How to Do Crunches: Form Tips and Variations

When's the last time you did crunches? With countless core machines and ab-training programmes available today, you may wonder whether this classic move still deserves a place in your routine. The answer is yes, trainers stand by crunches because they're a foundational movement that helps build core strength and improve abdominal engagement at any fitness level.

"Crunches can absolutely be a solid core exercise, especially when you do them with intention and with good form", says Phillip Solomon, NASM-certified personal trainer and Barry's instructor. "They're simple, accessible and they teach you how to actually activate your abs instead of letting your low back or hip flexors do the heavy lifting during your workout".

Ahead, learn how to do crunches so you get the most out of the exercise, plus variations that strengthen different parts of your core.

"While crunches are often dismissed as 'just an ab exercise', they're actually a very effective move to target a key muscle of the core: the rectus abdominis", says Cori Lefkowith, NASM-CPT, CES, FNS, PES, founder and head coach of Redefining Strength and author of The STRONG System: Transform Your Mindset and Build Your Best Body at Any Age.

The rectus abdominis is also referred to as your "six-pack" muscles. They're responsible for spinal flexion or when you bend your spine forward and round your back.

"These muscles not only help control your spine during running, lifting, carrying, and rotational movements, but also prevent your hip flexors and lower back from taking on extra work and risking injury", explains Solomon.

Not only can crunches enhance your athletic performance on the track and in the gym, but they also make everyday movements, like walking on uneven terrain or sitting upright in a chair for long periods, feel easier. The top benefits of crunches include:

• Improved core stability. "Strong abs help control ribcage and pelvic positioning to improve your posture and reduce excessive spinal extension during lifting and running", Lefkowith says.
• Enhances balance and coordination. When your rectus abdominis and accompanying ab muscles are strong, they improve torso control, which supports acceleration, deceleration, agility and quick directional changes, Lefkowith explains.
• Builds mind-muscle connection. Your mind and body are more connected than you may realise. "Crunches teach you how to actually feel and isolate your abs so future movements become stronger and more intentional", Solomon says.
• Improves ab strength and definition. "Crunches train the abs through their full range of motion, helping develop strength and muscle definition", Lefkowith says.
• Supports better breathing mechanics. Strengthening your abs improves ribcage control and helps you manage intra-abdominal pressure more efficiently, which can support smoother breathing during running, lifting or high-intensity training, Lefkowith explains. However, crunches are just one tool. Research suggests that integrating core work with diaphragmatic breathing may enhance respiratory function and abdominal strength more than traditional ab exercises alone.
• Reduces risk of overuse injuries. When your core muscles are strong, your hips and lower back don't have to take on as much load, which helps ease pressure on these areas during long runs or endurance sessions, Solomon explains.

As with any strengthening movement, your technique matters—not only for maximising the benefits of the exercise but also for preventing surrounding muscles and joints from taking on unnecessary stress.

"Even small adjustments, like keeping a posterior pelvic tilt or rolling up one vertebra at a time, can dramatically increase abdominal activation", Lefkowith explains. "These form cues help make sure the abs do the work instead of the neck, hip flexors or lower back, which not only improves your results but also reduces the risk of discomfort or injury".

Follow these cues from Lefkowith and Solomon to get the most out of a standard crunch and keep the work where it belongs—your core muscles.

1. Lie on your back with your knees bent and feet flat on the floor (or lift your legs into a tabletop position if you're more advanced).
2. Place your hands behind your head with your elbows wide and gently press your head back into your hands to avoid tucking your chin.
3. Press your lower back towards the floor and draw your pelvis slightly towards your ribs to engage your abs.
4. Exhale and lift your shoulder blades off the ground, rolling up one vertebra at a time using your abdominal muscles—not your neck.
5. Pause at the top and maintain engagement through your midsection.
6. Inhale as you slowly lower back down with control, rolling down one vertebra at a time and keeping your pelvis slightly tucked.

While there's more than one way to do a crunch, using suboptimal technique can limit the exercise's effectiveness and cause unnecessary strain. Below are common mistakes—and how to avoid them—with tips from Lefkowith and Solomon.

