As you probably know, there are two kinds of training for the muscles in your core, direct and indirect. Direct training simply means that you are doing exercises that specifically target your abs. For example, in crunches you are flexing your trunk and as a result engaging the Rectus Abdominis. Indirect training includes compound movements that train the abs indirectly as well as many other muscle groups. Some of the most well-known compound movements that train the abs indirectly include the squat, deadlift, military press and even pull-ups.
So is indirect training enough for the abs?
By doing solely indirect training for your abs, you can still get results for sure. In almost all of the compound movements the abs stabilize our body. This is important because the abs protect our back from an injury and they exert an additional force that help to us to complete the movement. Thus, the muscle microfibers in the core tear and become thicker and stronger with each training that involve challenging compound moments (especially the transversus abdominis). Even thought compound movement are crucial when it comes to abs development, training your abs directly will result in a better development of more muscles fibers in your abs (which means a stronger , more athletic and aesthetic core:)).
For how long should I be including isolated abs work? What if I do not have the time?
I recommend you to train your abs directly (isolated movements) 2 -3 times a week at the end your main workouts. Some of the isolated movements you can do at the end of the workout include (but are not limited to) the plank, weighted crunches and Russian twists. Your abs training should generally last between 5 – 15 minutes but can vary between different individuals. If you really do not have the time to incorporate direct abs training into your workouts, you should prioritize compound movements as the bulk of your workout routine since they are the most effective exercises for building more muscle mass and strength. Regardless, make sure your nutrition is on point to see the results you desire.
In one word, the answer is definitely. Direct abs workouts offer a new stimulation to the muscle fibers, which in turn yield better results in terms of muscular development. Make those direct abs workout short and effective as much as you can. Also, always remember to prioritize compound movements in your workouts that activate many muscles fibers at the same time (including the abs). Though isolated work for the abs is a significant bonus, compound movements still should be your main focus.