Dancers must have strong core muscles (abdominal and back) to have good posture and a strong center to support movement. A common exercise used is crunches, but they are not the only way to gain strength! Using crunches for gaining abdominal strength is valuable to a point, but research shows that over using spinal flexion (rounding forward), can lead to herniated discs. So what other exercise can we use for abdominal strengthening?
One good alternative is the "side plank." One study in which researchers examined six common ab exercises performed by 120 subjects to see how hard the muscles were working showed some interesting results. When compared to other common ab exercises, the side plank and the classic abdominal crunch both resulted in the greatest change in muscle thickness for the transverse abdominis and internal oblique muscles (meaning they were contracting the muscles more than the other exercises). The reason the side plank is a good choice is because it does not involve spinal flexion, and because it builds abdominal endurance (previously found to be associated with less low-back pain). The side plank also aids your total-body fat-burning workout.
To do the side plank, lie on your right side. Bend your right arm at the elbow and stack your left foot on top of your right foot. Supporting your body weight on your right forearm and your right foot, raise your body in a straight line. Your butt and thighs should hover a few inches above your mat. Keep your back straight and your hips up. Hold your abs tight, but breathe normally. Beginners should hold this position for 15 seconds on each side. Try to hold it a little longer with each workout. For advanced core strength, hold for 45 seconds per side.