there is plenty of solid research supporting dextrose/malto/etc. pwo
Q: What are the properties of glycogen? And why are these properties so vital post workout?
A: Glycogen is a polysaccharide, (C6H10O5)n that is the main form of carbohydrate storage in animals and humans and occurs primarily in the liver and muscle tissue. It is readily converted to glucose as needed by the body to satisfy its energy needs (21), such as during intense training.
To enhance the progress of muscular strength and size with heavy-resistance body building programs, optimal conditions for recovery from training sessions are imperative, primarily glycogen re-synthesis (22).
Recovery occupies the coordinated operation of multiple physiological processes that are heavily influenced by the accessibility and actions of exclusive hormones and nutrients (16, 17).
Both qualitative and quantitative modifications in skeletal muscle contractile proteins are all supported and signaled by a horde of systematic -trophic influences from hormones to nutrient availability (18, 19).
Markedly, concentric and eccentric contractions disrupt or damage certain muscle fibers that must undertake a remodeling restoration process. Dietary nutrients, hormones, and growth factors interact to regulate this remodeling of skeletal muscle proteins (5).
One primal factor associated with muscular fatigue is depletion of muscle glycogen (1).
These stores must be replaced rapidly during the post-workout initial recovery phase in order for performance to be reproducible in a subsequent exercise bout(s).
Glycogen synthesis may be restricted by blood glucose concentration, glucose transport, and the activity of the enzymes involved in the pathway, particularly glycogen synthase (10).
Body building training programs provide conditions within skeletal muscle to support the rapid synthesis of glycogen.
Glycogen synthase action is inversely relative to glycogen intensity (23); as a result of the glycogen-depleted state post-training, skeletal muscle (24) and hepatic glycogen synthase activity are raised (13).
Basal glucose transport within skeletal muscle occurs via GLUT-4 (A powerhouse effect of insulin is the stimulation of glucose transport via the translocation of the insulin responsive glucose transporter, GLUT4, to the plasma membrane) (14).
Nevertheless, the ability of skeletal muscle to take up glucose is relative, due to adjustments in the GLUT-4 content of the sarcolemal membrane.
Image 1. Atrophic muscle fibers. The sarcolemal membranes of these two atrophic fibers have a wavy appearance. Courtesy: Department of Pathology; Virginia Commonwealth University;
There are hypothesized to be one or more intracellular pools of GLUT-4 proteins, which are translocated to the sarcolema in response to both increased insulin concentration (20) and prior exercise (9); these effects are additive (6).
In the post-workout period, therefore, muscle membrane permeability to glucose is high, thus favoring the accretion of glycogen replacement. However, if rapid carbohydrate distribution is not provided during recovery, glycogen synthesis will be limited because the rate of endogenous glucose production from gluconeogenic precursors such as alanine and glycerol is inadequate to support maximal rates of glycogen synthesis (15).
The ingestion of high GI carbohydrates increases glycogen synthesis in two ways.
The first (12) is increased substrate availability through the increased blood glucose concentration, which results in an increased glucose uptake due to mass action.
Moreover, the resultant increase in systemic insulin concentration stimulates the translocation of GLUT-4 transporters from an intracellular pool to the sarcolemal membrane (7).
The hormone insulin is also a powerful activator of glycogen synthase and inhibitor of glycogen phosphorylase (2).
The effectiveness of a specific carbohydrate in encouraging resynthesis of the carbohydrate stores is reliant on the insulin and glucose response to the carbohydrate load (4).
This is directly linked to gastric emptying and intestinal absorption rates. It is also associated with the insulinogenic potential of the carbohydrate, as indicated by the glycemic index (GI) of a carbohydrate.
The development of glycogen synthesis relies upon the accessibility of glycogenic substrate (
and the activity of the enzymes implicated in glycogen synthesis. These include hexokinase and glycogen synthase.
Prior exercise enhances skeletal muscle glucose transport (3) because of the translocation of GLUT-4 transporters from an intracellular pool to the sarcolemal membrane.
The inclination for skeletal muscle to extort blood glucose will thus be increased, and the glucose will tend to be directed toward glycogen synthesis because glycogen synthase is activated during recovery due to the low intramuscular glycogen concentration (23).
These conditions favoring the resynthesis of glycogen can be exploited (
by the provision of a quality carbohydrate source.
The consequential amplification in glucose availability and the insulin response to the glucose load would tend to stimulate (7) a further increase in the GLUT-4 content of the sarcolemal membrane.
Research has demonstrated (11) that there is a direct correlation between the rate of glycogen storage during recovery and total muscle GLUT-4 protein content.
On a side note, observational and empirical evidence makes it plainly obvious that the endocrinal state of the body builder post-workout is nothing like that of a sedentary individual.
A red herring argument is an attempt to offer evidence to support one proposition by arguing for a different one entirely, or dodging the main argument by going off on a tangent.
Oftentimes opponents of high GI carbohydrate supplementation post-workout will point to the dangers of excess insulin-spiking and glucose intake; however, this is a red herring argument. This claim is like comparing apples to oranges.
