Single Arm Cable Curl

The single arm cable curl trains the biceps against a cable rather than a free weight, and the difference shows at both ends of the repetition. A dumbbell offers almost no resistance at the very bottom and again at the very top, because the load acts straight down; a cable pulls along its own line, so tension stays on the muscle through the entire range. Working one arm at a time lets you watch the elbow, which is where curls usually go wrong, and lets you correct strength differences between sides that a barbell quietly averages out. Stand facing the machine with the working arm hanging straight down and keep the upper arm still throughout. If the elbow drifts forward as you curl, the shoulder has joined in and the biceps has been given an easier job than the one you intended.