Originally Posted by Jason R O'Dell
Doesn't starting strength recommend taking a deep breath and holding it during many of the lifts?
This isn't necessarily dangerous unless the subject in question has a high blood pressure since the valsalva maneuver can cause a temporary spike in systolic blood pressure of well over 400 mmHg.
However, fainting can also occur in healthy individuals.
I generally practice inhaling deeply during the eccentric half of a lift and exhaling as I perform the concentric half. It's also not a bad idea to take several deep breaths in between extremely heavy repetitions.