The rotary torso machine locks your lower body into the seat and turns your upper body against a weight stack, one direction at a time. It is the simplest way to put a measurable load on rotation — the same job as a cable woodchop, minus the balance and the setup, with a number you can add to in steps.
How to do it
- Set the start angle, sit tall and lock your legs in the pads.
- Turn from the ribs, slowly, and stop where the hips would have to follow.
- Let the stack back under control, and finish all reps one way before switching.
Common mistakes
- Loading it heavy and yanking the turn with the arms and momentum.
- Letting the weight snap back at the end of each rep.
What it trains
- Obliques
- turn the ribcage against the stack — the prime mover
- Abs
- keep the trunk braced and upright so the movement is a turn, not a lean
- Lower back
- hold you tall on the seat through the whole turn
Variations and alternatives
Common questions
Do I log both sides?
No — use the same weight both ways and log the reps of one side. Twelve each way goes in as 12, and StackUp judges your heaviest working set against your rep range and suggests the next weight from that.
Is the rotary torso the same as the ab machine?
It is one of two machines people call that. This one turns you side to side and trains the obliques; the one where you curl forward against a pad is the machine crunch. StackUp keeps them as separate exercises, because a weight on one says nothing about the other.
How far should I rotate?
Only as far as you can turn without your hips shifting on the seat — for most people well short of the machine's end stop. Set the start angle so you begin in a slight stretch, turn under control and pause briefly at the end instead of bouncing off it.
How much weight should I use on the rotary torso machine?
Less than on most machines: a weight you can turn slowly for 10 to 15 reps each way with a pause at the end. The stack often jumps in bigger steps than the 2.5 kg StackUp uses by default, so set this exercise's step to what your machine actually allows.
In StackUp. Logged as weight and reps per set, and your heaviest working set decides whether the weight goes up next time. Get the app.
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