Start with feet under hips, core engaged, hold a dumbbell in each hand at your sides, palms facing outward (underhand grip or supine curl).
Keeping your elbows locked by your sides, squeeze your bicep muscle to curl the weights up to shoulder-height as you exhale.
With control, slowly lower the dumbbells down half way, stopping when your elbows form a 90 degree angle.
Then curl the dumbbells back up to shoulder height.
And finally lower the dumbbells all the way back down to your thighs, returning to starting position.
Think: all the way up, halfway down, back to the top and all the way down.