Sit on a bench or stable surface with feet flat and slightly apart. Hold a kettlebell in one hand and place the elbow of that arm against the inside of your thigh for support. Let the arm fully extend downward so the kettlebell hangs near the floor while keeping your torso slightly leaned forward and your core braced. Curl the kettlebell upward by bending only at the elbow, keeping your upper arm fixed against your thigh. Squeeze the biceps at the top of the movement, then slowly lower the kettlebell back to the starting position under full control. Repeat for all reps before switching sides.
Log your kettlebell concentration curl sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.