Don't put too much effort into abs.  While I do think some direct ab work is good, just a few sets of week is likely fine.  Any more than that is just a distraction from building muscle, which will have a much larger effect on your body composition (and in turn your six pack) than direct ab work.  Also if you aren't doing deadlifts, good mornings, or hyperextensions, make sure you balance out the ab work with direct work on the erector spinae.

It is likely that most people do not know how to do diaphragmatic breathing when lifting/specifically doing ab exercises. Not doing this/not doing it correctly takes away a lot of abdominal muscle development that you would see from doing other lifting aside from abs and requires you to do 5x the amount of ab work required. Learning to do this should be the base block of someone wanting to train their abdominals.

I disagree somewhat.  First, younger people generally don't have that much trouble with diaphragmatic breathing, unless they are a mouth breather.  If they aren't fully activating their diaphragm, they can learn how to do it relatively quickly.  Second, I really only think diaphragmatic breathing is important if you are using a lifting belt.  If you aren't using a belt, simply bracing yourself is better.  I do think diaphragmatic breathing is very important for general health though.

Don't put too much effort into abs.  While I do think some direct ab work is good, just a few sets of week is likely fine.  Any more than that is just a distraction from building muscle, which will have a much larger effect on your body composition (and in turn your six pack) than direct ab work.  Also if you aren't doing deadlifts, good mornings, or hyperextensions, make sure you balance out the ab work with direct work on the erector spinae.

It is likely that most people do not know how to do diaphragmatic breathing when lifting/specifically doing ab exercises. Not doing this/not doing it correctly takes away a lot of abdominal muscle development that you would see from doing other lifting aside from abs and requires you to do 5x the amount of ab work required. Learning to do this should be the base block of someone wanting to train their abdominals.

I disagree somewhat.  First, younger people generally don't have that much trouble with diaphragmatic breathing, unless they are a mouth breather.  If they aren't fully activating their diaphragm, they can learn how to do it relatively quickly.  Second, I really only think diaphragmatic breathing is important if you are using a lifting belt.  If you aren't using a belt, simply bracing yourself is better.  I do think diaphragmatic breathing is very important for general health though.

Even if you aren't wearing a belt, you still want to take a diaphragmatic breath in order to brace. The whole idea of bracing is to pressurize the musculature around your lumbar spine, mostly, and you won't get the best pressure in there if you're breathing "into your chest."Edit: I think what cgrims was referring to is the ability to breathe and maintain IAP under load.. It's really easy to teach someone to use their diaphragm and brace, but it's very hard to learn how to maintain that when you begin to breathe hard while doing squats for 8 reps or something.

Every breathe should be a diaphragmatic breathe.  My point is diaphragmatic breathing isn't holding back many people back.  It's something that doesn't really need to be worried about with respect to training until you are pretty advanced.I do think diaphragmatic breathing is very important for health because it's a basic human function that should be automatic.  However, with respect to training, it's not reason most people don't have the abdominal development or strength they want.  They just need to lift heavy and do a couple sets of direct ab work.