Crunches and sit-ups are popular exercises to add into an abs workout. Some runners swear by these traditional moves because practicing them regularly can help you build a strong core—which is a major factor when it comes to power, speed, and stability out on the roads and trails—without any equipment. But the key to practicing any variation of a crunch or sit-up is to know the difference between each move and to perform these moves correctly.

“The difference between the crunch and the sit-up has largely to do with the range of motion,” Noam Tamir, C.S.C.S., tells Runner’s World. “A crunch is going to be a smaller motion. It’s also going to be a lot easier than a sit-up. The sit-up is more challenging, so it will challenge you more, but it does have more risk involved for people that are susceptible to injury.” (Sit-ups may lead to feelings of discomfort in your lower back.)

In the workout below, Tamir demonstrates different variations of the crunch and the sit-up, including how to do both traditional moves properly. He says practicing cross-body exercises like the cross-body crunch, bicycle crunch, and sprinter sit-up will strengthen your obliques to help with the locomotive movement of running.

How to do it: You will need an exercise mat for this workout. Perform each move in the first circuit for the number of reps listed below, resting 15 seconds between each exercise. Complete 1 to 3 rounds of the first circuit before moving on to the second circuit. Then, perform each move in the second circuit for the number of reps listed below, resting 15 seconds between each exercise. Complete 1 to 3 rounds of the second circuit. Alternatively, you can consider adding a few moves from this list into your weekly routine.

Circuit 1

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Sit-Up

Lie face-up with your knees bent, feet flat on the mat, and fingertips behind your ears. Engage your core muscles to sit up so that your shoulders are directly above your hips. Slowly return to the starting position. Perform 10 to 12 reps.

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Cross-Body Crunch

Lie face-up with your knees bent and your feet flat on the mat. Place your fingertips of your right hand behind your right ear and place your left hand out by your side or wherever you feel comfortable. Perform a crunch, and drive your left knee up to meet your right elbow while keeping your core engaged. Return to starting position, and repeat for 10 to 12 reps. You can either complete on the opposite side right away or switch sides during the next circuit.

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Sprinter Sit-Up

Lie face-up on the mat with your legs straight out and your arms by your sides. Engage your core to sit up while driving your right arm forward and bringing your left leg to your chest. Return to the starting position, and repeat, alternating sides. Complete 10 to 12 reps.

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Circuit 2

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Crunch

Lie face-up on the mat with your knees bent and your feet flat on the floor. Place fingertips behind ears—avoid interlocking fingers because this can lead to straining your neck. Engage core and keep chin up as you lift shoulders and upper back off the mat then lie back down. Repeat 10 to 12 reps.

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Single-Leg Sit-Up

Lie face-up on the mat with your left knee bent, your right leg straight out and your arms straight by your ears. Engage your core to lift your shoulders, chest, and back off the mat. Your arms will now be straight out in front of you. Lie back down to starting position. Repeat 10 to 12 reps. You can either complete on the opposite side right away or switch sides during the next circuit.

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Bicycle Crunch

Lie face-up with both hands behind head, legs bent, and feet flat on floor. Lift right shoulder off mat to bring right elbow toward left knee, while extending right leg straight. Reverse to draw left elbow to right knee as you extend left leg straight. Repeat 15 to 20 reps, alternating legs and elbows.

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