You don’t even need to use weights to strengthen your back. Sometimes the most resistance you need is your own body. In our sedentary society, it is common to see the shoulders slump forward. Dr. Brett McIff with the Utah Department of Health shows how you can fight back against this by doing shoulder drawbacks.
Sit on a chair with tall posture, back away from the chair. Raise your arms in front of you to shoulder height. Keeping your posture tall, bend your arms as you pull your elbows back behind you as far as you can. Hold it there for about a second or two, then return to the start position. Repeat 8-12 repetitions, 1-3 sets.