Biceps curl with dumbbells supported on a stability ball

Flex the elbow without letting the shoulder drift forward or the torso swing. Lower the load under control until the starting position is restored. Keep the same range from repetition to repetition instead of speeding up as you fatigue. Breathe continuously and end the set before technique starts to break down.

Choose a resistance that lets you preserve technique from start to finish. You should feel most of the work in abdominals, biceps and forearms; if you feel sharp pain, joint pinching or a clear loss of control, reduce the load or range and stop if symptoms persist. On unstable surfaces, master the position with light resistance first; stability should limit difficulty before load does.