There are plenty of guides about heavy lifting which suggest to hold the breath to help brace the core.
Here there is an example with squat. Picture taken from here.
Many people agree with this as it provides a great trunk stability. All the guides of stronglift suggest it.
However, I've seen plenty of other guides that say it is a big mistake. So, I've found only confusion.
For instance, here "holding the breath" is seen as a mistake in leg press:
Remember to keep breathing during the effort phase and to avoid holding your breath.
That is not the arbitrary conclusion of an author. Here, for instance, it is written that:
The act of holding your breath during weight lifting is referred to as the Valsalva Maneuver. While this may not sound like a serious issue, it can be. Holding your breath during weight training causes a rapid and dramatic increase in blood pressure. During the Valsalva Maneuver, intrabdominal pressure drastically increases and can lead to hernias. Other injuries can be caused by compromised areas of the vascular system and loss of consciousness. While it may be tempting to hold your breath during exercise, the most effective way to breathe during resistance training is to inhale as you lower the weight and exhale as you lift the weight. This helps to control your blood pressure while lifting heavy weights.
One may answer that a good choice may be:
1 holding breath in heavy exercises
2 inhaling in the eccentric and exhaling in the concentric without heavy loads
But what does it mean in practice? If I do 2 sets of warm-up I breath as 2, and when I start heavy sets do I breath as 1? Or is 1 only suitable to lift the maximal?