The lean-away chin-up is a great exercise not only for your lats and biceps but also for the subscapularis, serratus anterior, triceps—and believe it or not, the abdominals.
Yes, a strong contribution from the abdominals is required to stabilize the core during lean-away chin-ups, especially when additional loading is used. It’s not uncommon to hear people complain of abdominal soreness for a day or two after doing this exercise!
Here’s how to do them…

Start from a dead hang. Your chin should clear the bar at the top of the movement. Lean back as you come down by pushing the bar away, and make sure to go all the way down at the bottom by fully extending your arms. Add weight to a chin/dip belt for additional loading.
Insert lean-away chin-ups in your next routine and use the protocol I laid out on page 31 of my book The Elite Trainer. Play your cards right, and you may end up sporting a set of six-pack abs this summer.

The Elite Trainer: Strength Training for the Serious Professional
The Elite Trainer is a synthesis of the very latest thinking in strength training and a comprehensive guide to developing individualized programs for your clients.
Intensity, volume, density, repetitions, sets, tempo, time under tension, rest interval, exercise selection and sequence, load selection, duration, and frequency are all covered in detail in easy-to-understand language. Whether you are a seasoned professional or a beginner, The Elite Trainer provides a wealth of information you can put to use immediately.