In the faster-is-better world we live in, carving out 30 to 45 minutes a day for a good workout can seem like a major challenge—and that can totally mess with your quest for a strong core. Enter: the 7-minute workout.Impressive features of this ABS Workout- 7 minute workout- Supported by science- No equipment- 3 Levels: Beginner, Intermediate and Advanced- Each level has different exercise speed, depends on the level- Counting repetitions to keep track of your progress with voice and text- Daily Inspirational Quotes- Total calories burned- 2 languages: English and German- Beauty and Cool illustrationThis strategic, super-effective form of high-intensity circuit training is supported by science. To complement the original—and give you even more 7-minute options, we asked Yusuf Jeffers, certified personal trainer and Head Coach at Tone House in New York City, to create a companion abs workout that requires only your body weight.A killer combo of core-strengthening moves and cardio, this circuit’s designed to “attack” not only your abs and obliques, but also the muscles in your back, pelvic floor, and even your shoulders, says Jeffers. And, truth be told, it beats doing hundreds of crunches. “If you’re training for a sport—or just for everyday life—you usually don’t use any one muscle in isolation,” he says. “This correlates closer to actual, functional movements.” And that’s a good thing: While crunches certainly strengthen your abs, the body benefits more—by torching more calories, for example—from movements that recruit more than one muscle group.Though it’s important to remember that high-intensity interval training isn’t meant to be a daily workout, it’s a great tool to have in your exercise arsenal, particularly on days when all you’ve got is 7 minutes to spare.How to use this list: Perform each move below for 30 seconds, resting 5 to 10 seconds in-between. With this circuit, the goal is to go big or go home—meaning, working at the highest possible intensity for as many reps as you can without sacrificing form. Expect to perform anywhere from 15 to 20 reps, though remember that quality always tops quantity, says Jeffers. (So don’t stress if your rep count is on the lower end the first couple of times you try this—there’s always time to improve.) If time allows, you can repeat the circuit 2 to 3 times.