The frontal line is in two parts.
Part One – runs from the top of the toes, over the ankle, along the front of the shin, over the knee and via the very large and powerful quadracep muscles attaches to the front of the pelvis.
Part Two – runs from the pubis bone and travels up to the neck muscles connected to the collar bone. The muscles involved includes the abdominals, the muscles around your sternum, and the strongest of the neck muscles.
Commonly tension in the frontal line will be due to poor posture where the person appears hunched over.