To Dextrose or not to Dextrose

Young Gun

Whats everyone's views on Dextrose or maltodextrin PWO or even potentially pre WO.

I'm in the no or possibly when bulking camp. My PWO shake is usually 50 g whey 4 - 6 egg whites 1 tablespoon honey and 50g oats + 30g grits Ronnie C style (get them from the US)

Nick500

grits ! aren't they just a trade name for oatmeal?

Personally i do 1 scoop dextrose and 2 scoops whey, 6 egg whites 1 yolk, in water PWO. But i know a lot of people especially over at anabolicminds.com who swear by oats only, and our very own redspy (who left a couple months ago) used to swear by oats too.

The reason that i use dextrose is that it makes me recover much faster from my heavy workouts (i usually feel like a wreck after a heavy workout and am shaky), the dextrose sorts me out and i feel good.

From a muscle building perspective, I also take it because the greats like dorian used to do it. I'm definitely more about 'doing' than just research, if it worked for dorian then it can work for me, regardless of whether its tightly proved scientifically.

What do you guys think?

zx9rjas.

I used to use oats all the time when I started but then switched to maltodextrin for pre and post workout carb sources, but nowadays I've gone back to oats with fruit mixed in. Raisins, dates, apples and banana go really well.

J

Young Gun

Well thats what I thought until I bought some from Selfridges a few weeks ago. There not like oats taste very different. Plus the nutritional values are different.

Fair enough on the dextrose thing but not for me.

razg

The logic for Dextrose PWO is the following:

Muscle glycogen stores are replenished at a maximum rate by consuming maximally high GI carbs, and thus protein synthesis occurs at an optimal rate; additionally, an insulin spike will serve to inhibit cortisol and hence muscle catabolism while also promoting maximum nutrient uptake.

The logic against Dextrose PWO is the following:

Resistance training (i.e. weight training) is a low volume, high intensity activity and consequently does not significantly deplete muscle glycogen. Hence, the protein consumed PWO is of primary importance, and low GI carbs can be use to replace what little glycogen has been expended while minimizing the insulin spike and thus the fat additive affect of high GI carbs such as Dextrose.

Personally, I go with oats and whey nowadays. I occasionally thrown in around 10g of dextrose on the offchance that i've done some cardio to cause a glycogen depletive effect.

Young Gun

agreed ^^

finephysique

Vitargo is a much better carb source pre or post workout, the rest of the time I eat oats

Young Gun

On the topic for a pretty conclusive answer here goes.

Because glyocgen depletion and catabolism is highly overated post exercise. The hormonal respons to exercise in itself in anti-catabolic in nature. This is also the time when nutrient signaling is at its highest so the need for such a drastic insulin spike is not necessary. There has been no study confirming that the faster you restore glyogen stores the faster protein synthesis occurs. In fact protein synthesis is at its highest 24 hours after exercise. If proper nutrition is followed the need for a large amount of fast acting glucose is not warranted. There is also the the fact the glyocgen synthesis is biphasic and the frist stage (30 minutes post exercise) is insulin indpendent. This stage is more reliable on available amino acids as a substate rather than glucose. Exercise in itself increases glut4 permeability so the increased amounts of insulin are not needed to achieve this to improve trnasport. This is just some of the reasons I recommend a slower more stable release of insulin that will coincided wiht the second phase of glycogen resynthesis. Thjere is also the the reaosn of increased glucose storage due to a high insulin spike. Studies show that not all glucsoe in absorbed by the exercised muscle and there is increase chances of this being utilized by other tissues, adipose tissue being one of them

The pattern of muscle glycogen synthesis PWO is bi-phasic. The initial fast phase lasts around 30 minutes and happens WITHOUT THE PRESENCE OF INSULIN. So essentially by ingesting a FAST source of CHO, you're creating a situation that happens even without the intake.

Why do you need to create a situation that happens no matter what?

The bottom line is that fast levels of glycogen reloading doesn't result in faster protein synthesis.
Thus if both sources of carbs work then why ingest high GI it's obviously more likely to be stored as adipose tissue.

Young Gun

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 (> or =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.

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. zl3e@virginia.edu

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.

(pasted from bobo from AM)

Young Gun

Sorry for the length of posts just wished to conclude the issue.