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.
Print this page. Repetitive strain injury (RSI) is a general term used to describe the pain felt in muscles, nerves and tendons caused by repetitive movement and overuse.It's also called work-related upper limb disorder or non-specific upper limb pain.SI can be divided into two types. Type I is when the pain is the result of a specific medical condition, such as carpal tunnel syndrome or tennis elbow. Type II is when no specific cause can be found and is often referred to as non-specific upper limb pain.