Palpitation is an awareness of the abnormal beating of the heart. It may occur in people with or without heart problems. Heart palpitations when lying down is not a common occurrence and can be caused by various factors.
Flat feet occur when the normal foot arches have partially or completely collapsed. When the foot is put to the ground the inner or middle side of the foot comes down to the floor rather than remaining raised. This can cause the whole foot to roll inwards (this is called over-pronation).
When the lateral hamstrings are stronger than the medial hamstrings, the popliteus muscle will weaken. Overpronation or running in worn shoes will cause excessive lower leg rotation and overstress the popliteus. A common practice among runners is hanging out or walking around in old running shoes.