Frontal axis: imaginary line that is running from the side in the frontal plane. Movement in the sagittal plane is around the frontal axis of rotation. For example during flexion and extension of elbow, it is actually rotating around the frontal axis.
Sagittal axis: it passes horizontally from posterior to anterior and is formed by the intersection of the sagittal and transverse planes. It intersects the frontal plane at a right angle.
Longitudinal axis: it passes vertically from inferior to superior and is formed by the intersection of the sagittal and frontal planes. Movement on the transverse plane take place on the axis e.g. gymnast performing a full spin.
