The Organs of your body have their sensory touches at the bottom of your foot, if you massage these points you will find relief from aches and pains as you can see the heart is on the left foot.
Typically they are shown as points and arrows to show which organ it connects to.
It is indeed correct since the nerves connected to these organs terminate here.
This is covered in great details in Acupressure studies or textbooks.
God created our body so well that he thought of even this. He made us walk so that we will always be pressing these pressure points and thus keeping these organs activated at all times. God is Good and a great Provider!