Sit-ups. Crunches. You know that both of these moves are supposed to somehow strengthen your core since they're both abs exercises. But what's the true difference between the two? Aren't they kiiinda the same thing? As it turns out, they're not. (And if you didn't know this, you're not alone!) "The main difference between the two is that unlike a sit-up, in a crunch, the lower back never leaves the floor," explains Katharine Glazer, CPT.
With the sit-up, by raising your torso off the ground, you're targeting multiple muscle groups at once, such as your hip flexors, rectus abdominis (a.k.a. six-pack abs muscles), transverse abdominis (deep core muscles), obliques (side abs), and lower-back muscles. The crunch, on the other hand, is an isolated exercise that only targets your rectus abdominis (primarily your upper six-pack), she says.
When it comes to which exercise is "better" for you, this depends on the muscle you're targeting, Glazer explains. Start by answering a couple questions: Are you looking to get the most bang for your buck and work multiple muscle groups at once, or are you looking for intense muscle isolation? If it's the former, sit-ups are few you. The latter? Crunches could be your jam. "Every body has unique demands and requirements, there is no one size fits all," says Glazer.
That said, it wouldn't hurt if we got a liiittle bit more specific. Keep reading for the pros and cons of both sit-ups and crunches, according to experts.
Pros: You're working with *multiple* muscle groups
So yeah, sit-ups help you sculpt your abs (and more!) from lots of angles at once when done with proper form, says Olivia Amato, CPT, a Peloton instructor.
If you're looking to work on your stabilization, sit-ups are def for you. Why? Lifting your whole torso from the ground engages your balance-focused muscles like your abs, hip flexors, legs, back, and neck, Glazer explains.
A bonus? Working those stabilizing muscle also helps improve your posture, Amato adds.
Cons: There's greater risk of injury
While doing sit-ups helps build muscle, there is an increased risk of injury when incorporating them into your exercise routine. "The problem with sit-ups is that it’s very difficult to do the exercise correctly without rounding the lower back, which increases stress on the lumbar spine," explains Glazer. For this reason, "trainers tend to have their clients avoid sit-ups to decrease the risk of injury," she says.
How To Do A Proper Sit-up
"Lie on your back with knees bent at 90 degrees and feet flat on the floor," Glazer explains. "Place your fingertips on the back of your ears, elbows bent and pointing out to the side." Then, take a deep breath in, contract your core muscles, and lift your torso off the ground as you exhale, continuing until your chest is as close to your thighs as possible. (Though if you don't make it all the way there, no worries!)
With a smooth and steady motion, inhale as you return to the starting position. Got it? Great. Start with 10 reps and add as you feel more confident!
Sit-up hack: "I love doing sit-ups when I have a table to anchor my feet on or a workout buddy holding my feet down with their hands," says Amato. "This usually ensures proper form because you don't have to worry about keeping your feet on the ground on top of everything else."
Pros: They're veeery simple
Crunches really help define and isolate the upper abdominals and are great when aiming for high rep counts, says Amato. "I find that crunches are a move I can do continuously because they're a simple, low-impact exercise," she explains. "With crunches, you just need to focus on lifting your head and shoulders off of the floor while supporting your neck, so it's easier to get the move down and perform without feeling muscle pain."
Cons: They *only* target your abdominals
Crunches are super beneficial when it comes to sculpting the top of your six-pack, but that's actually *also* their downfall.
"The problem with crunches is that since the hips and legs are stationary, you’re not fully activating the lower abdominals, nor or you engaging the obliques," Glazer explains. "If you’re looking to strengthen your entire core, there are a plethora of other exercises that’ll give you a greater return." (*cough*, best abs exercises, *cough*)
And PSA: You can also experience neck pain if you strain and overextend your neck muscles while doing a crunch, Amato says. "Make sure to be aware of that and keep the work in the core, not the neck," she notes. Do this by keeping your chin tucked, but not touching your chest, and avoid pulling your neck up with your hands. Instead, make it as heavy as possible in your palms to put more work into your abs.
How To Do A Proper Crunch
Similar to a full-on sit-up, to perform a crunch, all you need to do is lie on your back with knees bent at a 90 degree angle, keeping your feet flat on the floor, Glazer explains.
"Place your fingertips on the back of your ears, elbows bent and pointing out to the side. Take a deep breath in, contract your core muscles, and then lift only your head and shoulder blades from the ground, exhaling as you rise. Inhale as you lower to starting position," Glazer says. Start with 10 reps and, if you feel like you've got the hang of things, keep goin' for 20 to 30.
Crunch hack: "Crunches can sometimes feel repetitive, but I find that when they do, I just add a twist—pointing one elbow toward opposite knee—to spice things up or crunch to the beat of a song," Amato says. Noted!
Conclusion: Sit-ups and crunches are each beneficial in their own ways.
Both can help you build abdominal strength, and each exercise comes with its own set of pros and cons. Assess which might be best for your skill level and safety, then get to work. Start slow and, most importantly, have fun!
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