The momentum strategy is based on the idea that if there is enough force behind a price move, it will continue to move in the same direction. In other words, if a trend is well-established, it will likely continue as more traders and investors try not to miss out on the price move. The strategy takes advantage of investor herding mentality, also known as FOMO (fear of missing out), which drives the price in one direction.
To break it down a bit, when a stock reaches a higher price, it usually attracts more attention from traders and investors, which pushes the market price even higher. The price would continue to rise until something happens to make people start dumping the stock.
Once enough sellers are in the market, the momentum changes direction and forces the stock price down. Short-sellers would take advantage of the downside momentum to sell short and cover at a lower price.
Essentially, the momentum trading strategy seeks to take advantage of market volatility by taking short-term positions in stocks going up and selling them as soon as they show signs of going down. The investor then moves the capital to other stocks showing momentum. So, the market volatility is like waves in the ocean, with the momentum trader sailing up the crest of one, only to jump to the next wave before the first wave crashes down again.
It is important to note that momentum trading is not a long-only strategy. Some traders use a combination of both long and short approaches. Taking long positions in stocks with high upside momentum and short positions in stocks with a high downside momentum.