Grab a set of dumbbells, and sit on a flat workout bench or on the floor. With one dumbbell in each hand resting on your thighs, lie back on the bench.
Hold the dumbbells above your chest, shoulder-width apart, creating a 90-degree angle between your upper arm and forearm. Your palms should be facing forward.
Press the dumbbells toward the ceiling, fully extending your arms. Hold for one second.
Lower the dumbbells to return to the starting positoin. That's one rep.