IAP is probably more important for heavy weight-lifters with big loads rather than body weight squats and day to day loads.

There is absolutely no need to hold your breath to have an affect on IAP with BODYWEIGHT exercises in the vast majority of people, even in those who have a history of low back pain.

I have seen many patients who are completely obssessed with holding their breath for every day activities because this sort of advice has been dished out to the public and many become fearful and avoid doing any basic body weight squat or hinge function (eg: picking something off the floor) without first taking a breath in and holding it, that is unhealthy and may actually cause more issues than it's helping. We have to spend months and sometimes years retraining these people that it's ok to breath normally whilst moving as this concept of "core" and "breath holding" has been taken way out of context and applied to the wrong pouplations.

This concept is often also confused with "turning on your core" and it was based on research by Peter O'Sullivan an others 20+ years ago which he has since retracted. You can see some good information about this here: https://bjsm.bmj.com/content/54/12/698

Again, 99% of people do not need to hold their breath when doing bodyweigth squatting or bending over unless they are doing very high loads in the gym or in life and it is probably better for these people to focus on their technique first if they repetitive lift heavy loads before focusing on holding their breath.

Everyone is completely different, noone should ever tell the word "this worked for me so this is how you shoudl so it", and the public should be encouraged to seek advice from the relevant experienced professionals, more on why here: https://physioclinician.medium.com/why-i-dont-post-exercise-demonstrations-on-social-media-d9f955de5152.