It is never a good idea to go dive head first into ab workouts if your core is not warmed up yet. Clearly, if you plan on working out this region after your original workout regimen then your body is already warmed up and you will be good to go. However, if you want to start with some abdominal exercises then warm up beforehand. This can be as simple as performing some stretching activities or even some light shoulder rotations. Just get your body ready to go.