Lie on your back with knees bent and feet flat on the floor, holding a dumbbell against your chest. Engage your core and lift your upper body toward your knees by curling your shoulders off the ground. Pause briefly at the top while squeezing your abs, then slowly lower your torso back down in a controlled motion. Keep your lower back pressed to the floor and avoid using momentum.
Log your dumbbell crunch up sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.