When you think of core exercises, crunches and planks probably come to mind—and for good reason. You can do them anytime, anywhere, with no equipment or gym membership required.
Both of these moves offer benefits, but which one will really give you stronger, more defined abs? We asked two fitness experts to weigh in.
When it comes to strength (not definition), both experts agree that planks take the win.
Planks involve no movement; instead, they require you to contract your core and glutes to hold a static position against gravity.
In doing so, planks “fire up” the transverse abdominis—the deepest layer of your abs—“and activate the entire core from every angle,” said Noam Tamir, CSCS, founder and CEO of TS Fitness in New York City.
Their ability to engage muscles in this 360-degree fashion, as Tamir put it, is what makes planks superior in building core strength.
As a result, regular planking can help with everything from everyday activities to sports performance, said Or Artzi, CPT, a lead group fitness instructor at Equinox and creator of the fitness platform Orriors. It can also support balance and may ease lower back pain, research suggests.
Meanwhile, crunches—which involve bending your spine forward—work the hip flexors, lower back, and parts of the abs, including the transverse abdominis and obliques (the muscles on each side of your abdomen), according to Tamir.
But the key difference, Tamir said, is that crunches mainly target the rectus abdominis, aka the classic “six-pack” muscle. Unlike planks, “crunches mostly focus on the surface-level abs,” he explained.
The upside of focusing on the surface over the deepest abdominal muscles is that a regular crunch routine is more likely to deliver that defined six-pack—especially when paired with resistance, such as dumbbells or plates, according to both experts.
“Repeated spinal flexion creates direct tension and mechanical loading on this muscle, stimulating growth,” Artzi said. That’s not the case with planks, which involve muscle contraction but no movement, Tamir added.
Keep in mind, however, that proper nutrition plays just as important a role in getting chiseled abs as targeted exercise does, Artzi pointed out.
Although planks may be better for building deeper strength and power, crunches are still a valuable way to develop ab strength—and can help you achieve the definition you may be seeking.
That’s why Artzi recommends incorporating both into your exercise routine if you can. “If tolerated without discomfort, [crunches] complement planks,” she said.
A proper crunch involves lying on your back with your knees bent and feet flat. Place your hands across your chest or behind your head, engage your core, and lift your head, neck, and shoulders—keeping your lower back on the floor.
To do a plank, start on hands and knees, wrists under shoulders. Step your feet back and form a straight line from shoulders to heels—all while activating your abs.
Once you’ve nailed down proper form, increasing the difficulty can further boost core strength and stability. For planks, the International Sports Sciences Association recommends variations like side planks, weighted planks, walking planks, or lifting one arm and/or leg at a time.
As for crunches, you can make them harder by adding a stability ball or trying variations like decline crunches or captain’s chair crunches, according to the American Council on Exercise.
