QUAD- I'm 42 and I have run this exact program very successfully multiple times and plan to continue to "keep it in the rotation" . My shoulders handled this with no problems ,and quite frankly I can't imagine the shoulder issues I would have if I DIDN'T OHP regularly! SAYWORD- This is very much a strength program and is suitable for ALMOST anyone with those goals. I feel it would be irresponsible not to add that a beginner should not be messing about at such high intensity as this is not the arena to be learning form or sorting out form issues, as injury and connective tissue strain is pretty much guaranteed if one was to haphazardly start "throwing around" 90% of their 1RM! Programs based around 70% 1RM are safer, more appropriate territory for beginners to hone their chops in. You need to have a solid handle on form/technique for all lifts before embarking on this but if that's "tight" go for it - it will either suit your temperament (be something you can get excited about ) as a lifter or it won't and you won't know till you've given it a shot. I've noticed that some lifters enjoy slightly less intense mental focus over longer set times and some thrive on short but incredibly focused set times- (oddly enough I've also never met a lifter who won't CLAIM 100% mental focus...pride or self delusion?) - put another way an out and out bodybuilder may spend very little of his workout NOT working out contrasted to a strength lifter spending most of his workout in between sets! Temperament is a huge factor in finding whats right for you but is largely (as the mental component of lifting is in general) unaddressed or ignored. As for breaks - as long as you need. IMHO "timed" breaks between sets are for hypertrophy oriented programs . In strength training , "rushing" will be counter productive and limiting. Needless to say (hopefully) sleep/rest , nutrition etc. has to be in order. The cool thing is the built in "deload" and progression , by dropping back down to 4 sets , although the load is (slightly) higher the volume has just dropped substantially readying the bodies systems for the next gradual progression in volume- Hepburn was brilliant .