When healthy guys do shoulder presses, standing with dumbbells makes their shoulder muscles work harder (based on electrical activity), even though they can lift heavier weights when sitting with a barbell.

If you're a healthy guy doing dumbbell shoulder presses, sitting down might work your rear shoulder muscles a bit more than standing up—about 15% more, according to muscle activity readings.

If you're a healthy guy doing seated shoulder presses with heavy weights, using dumbbells probably works your front shoulder muscles a bit more than using a barbell.

When competitive male bodybuilders do overhead presses with a free barbell instead of a machine, their side and rear shoulder muscles work harder because they have to balance the weight themselves.

When guys who lift weights do shoulder presses sitting down with a kettlebell instead of a dumbbell that weighs the same, their shoulder and back muscles seem to work a bit harder — maybe because of how the kettlebell is shaped and balanced.

If you're a guy who lifts weights, the shoulder press works your front shoulder muscle more than bench presses, flys, or lateral raises when doing a typical workout.