Editing Exercise physiology (section)

=== Plasma glucose ===
Plasma glucose is said to be maintained when there is an equal rate of glucose appearance (entry into the blood) and glucose disposal (removal from the blood). In the healthy individual, the rates of appearance and disposal are essentially equal during exercise of moderate intensity and duration; however, prolonged exercise or sufficiently intense exercise can result in an imbalance leaning towards a higher rate of disposal than appearance, at which point glucose levels fall producing the onset of fatigue. Rate of glucose appearance is dictated by the amount of glucose being absorbed at the gut as well as liver (hepatic) glucose output. Although glucose absorption from the gut is not typically a source of glucose appearance during exercise, the liver is capable of catabolizing stored [[glycogen]] ([[glycogenolysis]]) as well as synthesizing new glucose from specific reduced carbon molecules (glycerol, pyruvate, and lactate) in a process called [[gluconeogenesis]]. The ability of the liver to release glucose into the blood from glycogenolysis is unique, since skeletal muscle, the other major glycogen reservoir, is incapable of doing so. Unlike skeletal muscle, liver cells contain the enzyme [[(glycogen-synthase-D) phosphatase|glycogen phosphatase]], which removes a phosphate group from glucose-6-P to release free glucose. In order for glucose to exit a cell membrane, the removal of this phosphate group is essential. Although gluconeogenesis is an important component of hepatic glucose output, it alone cannot sustain exercise. For this reason, when glycogen stores are depleted during exercise, glucose levels fall and fatigue sets in. Glucose disposal, the other side of the equation, is controlled by the uptake of glucose by the working skeletal muscles. During exercise, despite decreased [[insulin]] concentrations, muscle increases [[GLUT4]] translocation  and glucose uptake. The mechanism for increased GLUT4 translocation is an area of ongoing research.{{cn|date=April 2025}}

'''glucose control''':
As mentioned above, insulin secretion is reduced during exercise, and does not play a major role in maintaining normal blood glucose concentration during exercise, but its counter-regulatory hormones appear in increasing concentrations. Principle among these are [[glucagon]], [[epinephrine]], and [[growth hormone]]. All of these hormones stimulate liver (hepatic) glucose output, among other functions. For instance, both epinephrine and growth hormone also stimulate adipocyte lipase, which increases non-esterified fatty acid (NEFA) release. By oxidizing fatty acids, this spares glucose utilization and helps to maintain blood sugar level during exercise.{{cn|date=April 2025}}

'''Exercise for diabetes''':
Exercise is a particularly potent tool for glucose control in those who have [[diabetes mellitus]]. In a situation of elevated blood glucose ([[hyperglycemia]]), moderate exercise can induce greater glucose disposal than appearance, thereby decreasing total plasma glucose concentrations. As stated above, the mechanism for this glucose disposal is independent of insulin, which makes it particularly well-suited for people with diabetes. In addition, there appears to be an increase in sensitivity to insulin for approximately 12–24 hours post-exercise. This is particularly useful for those who have type II diabetes and are producing sufficient insulin but demonstrate peripheral resistance to insulin signaling. However, during extreme hyperglycemic episodes, people with diabetes should avoid exercise due to potential complications associated with [[ketoacidosis]]. Exercise could exacerbate ketoacidosis by increasing ketone synthesis in response to increased circulating NEFA's.{{cn|date=April 2025}}

Type II diabetes is also intricately linked to obesity, and there may be a connection between type II diabetes and how fat is stored within pancreatic, muscle, and liver cells. Likely due to this connection, weight loss from both exercise and diet tends to increase insulin sensitivity in the majority of people.<ref>{{Cite journal |last=Boutcher |first=Stephen H. |date=2011 |title=High-Intensity Intermittent Exercise and Fat Loss |journal=Journal of Obesity |language=en |volume=2011 |pages=868305 |doi=10.1155/2011/868305 |pmc=2991639 |pmid=21113312 |doi-access=free}}</ref> In some people, this effect can be particularly potent and can result in normal glucose control. Although nobody is technically cured of diabetes, individuals can live normal lives without the fear of diabetic complications; however, regain of weight would assuredly result in diabetes signs and symptoms.{{cn|date=April 2025}}