Wondering if any of the advanced age lifters here (I'm in my late 30's) ever have a problem with this.
Recently I started lifting heavier again wanting to gain some strength back which has been going very well. However, just recently I've noticed that after about 8-10 sets my system starts to go a little haywire - shaky, feeling lightheaded sometimes and very tired afterwards with poor concentration. I'm doing about a 5-8RM program depending on the muscle group.
Could I just be using too short rest between sets? I normally rest for anywhere from 45-90 seconds.