If you have seven minutes...try the routine that is basically excuse-proof.
The "scientific seven-minute workout" that appeared in the May–June issue of the American College of Sports Medicine’s Health & Fitness Journal (and then in The New York Times) has a lot going for it: It's fast, it's easy, it works your entire body and doesn't require any extra equipment. You can do it while you're waiting for pasta to cook or for your iron to heat up. That's why it almost immediately became one of the most popular workouts in the country, inspiring dozens of smartphone apps and countless derivative routines. However, the seven-minute workout comes with an important and underreported caveat: The researchers who developed this routine intended it to be repeated three times in a row—making it more of a 21-minute workout. But they agree that one round is better than none. You'll still get significant calorie burning and muscle-building benefits, especially if you're doing this on your "off days" (i.e., sandwiched between a yoga day and a swim day).