Martin Rooney’s 12-week diet and exercise program uses the language of combat — and models that look like ultimate fighters — to show you how to get that fierce, toned-up look, or at least a trimmer you. According to Rooney, the most effective way to burn fat and build muscle is interval training: sprints, free-weight circuits and exercises using your own body weight, such as push-ups interspersed with claps. His program also includes a nutritional plan focused on a healthful balance of protein, vegetables, fruit and whole grains, complete with recipes. If you are intrigued by the science behind his plan, Rooney offers a primer on aerobic exercise, anaerobic exercise and adenosine triphosphate, or ATP, a molecule central to metabolism. For those more interested in just working out, there are lots of pictures. Each exercise — from the mini plyo hop (small, quick hops performed in a pattern similar to hopscotch) to the Zercher lunge (performed with a barbell in the crooks of your elbows) — is broken down and demonstrated by some very buff guys. The program is geared toward men, but that doesn’t mean women can’t unearth their inner warriors just as well.