One palm forward, one back, for grip variety and big pulls.
Keep your chest from rotating toward the underhand side, stay square the whole pull.
Running one palm toward you and one away splits the pull down the middle, the underhand side gives its biceps more leverage while the overhand side pulls more lat-dominant, and your trunk has to resist the twist that asymmetry creates. Keeping the chest square under an uneven grip is real anti-rotation work layered onto a vertical pull. Alternating which hand faces which way between sets keeps the stimulus balanced while giving your grip and elbows a change from endless standard pull-ups.
Not if you swap the grip every set so both sides spend equal time underhand and overhand. The asymmetry is the training stimulus, the swap is what keeps it fair.
The underhand side has better pulling leverage, so it wins unless your core intervenes. Brace before you pull and drive both elbows down together, if you still corkscrew, do fewer reps with stricter symmetry.
The pull itself sits between a pull-up and a chin-up in difficulty, but the anti-rotation demand adds work regular grips never ask for. Most people find them a refreshing middle ground rather than a step up.
