GLUT4 is the major glucose transporter in muscle even in exercise. However, during exercise, it is translocated to the cell surface by contraction-triggered, insulin-independent mechanisms, such as AMP-activated protein kinase (AMPK) activation.

For more, you could read this review.

GLUT4 is the major glucose transporter in muscle even in exercise. However, during exercise, it is translocated to the cell surface by contraction-triggered, insulin-independent mechanisms, such as AMP-activated protein kinase (AMPK) activation.

For more, you could read this review.

Note:

'No insulin' is too strong a phrase; exercise and fasting are associated with low but detectable insulin levels. The reference range for fasting insulin in healthy individuals is $<174 \ \text{pmol L}^{-1}$ (contrast this with levels upto $1917 \ \text{pmol L}^{-1}$ one hour after glucose ingestion). Exercise studies have shown levels around $60-80 \ \text{pmol L}^{-1}$.

GLUT4 is the major glucose transporter in muscle even in exercise. However, during exercise, is translocated to the cell surface by contraction-triggered, insulin-independent mechanisms, such as AMP-activated protein kinase (AMPK) activation.

For more, you could read this review.

GLUT4 is the major glucose transporter in muscle even in exercise. However, during exercise, it is translocated to the cell surface by contraction-triggered, insulin-independent mechanisms, such as AMP-activated protein kinase (AMPK) activation.

For more, you could read this review.