Many people work their abs with the goal of a stronger midsection, but some of the most common exercises can place unnecessary stress on the spine and neck. Choosing safer alternatives and paying attention to form helps you build core stability without risking injury. This guide walks through five frequent ab workout mistakes, explains why they can be problematic, and shows you how to fix them with moves that protect your back while still challenging your core.
Five Common Core Training Mistakes and Safer Alternatives
ACE fitness experts have identified several traditional core exercises that carry a high risk-to-benefit ratio. The following swaps are based on that guidance, with steps described exactly as ACE presents them.
1. Sit-ups: High Spine Load, Low Deep Core Activation
According to ACE, sit-ups can place large amounts of stress on the lower spine and neck and do not target the deep abdominal muscles such as the transverse abdominis. A study cited by ACE found that bent- and straight-leg sit-ups placed more than 674 pounds of strain on the lower spine, which can lead to herniated discs and nerve damage. Instead, ACE recommends the McGill curl-up, one of the “Big Three” exercises identified by spine biomechanics researcher Dr. Stuart McGill. This move focuses on core strength and stability while putting minimal load on the spine.
To perform the McGill curl-up, lie flat on your back with only one knee bent. Place your hands under the small of your back to monitor movement, ensuring your back does not touch the floor. Brace your core muscles as if you were about to be punched in the stomach and lift the head and tops of the shoulders, keeping the spine in neutral. For an added challenge, lift the elbows off the floor. ACE suggests six to 10 holds, each lasting 10 seconds.
2. Back Extension Machine: Locked Hips, Lumbar Stress
ACE notes that the back extension machine locks the hips into place, so all of the stress is placed on the lumbar spine, which is not designed to handle heavy loads. This stress is amplified when weight is added. A safer alternative is the bird dog, a co-contraction of one leg and the opposite arm in the quadruped position.
Begin on hands and knees with your hands directly underneath your shoulders and knees directly underneath your hips. Find a neutral spine and gently brace the core. Sweep the floor with one hand and the opposite knee after each 10-second hold. ACE recommends repeating four to six times on each side.
3. Side Bends: Disc Herniation Risk
ACE explains that the discs of the spine serve as cushioning between each vertebral segment. If too much pressure is put on one side during a side bend, the soft center of the disc can be pushed out, increasing the risk of herniation. The side bridge, another of McGill’s “Big Three,” strengthens the side musculature without that uneven load.
Line your elbow up with your shoulder, and your shoulder up with your hip and heel. With a very tight and braced core, push the ground away from you, staying active in the shoulder joint. Hold for 10 seconds and repeat four to six times. To reduce the intensity, perform this exercise from the knees instead of the feet.
4. Partner Leg Slams: Excessive Spine Extension
ACE recalls that partner leg slams, where a partner throws your feet down toward the floor, can cause excessive extension of the spine and can be harmful for the lower back. A much better option, according to ACE, is the TRX resisted straight-leg raise.
Lay on the ground facing the anchor point; place both hands in the foot cradles and press down. While keeping your core braced, slowly lower one or both legs toward the ground until just before the low back raises up. Return to the starting position while keeping pressure down in the hands. Perform two 30-second sets of this exercise.
5. Plank Challenges: Long Holds Lose Value
ACE advises against holding a plank for several minutes. Planks held for an extended period lose their value and result in poor posture. For maximum strength and endurance gains, ACE suggests holding tighter, more active planks for a shorter period of time.
With your forearms on the ground and elbows directly under the shoulders, brace every muscle of your body, especially the glutes, and hold a perfectly straight line for 10 seconds on, two seconds off, for four to six sets. If you cannot complete a 10-second plank without the hips sagging, move your knees to the ground. For more on building stability, see our guide to core stability.
Form Cautions for Popular Ab Exercises
Even when you choose a generally safe exercise, small form errors can turn it into a back stressor. The ACE exercise library highlights specific pitfalls for the crunch, reverse crunch, and glute bridge.
