Sit-ups are a classic ab exercise, however, in order to break up the monotony of thousands of sit-ups, this at-home workout is designed as a fast-paced circuit. Sit-ups have gotten a bad rap because they tend to be hard on your back, says Harvard Health Publishing. But the exercises chosen are easier on the lower back and they target all of the abdominal muscles. Do all four exercises in a row with no break between. Your abs will be burning by the end of the workout.
Start with exercise No. 1 and progress, in order, through exercise No. 4, take a rest and then repeat the circuit two more times. Do each exercise for 30 seconds, completing as many repetitions as possible. Exercise scientist Dr. Len Kravitz writing for the University of New Mexico suggests working your abs three to five days a week, but a daily ab routine is completely OK.
The curl-up exercise works your abs harder than the standard sit-up, even though it's an abbreviation. Once your upper body gets more than halfway through a sit-up your hip flexors kick in to pull you the rest of the way up. When you use your hip flexors it means your abs are doing less work.
With the curl-up, the point is to roll up as far as your abs will let you, then go back down. This makes sure that most of the stress stays on your abs.
To do this exercise, start in a sit-up position with your arms straight by your sides. Slide your hands forward on the floor about 4 inches, or 10 centimeters, for maximal activation of your abs. Curl your head, neck and shoulders up as you reach forwards.
Keep going until your entire upper back is off of the ground, then slowly lower back down.
2. Cross-Body Sit-Up
This sit-up workout is known as the cross-body sit-up that involves a twisting motion, which means it activates the muscles at the sides of your abdomen known as the obliques.
Start by getting into a sit-up position, then pick up your right leg and cross it in front of your left knee. Then put your left hand behind your head. Reach your left elbow up and across your body towards your right knee. Get as close as possible to your knee, then go back down slowly.
For this exercise, you will do 15 seconds on the left and 15 on the right side, fitting in as many repetitions as possible.
3. Single-Leg Sit-Up
The single-leg sit-up looks almost identical to a regular sit-up. The only difference is that one is leg straight on the floor and the other leg is bent. The straight leg stops the hip flexors on that side from doing the work, leaving it all up to the abs. Thus, this version of the sit-up targets your abs even more than the traditional version.
Start by assuming a regular sit-up position but put your left leg out straight on the ground. Now perform a regular sit-up to your bent right knee. Try to use as little arm swing as possible.
Read more: 10 Core-Strengthening Kettlebell Moves
4. Kettlebell Sit-Up
The kettlebell sit-up is a tough exercise but it's totally worth it if you want a nice set of abs.
For this sit-up routine, you need a kettlebell or another easy-to-grip object. You can hold a gallon jug of water or milk or something round and heavy like a bowling ball. Grab the kettlebell with both hands and get into a sit-up position. Don't tuck your chin under too much, advises Muscle & Fitness. Now curl your shoulders and head off of the ground and slowly move the kettlebell down towards your legs.
Keep sitting up until you are at the top of the sit-up position. Try to keep the kettlebell as close to your chest as possible while you sit up. If you reach the kettlebell too far forwards the weight will help you sit all the way up instead of making your abs do all of the work.
Pull the kettlebell back towards your chest and slowly roll down the mat with your back. Keep your feet flat on the ground as you lower yourself. Keep pulling the kettlebell back towards your chest as you slowly roll all the way back to the ground.