Picture Source: Getting Stronger by Bill Pearl and Gary T. Moran, Ph.D.

you can use either a barbell or a dumbbell.
Starting position-  place your feet about shoulder width apart and bend over and grab the bar over-handed a little wider than shoulder width.
Movement- staying in the bent over position, bring the bar to your upper abdomen (not to your chest) and hold for a second.
Note- keep your back straight and flexed and your head up looking straight ahead.  These are also very good when done with dumbbells.  Use a flat bench to support both your left knee and hand while you lift the dumbbell from the floor with your right hand.