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.

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.

If you're already strong and used to lifting, doing overhead presses with shaky weights or on wobbly surfaces probably won't help you build more muscle or get stronger — and you'll likely end up lifting less weight overall.

Doing certain shoulder exercises like behind-the-neck pulldowns or military presses might increase your risk of shoulder instability, but strengthening the external rotator muscles could help protect your shoulders.

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 guy who lifts weights, doing the back-overhead press might fire up your rear shoulder and triceps muscles more than the front version when you're lowering the weight.