I've been working out 4-6 times per week for the last 14 months, mostly with the Firm and recently (just 3 weeks) with Cathe. I've been able to increase my weights on several exercises, both lower and upper body, EXCEPT for biceps. I cannot seem to lift heavier than 8 pound dumbells, and even that is too heavy sometimes. I've tried to use 10 pounds for a couple of reps but always have to go back to 8 because I get a pain (not a burning) in the bicep. Is it possible that some muscles in some people just don't get stronger? I have been using PUB at least 1 time per week (for the last 3) and have just recently purchased the remaining Intensity series, preordered the Body Blast Series, and have Slow & Heavy on the way. Any thoughts or recommendations? Thanks in advance!