The case against doing crunches:
No one needs to perform hundreds or even dozens of crunches, said Brad Schoenfeld, a professor of exercise science at Lehman College in the Bronx and an author of a newly published review article about core exercises titled “To Crunch or Not to Crunch.” And while everyone needs some basic minimum of core strength — getting up out of a chair requires a certain amount of core strength; serving a tennis ball requires more – “six or eight crunches would be plenty,” he said, “and only a few times a week.”
It’s also important you perform them correctly, Dr. McGill said. “Don’t flatten your back into the ground,” he said. Instead, place your hands, palm down, beneath your lower back to lessen pressure on the spine. Bend your knees, and “pretend that your head and shoulders are resting on a bathroom scale,” he said. Lift them only enough to send the imaginary scale’s reading to zero. “You don’t need to crunch up very much” to achieve the desired workload on the abdominal muscles, he said.
Or forgo the crunches altogether. “Personally, I do not believe that it is necessary to specifically train the core,” said Thomas Nesser, an associate professor of exercise science at Indiana State and senior author of the study about core stability and performance. In most instances, if you “train for your sport, core strength will develop,” he said, and it will be the right amount and type of core strength for that sport.