Hitting the wall is when you deplete your stores of glycogen. We can store around 500-800g of carbohydrate stored as glycogen in the muscles and liver. 90-120 MINS

The body's largest stores of glycogen are found in the liver and skeletal muscles.  Individual glucosyl residues (ie, glucose monomers) in muscle and liver glycogen particles are linked by α(1→4) and α(1→6) glycosidic bonds and are released in the reactions of glycogenolysis.  Glycogen phosphorylase catalyzes the removal of most of the glucosyl residues, although debranching enzyme also releases the single glucose molecule that remains after it repositions three residues onto an adjacent linear chain.Binding of the hormone epinephrine to its receptor on the surface of muscle cells stimulates muscle glycogenolysis through activation of a signaling cascade (Figure 1).Figure 1  Stimulation of skeletal muscle glycogenolysis by epinephrine.The relative signal amplification (SA) at each step (I–IV in Figure 1) can be determined by comparing the number of active signaling molecules before (Mbefore) and after (Mafter) the step:SA=MafterMbeforeSA=𝑀after𝑀before Question 36The skeletal muscles collectively contain more than twice as much glucose stored in glycogen as is found in the liver.  Compared with the liver, the amount of glucose released into the blood from muscles is likely:A.greater from glycogenolysis, but less from gluconeogenesis.B.the same from glycogenolysis, but more from gluconeogenesis.C.less from both glycogenolysis and gluconeogenesis.D.the same from both glycogenolysis and gluconeogenesis.

Glycogen molecules are stored in liver and --------------

Many marathon runners “hit the wall” around mile 20. What does this tell you about glycogen?Group of answer choicesGlycogen stores are mostly depleted by mile 20.Oxidative phosphorylation of glycogen is too slow by mile 20.Exercise intensity is too high by mile 20 to be sustained by glycogen anymore.There is not enough oxygen by mile to continue using glycogen.

describe the structure of glycogen, and its importance as a carbohydrate reserve.

Well trained individuals may utilise less glycogen/carbohydrate for performance. But in reality the fitter we are and the faster we want to go, we continue to push the intensity, as a result glycogen depletion is still a very real thing even for the most highly trained individuals, hence peak performance determined by the ability to utilise carbs and fats effectively.