This gym-class standard needs
an update: According to research from San Diego State University, the
traditional crunch is the least effective strengthener for both the
rectus abdominus (6-pack muscles) and the obliques (waist muscles).
What's more, because sit-ups require more strength from front ab muscles
than obliques, this move can create a strength imbalance in the core --
setting you up for back problems.
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Not only does the plank
require more muscle activation in the obliques than the traditional
crunch, according to research, but researchers have also found that
practicing this position can actually help lower the risk of developing
lower back pain later in life, according to Matthews. Why? "The plank
targets your abdominal muscles, helps to build muscular endurance and
spares your spine in the process," she says.
