Biceps curl with a cable machine lying on a flat bench

Flex the elbow without letting the shoulder drift forward or the torso swing. Lower the load under control until the starting position is restored. Use a steady tempo: control the return phase in particular and avoid relying on momentum. Exhale through the hardest part and inhale as you recover the starting position.

Check that the movement stays stable in both directions and that the torso is not compensating. The goal is controlled loading of biceps; match resistance and range to a intermediate level and never force a painful repetition. Keep resistance continuous and avoid letting the cable or band suddenly go slack.