Few pundits would have predicted that the long-term bull-market trend in the U.S. stock market that started in March of 2009 would be such a surprisingly steady and profitable ride. And yet buy-and-hold investors who followed the trend and bought an S&P 500 Index fund have generated gains of 88.71% over the past five years. Equally surprising is that betting on trends in any asset class other than the U.S. stock market hasn't worked very well for Wall Street's "smart money." That's been especially true for commodity trading advisers (CTAs), who include among their ranks some of the most sophisticated trend following investors on the planet. The mysterious world of CTA investing CTAs invest in managed futures. That means they follow the trends in the commodities, currencies and fixed-income markets, relying on often-complex mathematical formulas to make their investment decisions. Yet, the relative lack of volatility in global financial markets — and the breakdown of the conventional relationships between commodities, currencies, equities and bonds wrought by quantitative easing — had put a wrench in the works of the quant jocks working at the world's top CTAs. But the recent plunge in crude-oil prices, a rising U.S. dollar and the tumbling Japanese yen and euro may have changed all that. After a long absence, long sustainable trends in the commodity and currency space are back. No wonder CTAs had their best month in over a decade in November and have put CTAs back on track for a terrific 2014. Building your own CTA trend-following portfolio The recent emergence of sustained trends is bringing good old-fashioned trend following investing back into favor. The good news is that you can follow the same trends as the CTAs to generate robust gains via several specialized exchange-traded funds (ETFs) that don't require complex algorithms or sophisticated computer models to understand. By far the most popular choice for riding the trend lower in crude oil is theProShares UltraShort Bloomberg Crude Oil SCO, -4.69% This ETF is designed to deliver twice the inverse of the Dow Jones-UBS Crude Oil Sub-index. In essence, when crude oil prices fall 2% in a day, then SCO should rise about 4%. Over the past six months, SCO has ridden the trend of falling oil prices higher by more than 199.83%. It surged 71.44% just this past month. Another recent big drop in crude oil prices sent SCO up 21.98% in just a single week. A rising U.S. dollar also has been a favorite for trend followers. Although CTAs have the ability to leverage currency trades by as much as 20:1, thereby magnifying their gains substantially, you too can profit from the surging greenback through the PowerShares DB US Dollar Index Bullish FundUUP, -0.04% This ETF follows the U.S. Dollar Index, which in turn tracks the value of the dollar relative to a basket of the six major world currencies — the euro, Japanese yen, British pound, Canadian dollar, Swedish krona and Swiss franc. During the prior six months, UUP has captured the trend higher in the buck nicely, as the fund is up a solid 9.64%. The bottom line? There are plenty of other ways to profit from emerging strong trends. Just think of the collapsing Japanese yen and Russian ruble. And that means that after several long years in the investment wilderness, trend following is back, Disclosure: Vardy recommended UUP in one of his newsletters.