WINDERMERE, Fla. ( Stockpickr) -- Professional traders running mutual funds and hedge funds don't just look at a stock's price moves; they also track big changes in volume activity. Often when above-average volume moves into an equity, it precedes a large spike in volatility.Major moves in volume can signal unusual activity, such as insider buying or selling -- or buying or selling by "superinvestors." >>5 Huge Stocks Ready to Rocket Higher Unusual volume can also be a major signal that hedge funds and momentum traders are piling into a stock ahead of a catalyst. These types of traders like to get in well before a large spike, so it's always a smart move to monitor unusual volume. That said, remember to combine trend and price action with unusual volume. Put them all together to help you decipher the next big trend for any stock. With that in mind, let's take a look at several stocks rising on unusual volume today. >>5 Hidden Earnings Bargains Worth Buying Now Merck Merck ( MRK) is a global health care company that delivers innovative health solutions through its prescription medicines, vaccines, biologic therapies, animal health and consumer care products. This stock is trading up 2.3% at $45.97 in recent trading. Today's Volume: 17.19 million Average Volume: 16.48 million Volume % Change: 77% From a technical perspective, MRK is spiking higher here and breaking out above some near-term overhead resistance at $44.99 with above-average volume. This stock has been uptrending strong for the last two months, with shares moving higher from its low of $40.44 to its intraday high of $46.16. During that move, shares of MRK have been mostly making higher lows and higher highs, which is bullish technical price action. That move is now pushing shares of MRK within range of triggering a major breakout trade. That trade will hit if MRK manages to take out some past resistance levels at $47.09 to $48 with high volume. Traders should now look for long-biased trades in MRK as long as it's trending above $44.99 or $44 and then once it sustains a move or close above those breakout levels with volume that hits near or above 16.48 million shares. If that breakout triggers soon, then MRK will set up to enter new 52-week-high territory above $48, which is bullish technical price action. Some possible upside targets off that breakout are $50 to $52.