Dynamic Effort (speed strength) is defined as lifting sub-maximal weights explosively. Repetition Method (strength endurance/lactic acid tolerance) is defined as lifting sub-maximal weights to concentric muscle failure. Is it possible to combine them, lifting sub-maximal weights explosively to concentric muscle failure, in the interest of efficiency?

No. The point of dynamic lifting is pure quality, every rep is highly explosive and of the highest quality. This is nervous system training. This means avoiding fatigue. The point of the repetition method to failure (or not) is the generation of fatigue. They are mutually exclusive and dynamic method to fatigue is a contradiction in terms. If one was trying to build speed/power endurance, tehy could use the dynmamic method for reps but the set would stop as soon as movement speed decreased. Lyle

So what would happen if you were to combine them? The first few reps would still be of high quality, so that would follow the guidelines of dynamic effort. The remaining reps would be there to induce fatigue, hence following the guidelines of repetition method. Am I missing something here?

As lyle said, they are mutually exclusive If you try and do DE to failure, it wont be DE... ooo that sounds gooooood it must be early am again...

What if I left some reps in the tank? I asked another knowledgable person on a different forum, and they said that combining dynamic effort & repetition method would build "power endurance."

You state yourself that the Repetiton method requires going to failure so how can you leave a few reps in the tank and go to failure at the same time? If you try and combine them in this way then you arent doing the repetition method anymore, thats why theyre mutually exclusive. Just accept that there arent any short cuts to get the results you want. Maybe he meant combining them in the same overall training routine, not the same workout? You could do them both on different days and get the results youre after.

The Repetition Method can also be done to near-failure (i.e. leaving a few reps in the tank). I'm not looking for shortcuts, rather for efficiency. He definitely meant combining them in the same exercise.