The golf swing uses almost every single major muscle group within the body so to have a truly rounded powerful swing you also need to work every muscle in the body. Now you don't have to be muscle bound to the extent that you can't move but you do need to have an appropriate amount of power in each part of the body so nothing is working against each other. Now one of the most important parts for golf swing stability is your back muscle, is your lat muscles across your back will actually give you a lot of support while you're actually swinging and also coming into impact will also help generate power in conjunction with the stomach muscles and the side muscles to actually turn the body through with a lot more energy. Now a greater way to actually work the lat muscles is using a resistance band, and to use some reverse flyes. Now reverse flyes are very easy to do with the resistance bands you get a resistance band depending on your strength is the appropriate resistance that you need to use always kind of check with a health professional first before you do any of this stuff.
But very simply put the one foot down on the resistance band just in the balls of the feet so it's not likely to slip up and hit you in the face this wouldn't be a very happy way to start the morning, but getting it down just on the balls of the feet getting the left leg if you're doing the right leg first slightly bent so your weight is pressing forward down onto the balls of the feet take the resistance bands spread them apart tranking your back straight as you want to in the actual golf swing and then raise up with this direction. Now this is going to work the back muscles, it's going to work the shoulder muscles and it's going to work everything that's going to cause a lot of stability during the downswing. So once more pressing down onto resistance bands back nice and straight raise up, hold for a moment and then relax back down. Now if you can do these exercises, if you can do these only a few times a day you will be able to work most of your body and you will be able to have a much more powerful golf swing.