Use a pulldown machine that allows you to work unilaterally (one arm at a time) like the Hammer Strength isolateral machine. Add a band to increase tension in the contracted position.
Increase time under tension by keeping one arm fully contracted while the other arm cranks out reps. Here's how to do a 5-4-3 rep scheme this way:
- Bring both arms into the contracted position, then while holding one arm there and keeping it contracted, do five reps on the other side.
- Alternate sides so that when one arm is done with the reps, the other side begins.
- Go from five reps on each side, then four, then three.
So while each arm gets a total of twelve reps, the "resting arm" never really rests.