A weakness of the valve between the stomach and oesophagus (food pipe) can cause a reflux of the acid from the stomach to the lower part of the oesophagus. This gastro-oesophageal reflux can cause heart-burn. Sometimes, a heavy meal or increase in intra-abdominal pressure such as while straining or lifting weights, can bring about this reflux. Excess acid secretion can also cause acidity and ulcers, when the normal protective lining of the stomach and duodenum (the part of the intestine that joins the stomach), is damaged. The resulting ulcer is called gastric ulcer if it is in the stomach and duodenal ulcer if it is in the duodenum.