NEW YORK ( TheStreet) -- When the stock market crashed in 2008, most target-retirement mutual funds sank. That was a painful blow for investors who had viewed the funds as relatively safe retirement vehicles. Congressional critics called for changing the funds.Now some managers are taking steps to ensure that their funds prove more resilient in difficult markets. Major fund companies that have introduced new risk-control approaches include Alliance Bernstein ( AB), Invesco AIM and Putnam Investments. It is too soon to know how effective the risk strategies will be. But they represent innovative steps that challenge long-held tenets of investing. If the new systems succeed, they could encourage broad changes in target funds. The target funds are designed for people who plan to retire in certain years, such as 2020 or 2030. As the retirement date approaches, the funds automatically become more conservative, shifting assets from stocks to bonds. Say a young person selects a 2050 fund. In the typical approach, the fund would begin with as much as 90% of assets in stocks. As the retirement date approaches, the allocation to stocks would fall year by year until it hit 50% or less. To protect assets, Invesco AIM has scrapped many of the traditional elements of target funds. Instead of holding mainly stocks, AIM Balanced-Risk Retirement Funds emphasize other assets. Under normal conditions when no asset class seems particularly cheap, the funds keep 90% of assets in bonds, 30% in stocks and 30% in commodities. The numbers add up to more than 100% because the portfolios hold futures, which can be leveraged to increase the total exposure to each asset class. Because of the big bond stake, the AIM funds could lag in stock bull markets. But the managers argue that they should protect assets in bad times and enable investors to obtain consistent results. "By avoiding serious losses in downturns, we can achieve attractive long-term returns," says Scott Wolle, manager of AIM Balanced-Risk Retirement Funds. The AIM funds hold their same asset allocation until 10 years before the retirement date. Then the funds begin gradually shifting to cash. At retirement, 40% of assets would be in cash with the rest in stocks, bonds and commodities.