What role does the sympathetic nervous system play in metabolism during exercise?

The sympathetic nervous system plays a critical role in the body’s response to exercise, primarily by enhancing energy expenditure and mobilizing energy sources. This system is responsible for the "fight or flight" response, which prepares the body for increased physical demands.

During exercise, activation of the sympathetic nervous system leads to various physiological changes that support enhanced performance. These include an increase in heart rate and cardiac output, vasodilation of blood vessels supplying active muscles, and the release of adrenaline (epinephrine). Adrenaline stimulates glycogenolysis, the breakdown of glycogen into glucose, in the liver and muscles, increasing the availability of glucose for energy production. It also promotes lipolysis, the breakdown of fat stores for energy, which contributes to greater energy availability.

In essence, by mobilizing glucose and fat stores and increasing energy expenditure, the sympathetic nervous system effectively enhances the body’s capacity to perform physical activities, making it integral to exercise metabolism. The other options do not align with the sympathetic nervous system’s primary functions during exercise, which focus on increasing energy availability and expenditure rather than inducing relaxation or decreasing heart rate or glucose availability.