thread bout this tho
Swole cat & Ern dog cant remember the name
06-09-2005, 08:35 AM #8
My main concern here is, how glycogen depleting is weight training. I mean I hit the gym for about a good 45 min to an hour. Does that deplete enough glycogen to where I need a 80g Dex shake followed by 80 more grams of complex carbs. It seems that these studies state teh importance of Amino Acids PWO and the type of CHO does not matter. Through in the fact that weight training turn the body into an insulin sensitive state it would abviously not take much to get the insulin spike that we are seeking. Protein can raise insulin levels alone. I'm gonna try and find a study that indicates increased glyocogen sythesis increases protein synthesis.
06-09-2005, 09:00 AM #9
Sorry, I never stated which article was sayi8ng the type of carb made a minimal differece:
Carbohydrate nutrition before, during, and after exercise.
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.
06-09-2005, 09:15 AM #10Originally Posted by JuicedINmd
Point being, you may not NEED them, but you do need the carbs for growth and new muscle developement.
06-09-2005, 09:25 AM #11
I totally agree with you thats the reasoning I have used when using Dex for Cutting or Bulking. I think we all will agree that the PWO timefram is the best time to get any type of carbs in. But since it is appearant in these studies that A. Insulin is not needed in the first phase B. A more rapid rate of glycogen synthesis does not result in a faster rate of protein synthesis. Why jack insulin sky high? When perhaps using a more wholesome CHO would be more beneficial down the road. This statement also has me a bit concerned:
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.
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