So with these guidelines in mind, the answer to your question depends on your exercise goals.

CNN: Is a shorter but harder workout better?

In the face of all these challenges, we're going to have to answer a central question as a nation: What, if anything, can we do to restore a sense of security for people who are willing to work hard and act responsibly in this country?

WHITEHOUSE: President Obama Speaks at the Associated Press Luncheon