If the stock market has been a roller coaster ride, 401(k) plan participants are keeping their hands and feet in the cars, say major plan administrators and record keepers. Principal Financial Group Inc. said that 6,406 of the 2.4 million participants in plans that it administers made transfers on Aug. 8, more than three times the 2,000 participants who make a transaction on a typical day. Still, just 0.25 percent of plan participants took action that day, when the Dow Jones Industrial Average lost 5.5 percent. Wells Fargo Institutional Retirement and Trust reported about $1 billion flowed into stable-value funds between Aug. 1 and Aug. 15, less than 1 percent of the $164 billion in plan assets, exclusive of defined-benefit plans, which Wells Fargo administers.