1] Mountain Climbers (30 seconds)
Drop into push-up position and, while maintaining a rigid torso, bring one knee into your waist and then begin alternating between feet as quickly as possible. It's akin to running while in push-up position. You should strive to take your back leg to full extension and your front leg pulled high to your chest on each stride in order to maximally engage your abs. Get in as many "strides" as you can in 30 seconds then move, without rest, to the next exercise.
2] Bicycle Crunch (30 seconds)
A forgotten move among the crunch-heavy masses, the bicycle crunch has been shown to trigger the most
muscle activation throughout r
ectus abdominis and obliques. Lie flat on your back with your hands lightly touching your head. Raise your feet 6-12 inches off of the floor. Curl up as high as you can, bringing your shoulder blades off the ground, simultaneously trying to bring your right elbow across your body toward your left knee. Alternate sides as fast as you can with clean form for 30 seconds. Without rest, move to the next exercise.
3] Double crunch (15 reps)
The 10-15 reps of the double crunch you usually aim for become a different beast after 60 seconds of heavy core engagement. Lie down on the floor with your legs straight, feet together. Place your hands gently behind your head and raise your feet off the floor roughly six inches. Crunch your upper body off the floor while simultaneously bringing your knees toward your torso, so that your upper body meets your lower body in the middle. Squeeze and return to the start, allowing your legs to remain above the floor throughout. After 15 reps, flip over into plank position.
4] Plank (30 seconds)
If you're someone who brags about how long you can hold a plank, we're glad that you've taken on this routine. As a first or second exercise, the plank can make most gym rats look like superheroes. But after several other exercises ahead of it, the entire core is abnormally fatigued. And because of the absence of rest periods and the types of exercises listed here, 30 seconds will be sufficient to cap off your abs here.