Given their bad rep, it's no surprised crunches have been pushed aside in favor of supposedly more effective abdominal exercises, such as the plank and Paloff press. Although crunches might be contraindicated for people with degenerative disc disease, osteoporosis or low back pain, for the vast majority of people, crunches are safe and effective at training the muscles at the front of your abdomen.
In fact, crunches are superior to full sit-ups and can build endurance in the abdominal region. The crunch doesn't provide a complete core workout, but no move does. While crunches aren't the only ab exercise you should do, it is beneficial to incorporate them in a workout or two per week that also includes training for your back, pelvis, obliques and transverse abdominis.
Better Than Full Sit-Ups
The crunch strengthens the rectus abdominis by flexing it. You'd think the sit-up would provide the same benefit, but more so because you go higher. However, as pointed out by exercise scientist Len Kravitz of the University of New Mexico, this primary ab muscle only activates during the first 30 to 45 degrees of movement — or the point at which your shoulder blades lift off of the ground.
Lift higher and your hip flexors activate, which can put excess stress on the lumbar spine. Your hip flexors tend to be overworked, so they don't need this additional exercise. The crunch's small range of motion is a benefit as it trains your core without stressing your back.
Your abs' primary role is to stabilize your mid-section. It helps maintain good posture, supports you as you lift heavy objects and makes it so you can twist and rotate. These are actions taken all day long, so it's important for your abs to be able to sustain long periods of work.
Crunches help build this important endurance in the muscles of the abdomen. Muscular endurance is the ability of these fibers to work against resistance for an extended period of time. Even just one day per week of crunches improved abdominal endurance in people who had no previous training in abdominal exercises, showed a 2015 study published in the Journal of Sports Medicine and Physical Fitness.
More Effective Than Gadgets
Infomercials promise you that your abs will become flat and defined if only you use their gadget. Unfortunately, most of these promises are too good to be true. In 2014, the American Council of Exercise performed a small study that pitted many of these tools — including the ab circle pro, ab roller, ab lounge and ab rocket — against the standard crunch to measure effectiveness.
Not one of the tools proved better at activating the muscles of the abdomen. Plus, you aren't out any cash or storage space with a crunch. You can do the move just about anywhere you have a little floor space and motivation.
Proper Crunch Form
Of course, the crunch provides no benefit and possible harm if you do the move improperly. Move through each repetition slowly and with intention to get the best results. Concentrate on the abs anatomical function as a connector of the ribs and pelvis, so you draw these areas together as you crunch.
Lie on your back with your knees bent. Plant your feet solidly in the floor a comfortable distance from your buttocks.
Let your hands cradle your head. Keep the elbows away from the ears.
Exhale and draw your belly button in toward your spine. Visualize them compressing together to help the lower back press into the floor. Simultaneously lift your head, neck and shoulders off the mat. No need to lift higher.
Pause momentarily and then inhale as you lower your upper body back down to the mat. Keep your feet, low back and tailbone in contact with the mat as you roll up and down.
To increase the challenge and muscle activation, perform the crunches off of a stability ball. However, master the basic crunch first.