With mechanical drop sets, instead of dropping down to lighter weights when you reach failure, you keep the same weights but switch to a related exercise where you have a mechanical advantage. This allows you extend the set, triggering metabolic stress and increasing time under tension, both crucial for hypertrophy.

Here's an example for arms:

1. Start with 8-10 Zottman curls. Curl the weight up normally and then rotate your wrist into a palms-down position to lower the weight.
2. Now do 8-10 hammer curls without resting.
3. Finally, rep out with 8-10 alternating dumbbell curls.