While Federal Reserve Chair Janet Yellen is the one tasked with delivering a message over the next two days when she speaks to Congress, financial markets are keen to know if she has absorbed their message to her: stifle your rate hike plans. In the 52 days since investors last heard from Yellen, when she held a press conference after overseeing the first U.S. interest rate hike in nearly a decade, markets have been roiled with volatility and increasing doubt about the health of the U.S. and global economies.