90 seconds with a medium size band you are able to perform full reps under constant tension, constant motion. No resting, even for a split second!
3 x 10 reps, one band larger than you used in round 1. It should be difficult to get to the tenth rep. If you end up at 8-9 reps, don't worry. Do your best! Take a short break of around 20-30 seconds between each set of 10. Go through three sets of ten reps with consistent effort.
90 seconds with a small band under constant tension, constant motion. This should be one band smaller than the band you used for round 1. Perform reps at a faster tempo than you did in round 1, but keep your form tight.