In trading on Friday, shares of the Proshares Short High Yield ETF ( SJB) entered into oversold territory, changing hands as low as $28.49 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of Proshares Short High Yield, the RSI reading has hit 29.0 — by comparison, the RSI reading for the S&P 500 is currently 65.8. A bullish investor could look at SJB's 29.0 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), SJB's low point in its 52 week range is $28.49 per share, with $34.00 as the 52 week high point — that compares with a last trade of $28.49. Proshares Short High Yield shares are currently trading off about 0.1% on the day.