Lie face‑up on the floor with one foot placed on a stability ball and your arms by your sides. Lift your hips into a bridge position, keeping your body in a straight line. From here, bend the working knee to roll the ball toward your glutes, focusing on squeezing the hamstrings. Slowly extend your leg to push the ball back out while keeping your hips elevated and core engaged throughout the movement.
Log your straight hip single leg curl on stability ball sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.