This is the first in a multi-post series that will address common core exercises that might actually do more harm than good.
The Move: crunch combined with reverse crunch, and a double leg lift.
The Verdict: Unsafe
What is wrong with it:
When lifting the shoulder blades off the floor from a supine (back-lying) position, the abdominal muscles automatically bulge forward, as visible in the above photo. This is not dependent on individual strength, ability, or any attempts to engage the core, but rather a fact of biomechanics. The moment your abdominal wall bulges forward, that forward pressure exerts stress on the linea alba, the connective tissue that lies vertically along your midline.
- Reverse crunches
Similarly, the lower abs bulge forward under acute pressure with each lift of the hips when performing reverse crunches. Each of these moves is independently injurious to the core, and when combined intra-abdominal pressure increases even more dramatically. When the abdominal muscles bulge forward, the pelvic floor echoes that in a similar external bulge, stressing and weakening the pelvic floor muscles. No matter how strong you are, crunches and reverse crunches compromise core health.
- Double leg lift
Very few people, athletes and fitness instructors included, have the core strength to safely lift both legs off the floor from a back-lying position without bulging the abs and arching the back. If you cannot lift both straight legs off the floor with your belly button absolutely fastened to the spine, while exhaling and drawing your abs even flatter to the spine, you should not lift both legs off the floor at the same time while lying on your back. This will cause or worsen abdominal separation and compromise spinal health.
Repeated, forceful mechanical stress on the connective tissue weakens and overstretches it, causing the two halves of the rectus abdominis to migrate further apart from each other. This not only widens the waistline, but it also compromises core strength and function. When we lose integrity and strength front and center as occurs with abdominal separation (also called diastasis recti), we are more likely to experience back pain, urinary stress incontinence (leaking when you run or jump), and pelvic prolapse. While the goal of this combo move is decent – to engage and strengthen the upper abs and lower abs simultaneously, it inflicts collateral damage by straining the connective tissue throughout the entire length of the abdomen and also exerts stress on the pelvic floor.
What to do instead: Waist cinchers combined with single leg lifts*
There is a better way to safely and efficiently engage the entire length of the rectus abdominis, along with proper recruitment of the deep core muscles (transverse abdominis, diaphragm, lumbar multifidus, and pelvic floor). To do so, I recommend performing waist cinchers with single leg lifts as an alternative to crunches and double leg lifts.
Begin by lying on your back with your knees bent (remember to get down safely!). Then extend one leg with foot flexed. Place one hand on your abs, directly over the belly button. Tuck the other hand under your head to support the neck. Prepare by taking a small breath. Then exhale and draw your belly button flat to the spine as you nod your head “yes” and lift the extended leg several inches off the floor. Be sure to draw the chin gently toward the chest as you nod – it’s a tiny movement. The shoulder blades stay in contact with the mat throughout the entire range of motion. Inhale as you return your head to the starting position, lower the leg and soften the abs.
With each pulsing repetition, flatten your abs toward the spine as you exhale and nod “yes.” If the head nod bothers your neck, leave your head down and focus on flattening your belly into the floor with each leg lift. Perform 10 slow, controlled repetitions. Then switch your legs and perform a second set. Complete this cycle 2-3 times.
For video instruction and guided coaching in this and many other exercises, check out our library of EMbody workouts.
*This exercise is not recommended during pregnancy.