Strength and Physique

In  High Tension Exercises for Muscular Growth  I discuss how high muscular tension is the primary factor for muscular hypertrophy.  The tension has to be high enough, but also long enough.  The optimal time under tension to build muscle is 40-60 seconds.  In other words, the set has to last that long in order for you to grow. The problem is that when people lift, they stick to the traditional range of 6-10 reps.  Their sets last no longer  than 20-30 seconds. Timed sets allow you to focus on accomplishing the goal (optimal time under tension) as opposed to the accomplishing the task (hitting a target rep).

I have a training question. Over time, I have read a number of training routines of bodybuilders and weightlifters. I am familiar with the pyramid technique in which the weight goes up but the reps go down; for instance on a dumbbell curl:   25lbs x 12 30lbs x 9 35lbs x 7 40lbs x 4 and so forth.   What caught my attention is many of these bodybuilders/ weightlifters I've read about would go up in weight over the course of four or five sets, but the reps would be the same:   25lbs x 12 30lbs x 12 35 lbs x12 40lbs x12 45lbs x 12.   It seems to me that sets 1 through 4 are submaximal.  Other wise the reps would go down... but what is the benefit? Are they all warm ups? Why would weightlifters or bodybuilders put effort into only their last set? I know going to failure on every set can be counter productive but this seems like "under training" to me. Am I missing something?   Thank you very much for your time! ...