This article is simply wonderful. Grimek is the man to listen to concerning this topic of chest expansion. I firmly believe in this type of training and do my best to implement it in every program. I include Rader Pulls generally between sets as these seem to work as well as many varieties of pullovers and some of Grimek's exercises. The key is to force deep breathing - like when you finish a set of high rep leg work and the body needs to keep breathing for up to a couple minutes afterward. One can actually get quite good at "forcing" recovery with the conjunctive use of pullover type exercises.
One of the greatest training benefits I have found from including these exercises is rapid recovery. I mainly think this is due to super oxygenation of bodily tissues. Light high rep leg training as he recommends will eventually cause failure not in muscle specific strength, but nervous function by the actions of oxygen debt. I also find my fatigue is much less after a session - if it was a light session I actually feel more energetic after leaving the gym. If it was heavy I am almost always ready to go for another session within 48 hours.
I have noticed that my body actually begins to crave deep forced breathing and, like Grimek explains, the benefits go beyond a larger bust and bigger rib box. I'll admit that at first these are actually quite painful but in time (a couple months) I generally feel awesome from these, maybe it helps endorphin release, but I actually begin to crave this type of work.
Some other things I have noticed are increased metabolism and a leaner harder physique in time with these. If I do them once a week I actually notice my metabolism slow within 3-4 days after doing them - no other training brings my metabolism back to that high rate.
I really think these are the best exercise for gaining lean hard weight as naturally and as quickly as possible when one performs many sets over 2-3 sessions a week in a progressive fashion. They can also be used maintain without the inclusion of progression.
It has come to a point in my training career after personally witnessing the benefits of these that all other training that I do seems pointless. If I ain't doing these - why bother?
The breathing squat is the most legendary exercise of them all...from it, all champions are born.