• Rushing through reps. When you move too quickly, momentum takes over, meaning your abs do less work, Lefkowith explains. Slow, controlled movements are the name of the game with crunches. "I love to advise clients to use a 1-2-3 method for timing", Solomon says. "To do this, lift off the ground in one count, hold for two counts and slowly release your shoulders back to the ground for three counts".
• Straining your neck. "Tucking your chin pulls the work out of your abs", Lefkowith says. "To help avoid your neck from engaging, press your head gently into your hands and focus on rolling up to lift your shoulder blades off the ground". Another helpful cue: look up toward the sky, Solomon adds. "The space between your chin and chest should be about the size of your fist".
• Using your hip flexors and lower-back muscles. If you feel discomfort in your hip flexors (front of hip muscles), that's usually a sign you're relying on these muscles, plus those in your lower back, instead of your rectus abdominis muscles, Solomon says. You can easily tweak this by lying flat on your back, pulling your ribs down, and as you exhale, "imagine pulling the abdominal wall back towards the spine", Solomon says. "As you leave the ground, keep the elbows, shoulders and chest spread as wide as possible, ensuring that there is no weight on the top of the vertebrae".
• Turning the crunch into a sit-up. "Coming up too high and performing a sit-up will also engage your hip flexors more", Lefkowith says. To engage your abs, lift just until your shoulder blades are about to leave the floor and think about drawing your ribs toward your pelvis, she notes.
• Holding your breath. "Holding your breath can create unnecessary tension in your neck and lower back and lead to poor intra-abdominal pressure", Lefkowith explains. "Exhale as you lift to keep your abs engaged".

There are many ways you can do crunches. Here are several options, based on fitness level and comfort.

1. Place your heels on a bench with your knees bent to about 90 degrees.
2. Press your lower back into the floor and place your hands behind your head.
3. Gently push down into the bench to reduce hip-flexor involvement and maintain a posterior pelvic tilt.
4. Curl your shoulder blades up using your abs, rolling up one vertebra at a time.

Why this variation works for beginners: elevating your heels on the bench allows you to push down and reduce your hip flexors' involvement in the move, Lefkowith says. "It also makes it easier to maintain a posterior pelvic tilt, so your abs do more of the work".

1. Lie on your back with the soles of your feet together and knees open wide.
2. Press your lower back towards the ground and place your hands behind your head with elbows open.
3. Engage your abs and glutes for stability in the externally rotated position.
4. Slowly roll up, lifting your shoulder blades by curling your ribs towards your pelvis.

Why this variation works for beginners: "Opening your knees out wide with your feet together relaxes your hip flexors and helps isolate true spinal flexion, so beginners can better feel their abs working", Lefkowith says. "This can also help you engage your glutes for stability, due to the external hip rotation".

1. Lie on your back and press your lower back into the floor.
2. Engage your abs and tuck one knee towards your chest.
3. Lower that leg, then repeat with the opposite knee, keeping your pelvis stable.
4. Focus on curling through your lower back rather than moving only at your hips.
5. To increase the challenge, lift your upper body into a slight crunch and hold while marching your legs.

Why this variation works for beginners: "By lifting one knee at a time, this crunch teaches beginners how to keep their pelvis steady and target their abs instead of their hip flexors", Lefkowith says. It's a useful stepping stone toward more advanced core moves, such as lower body crunches and leg raises.

1. Lie on your back with your hands behind your head and elbows wide.
2. Lift your shoulder blades off the floor and draw your knees into a tabletop position.
3. Extend your right leg out while simultaneously bringing your left knee in.
4. Rotate your torso to bring your right elbow towards your left knee.
5. Switch sides—extend your left leg and draw your right knee in as you rotate your torso to meet it with your left elbow.
6. Continue alternating sides in a smooth, controlled pedalling motion.

Why this variation works for those looking for a challenge: This movement requires a bit more coordination than the beginner-friendly variations above. "Bringing the elbow to the opposite knee activates the oblique muscles", Solomon explains, so you're also working those core muscles in addition to your rectus abdominis.

1. Place the BOSU ball under your mid-back while sitting and gently lean back until your spine arches over the dome.
2. Position your feet firmly on the floor and place your hands behind your head with your elbows wide.
3. Allow your torso to extend over the ball to create a longer range of motion.
4. Press your lower back into the BOSU to engage your abs.
5. Roll up one vertebra at a time, lifting your shoulder blades off the ball.
6. Pause briefly at the top, then slowly lower back into the extended position with control.

Why this variation works for those looking for a challenge: "Using a BOSU ball increases your range of motion by allowing more spinal extension before the crunch, creating a deeper contraction", says Lefkowith.

1. Lie on your back with your knees bent and hands behind your head.
2. Engage your abs and press your lower back gently towards the floor.
3. Exhale as you lift your shoulder blades off the ground and curl your knees towards your chest, rounding through your lower back.
4. Pause briefly at the top, keeping the focus on your abs rather than your hip flexors.
5. Extend your legs close to the floor as you lower your shoulder blades back down with control.
6. Repeat, maintaining the rounded spine as you draw your knees in to keep the work in your abs—not just at the hips.

Why this variation works for those looking for a challenge: "A full-body crunch incorporates lower body movement to challenge your abs through spinal flexion and boost overall core engagement", Lefkowith says.