Myth: Training the core or the abdominals will help develop an attractive "6 pack" appearance. The research is very clear that training the abs, regardless of he choice of exercise, volume of exercise, or frequency of exercise, does not reduce body fat, reduce waist circumference or improve abdominal appearance. Period. Simply, the "rectus abdominis", the muscle under abdominal fat, becomes stronger in response to training, but the fat that covers this muscle remains unchanged.
Myth: Training the abs or core is important for athletic performance. Indeed, it is the most prevalent of myths. The "core" is where it all starts for an athlete. Well, the authors of a new study examined the role of "core" training on athletic performance and general fitness. The conclusion was that trunk muscle strength plays only a minor role for physical fitness and athletic performance in trained individuals.
Myth: You can selectively train your upper and lower abs. Based on EMG activity recorded during the performance of various abdominal exercises, it appears to be impossible to differentially recruit the "upper" or "lower" abdominal muscles. You may feel a particular abdominal exercise more or less in your upper or lower abs; but regardless of where you feel it, the entire abdominal sheath is receiving equal stimulation.