Most lifters have used the classic 21 method with biceps curls. Reverse 21's invert the usual order. Start with the hardest part of the set and finish with the easiest part.
- Start with 7 full reps.
- Do 7 top-half partials.
- Finish with 7 bottom-half partials.
Reverse 21's function as a mechanical drop-set whereby the set gets easier as fatigue sets in. This method works really well for chin-ups and can easily be modified to fit your current ability level.
Reverse 21 Chin-Ups
Start with full reps, then do top-half partials where you start with your upper arms parallel to the floor and pull yourself all the way up. Finish with bottom-range partials where you start with your arms fully extended and pull up until your upper arms are approximately parallel to the floor.
Feel free to use a bar or rings. If 21 total reps is too ambitious at first, adjust accordingly. Even if you're doing 2-3 reps per mini-set, you'll get results. Lat pulldowns also work well with this method.