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.
OI is highly variable, and signs and symptoms range from mild to severe. In addition to broken. bones (fractures), people with OI sometimes have muscle weakness or joint laxity (loose joints). They often have. skeletal deformities including short stature, scoliosis (curvature of the spine) and bowing of long bones.