The Alternate Curling Machine is a machine specifically designed to isolate the pecs and biceps. What makes it unique is that its seat comes with gas-assisted height adjustment, allowing users to adjust the height of the machine to suit their needs. In addition, it is equipped with a rotating joint handle and adaptive system, as well as a balancing mechanism. These features provide users with a more comfortable and safer exercise experience. Alternating curl machine for developing biceps and some forearm muscles. Do the exercise - Sit at your desk and bend your arms to engage your biceps. Alternating Curl Machine Curl your biceps with a dumbbell on a music stand, causing your forearm to supinate (rotate around its longitudinal axis). The ability to supinate the forearm allows for better isolation of the targeted muscles.