Hmm I have a question that you might be able to shed some light on for me. How do your muscles feel the days following your workouts? I guess I assume that I should at least be a little sore after a good workout but lately I haven't been at all. I raised my weights 2 weeks ago and fatigue at about 10 or so reps so I don't believe its because of the amount of weight I am using. And for reference I alternate between bi's and tri's.. 2-3 exercises for each, 4 sets and I go till my arms cant lift for another rep.
Because your body has adapted to your regular exercise routine it is no longer sore, this doesn't mean that your routine has stopped being effective though.
At the start of a new program i will feel sore because i am hitting the muscles in a slightly different way to how i was previously and i will be sore after i have had a break from training but after a week or so I will have very little in the way of DOMS
Also as far as strenght training goes, the speed and number of reps can make a big difference to what you are trying to achieve.
Low reps, slow/moderate speed, high weight for strength
Low reps, high sets, high speed, moderate weight for power
Moderate reps, sets and weight at a V slow/medium speed for mass
high reps, low weight, low sets medium speed for endurance
the dynamic lifts in my program at the moment are to develop explosive power and to force the muscles to only use the ATP-PC energy system during the lifts as the sets are not long enough to make use of the lactate system or to be aerobic in nature