Investors and traders can measure buying and selling interest by watching how many up or down days in a row occur and how their volume compares with days in which price moves in the opposite direction. Accumulation and distribution often LEAD price movement. In other words, stocks under accumulation often will rise some time after the buying begins. Alternatively, stocks under distribution will often fall some time after selling begins. It takes volume for a stock to rise but it can fall of its own weight.
Rallies require the enthusiastic participation of the crowd.
When a rally runs out of new participants, a stock can easily fall. Liquid stocks are very easy for traders to buy and sell. Stock chart analysis does not work well on illiquid stocks. Breakouts accompanied by volume much higher than the average for that stock are healthy for the continuation of the price movement in that direction. During these days, the last of the buyers or sellers take positions.