Why do ab workouts hurt more than anything?
I do not know if you're referring to pain during or post ab training. But, I'll try and explain it. Ab muscles like any other muscle respond to contraction and extension. While your abs or more specifically your core is working all the time when you lift weights; isolating a muscle group will always lead to some amount of discomfort as you increase the number of repetitions. What happens to your biceps muscles on the 12th or 20th rep ? Pretty sure its tough to squeeze out those last 2–3 reps. Its same with your abs.
If you're referring to post training pain then its completely normal. The phenomenon is called DOMS ( Delayed Onset of Muscle Soreness). You'll feel particularly sore when you haven't worked your ab muscles in a while. NO PAIN NO GAIN. Right ? Always get enough protein. The pain will settle down. Just ride it out.
Peace out. WHEYmen !!