The indicator of Inertia is taken from the physics realm. It describes the phenomena of continuous motion of the body until an outside force acts upon it. The momentum of a stock that is based upon its volatility is measured by the Inertia here. Inertia is a smoothed RVI, as an outgrowth of Donald Dorsey's Relative Volatility Index. It was the September 1995 issue of Technical Analysis of Stocks and Commodities where Dorsey introduced the idea of Inertia.
The basic usage of the Inertia indicator is measuring a momentum of a currency-trading price based on its volatility. Inertia is a smoothed RVI, as an outgrowth of Relative Volatility Index.
A scale that Inertia is measured on is from 0 to 100. If the indicator is below 50, the Inertia is seen to be negative. Positive Inertia is supposed to have the indicator above 50. Positive inertia signs show a long-term upward trend whether long-term downtrends are indicated by negative Inertia.