Delt "sweeps" work well for high reps in metabolic stress fashion:
The execution is really important. On the lifting side, it's really a pull back – as if you were doing a face pull and lateral raise hybrid. With the supporting arm you're going to be pushing slightly as you lift with the other arm. (It's not a one-arm upright row motion.)
If you get this right you'll feel it big time in the lateral delt and even some posterior delt and traps. Start light and play around with it until you can feel the contraction.
Most trainees have the habit of waking up, shoveling down some Fruit Loops, and heading off to the gym before they've truly awakened. In other words, given the amount of prep work they've put into that particular workout, they might as well have left their Fozzie Bear jammies on and stayed in bed.