Load-bearing straight arm side lift, side lift, mainly practicing deltoid muscle in the middle of the shoulder, of course, with triceps brachii and forearm muscles.

Also, if you hold your side higher than your shoulders, you will practice your trapezius muscles.

I hope my answer will be helpful to you ~ ~ Please adopt it in time ~ ~ Ask me if you don't understand ~ ~ Hehe, lift your arms straight and horizontally.