NEW YORK ( TheStreet) -- The credit crisis dragged down not only stocks but also corporate bonds, precious metals and real estate. Government debt, a haven for the most conservative investors, was spared.Investors were shocked to see that their diversification plans failed to provide protection. The downturn revealed a difficult reality: Under extreme conditions, most investments move in the same direction. But there were a few mutual funds that proved resilient. Those investments aren't correlated with stocks or bonds. When the stock market sinks again, you can bet that uncorrelated funds won't move in lockstep with other investments. As the stock-market rally picks up steam, it may be worth considering such funds before prices get out of control. Four Risks That Can Ruin Retirement (Forbes) Still, the resilient funds don't make money every year. Some sell short or use other techniques that can lag behind during bull markets. Still, it could be worth putting a small portion of assets into such mutual funds. One of the heroes of the downturn was Rydex/SGI Managed Futures Strategy ( RYMTX). While the S&P 500 Index lost 37% of its value during 2008, Rydex/SGI made 8.5% for the year. The gain is particularly noteworthy because the mutual fund invests in commodities, which recorded huge losses. Rydex/SGI stayed in the black because it sometimes takes short positions, betting that prices will fall. The mutual fund tracks the S&P Diversified Trend Indicator, a benchmark that follows 14 kinds of commodities, including livestock, industrial metals and currencies. To calculate the benchmark, S&P checks the spot price of each commodity once a month. If the price is above the average of recent months, the indicator takes a long position in the futures of the commodity. If the spot price is below the average, S&P goes short. Commodity trend following has long been used by hedge funds. The strategy is based on the idea that once a commodity begins moving down or up, it tends to stay in that pattern for some time. Since S&P began operating the index in 2004, the benchmark has mostly delivered annual returns in the high single digits or low double digits. But the approach works best when there are sharp moves. That happened in 2008 when there were big up-and-down shifts in currencies, gold and oil. In 2009, there were no consistent trends, and the benchmark recorded a loss.