Using a kettlebell for overhead presses might make your shoulder and back muscles work harder than using a dumbbell, because the kettlebell's weight hangs below the handle and makes you stabilize more as you lift.

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.

Using a heavier kettlebell during shoulder presses activates key shoulder-blade muscles way more than a light dumbbell — up to 72% more, according to this claim.

If you're used to lifting weights and do shoulder presses sitting down, using an unstable weight or an unstable surface means you won't be able to lift as much weight.

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.

For guys who lift regularly, the top part of their shoulder muscle (trapezius) works differently when doing overhead presses — it doesn’t ramp up much with kettlebells and doesn’t respond as strongly to heavier weights, which might mean it’s more about keeping things stable than powering the movement.