Straight Bar Cable Curl

The straight bar cable curl trains the biceps against a low pulley rather than a free weight, and the difference lives at the bottom of the repetition. With a barbell, the resistance at the fully extended position is close to zero because the weight hangs in line with the arm; the cable pulls along its own line, so the biceps is loaded from the first degree of flexion. That matters because the stretched position is where a good part of the growth stimulus comes from. The straight bar keeps both hands supinated at a fixed distance, which is the strongest grip position and lets you load the movement more heavily than a rope would. Keep the elbows pinned to your sides, and watch for leaning back as the set gets hard, which turns the curl into a partial row.