Sit on a sturdy object (any chair, bench, or large rock will do), your feet planted on the ground slightly wider than shoulder-width apart. Lean forward and place your right elbow against the inside of your right thigh, just above your knee, allowing your forearm to hang straight down. Press your elbow into your thigh throughout the exercise, fixing your arm in place.
Bend your right elbow slightly, bringing your right palm upward so you can clasp your right hand with your left. Your left hand and arm are responsible for providing resistance during the curl.
Tighten your right biceps and begin bending your elbow to draw your right palm to your right shoulder, but as you do so, press downward through your left hand to resist the curl, making it harder. When your right hand reaches your right shoulder, reverse the movement, continuing to press down through your left palm as you use your right biceps to control the downward phase. Perform this exercise slowly to maximize resistance in both directions. Perform 10 to 15 repetitions before switching sides.