You are being treated for heartburn or hiatal hernia, and you feel sudden chest or stomach pain, have difficulty swallowing, are vomiting, or are unable to have a bowel movement or pass gas; you may have a hernia that has become obstructed or strangulated, which are emergencies.
One strong possibility for your symptom is gall bladder stones and cholesterol deposits within the gall bladder which can cause sharp pain. Getting an ultrasound of the upper abdomen done in a walk in clinic or the ER will confirm the diagnosis.
When using either the seated or lying leg curl machine, the muscles on the back of the thigh will contract to bend your knee. The hamstrings are made of three muscles -- the biceps femoris, the semimembranosus and the semitendinosus. The largest of the three is the biceps femoris.