Any time you go unilateral on an exercise – using only one arm or one leg – you're challenging your ability to control rotation via your core musculature. The angle of pull from the low cable provides constant tension on the biceps while the bilateral stance with unilateral pull challenges your ability to fight rotation.

If you can't use a heavy enough weight to fully challenge your biceps because the weight is twisting you around, work from a split-stance position first – one leg forward, one back.

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