One of the most important standards that the API has set is the method used for measuring the density of petroleum. This standard is called the API gravity. Specific gravity is a ratio of the density of one substance to the density of a reference substance, usually water.
The most common symptoms of RSI include: 1  Pain. 2  Tingling. 3  A feeling of restlessness in the joint. 4  Weakness. 5  Throbbing. 6  Stiffness or cramp.
Repetitive strain injury (RSI) is a condition where pain and other symptoms occur in an area of the body which has done repetitive tasks. Repetitive strain injury (RSI) is a condition where pain and other symptoms occur in an area of the body which has done repetitive tasks.