Crunch: Avoid Momentum and Hip Flexor Dominance
ACE’s crunch instructions emphasize that individuals usually perform this movement too rapidly and recruit the hip flexors to assist with the upward phase. This technique tilts the pelvis anteriorly, increasing the stress on the low back and should be avoided. The abdominals connect the rib cage to the pelvis, so the movement should focus on bringing these two body parts closer together while keeping the neck and shoulders relaxed. During the upward phase, exhale, contract your abdominal and core muscles, and flex your chin slightly toward your chest while slowly curling your torso toward your thighs. Your feet, tailbone, and lower back should remain in contact with the mat at all times. For more form pointers, visit exercise form.
Reverse Crunch: Control the Legs, Protect the Low Back
According to ACE, proper form is important when performing the reverse crunch to prevent excessive stresses on your low back. When returning to your starting position during the repetitions, control your leg movement ensuring that your knees don’t move past your hips, but instead return to a position directly above your hips. Since the abdominals connect the rib cage to the pelvis, the emphasis of the movement should be on pulling your pelvis upwards toward your rib cage. Avoid any change in the angle of your knees during the roll-up.
Glute Bridge: Don’t Hyperextend the Low Back
ACE cautions that avoiding arching your lower back as you press your hips upward is key, which normally occurs if you attempt to push your hips as high as possible. This can be achieved by contracting your abdominal muscles prior to lifting, and keeping them engaged throughout the lift. During the upward phase, gently exhale while holding your abdominal contraction and press your hips upwards off the floor by contracting your glutes. Avoid pushing your hips too high, as this generally increases the amount of hyperextension in your low back. If you need modifications that are gentler on the back, check back-friendly modifications.
Avoiding Momentum in Core Circuits
ACE’s summer-inspired core circuit includes a hanging pike or V raise, where the goal is to keep the torso from swinging and to avoid using momentum. The circuit structure itself reinforces controlled movement: set a timer for 30 seconds for each exercise, with 10 to 15 seconds to transition between exercises. Complete all the exercises in order and then rest for 60 to 90 seconds before running through the circuit two to three more times. If your form starts to suffer, your body is probably becoming fatigued. When this happens, reduce your weight or modify your workout to help avoid injury. This approach applies to any core routine: slow, deliberate reps build strength safely.
Quick Checklist for Safer Core Training
- Swap high-load moves like sit-ups and side bends for spine-sparing alternatives such as the McGill curl-up, bird dog, and side bridge.
- Keep movements slow and controlled; never use momentum to complete a rep.
- Maintain a neutral spine and brace your core before each repetition.
- Stop immediately if you feel pain, especially in the low back, and consult a healthcare professional if you have a history of back issues.
- Remember that abdominal exercises alone do not reduce belly fat. ACE notes that a healthy diet and plenty of sleep are both essential to creating a better body.
For a deeper look at safe technique across all core exercises, read our pillar article on core exercise technique and safety. You can also explore the full technique and safety section for more guidance.
Frequently asked questions
Why are sit-ups considered a mistake for core training?
ACE explains that sit-ups place large amounts of stress on the lower spine and neck and do not target the deep abdominal muscles. Research cited by ACE found that sit-ups can put more than 674 pounds of strain on the lower spine, increasing the risk of disc herniation and nerve damage.
Can I still do crunches if I have back pain?
If you have back pain, an injury, or a health condition, check with a doctor or physical therapist before doing crunches. ACE notes that crunches performed too rapidly can tilt the pelvis and stress the low back. Stop any exercise that causes pain.
How long should I hold a plank?
ACE recommends holding a plank for 10 seconds at a time with a two-second rest, repeated for four to six sets, rather than holding for minutes. Short, active planks maintain good posture and build strength more effectively than long holds.
For more common mistakes and how to correct them, visit our Common Mistakes category page.
