Question

Following several weeks of endurance exercise training, the capacity to transport glucose into skeletal muscle fibers is increased. Which of the following training-induced changes contribute to this training effect?

a. an increase in mitochondria within muscle fibers
b. the increase in the number of GLUT4 glucose transporters
c. an increase in circulating catecholamines
d. a decrease in circulating insulin

Answer 1

The increase in GLUT4 glucose transporters contributes to the training effect of increasing glucose transport into muscle fibers. Insulin activates a receptor that facilitates the movement of GLUT4 transporters to the cell membrane.

Step-by-step explanation:

The increase in the number of GLUT4 glucose transporters contributes to the training effect of increasing the capacity to transport glucose into skeletal muscle fibers. Insulin plays a key role in facilitating glucose uptake by activating a tyrosine kinase receptor, which triggers the movement of intracellular vesicles containing GLUT4 transporters to the cell membrane. This allows glucose to move into the muscle cells and be used for energy.

In contrast, the other options mentioned (a decrease in circulating insulin, an increase in mitochondria within muscle fibers, and an increase in circulating catecholamines) are not directly involved in the training-induced increase in glucose transport.