Hi, I am totally new to yoga and wondered, which exercises would be best for improving back posture and strengthening the back muscles? Thank you for your help in advance.
Emma
I used to have an extremely severe sway back when I started doing yoga, I find that plows and spinal twists have helped my back immensely!
Hello Emma,
Two part question?
For improving the posture one needs to determine what thingies are taking the posture away from it’s natural state. Ergo it is important to see the student before making suggestions. No one suggestion will fit all people.
If your posture is being wrenched by tight chest muscles and the withdrawal of the heart toward the back body - one answer. If the muscles in the upper back are weak, another answer.
Poses that will strengthen the back would be Makarasana, Salabhasana, Sarpasana, and in some cases Bhujangasana. Back strengthening poses should not be confused with back bending poses even though some back bending poses do serve to strengthen the back muscles.
If you are totally new to the practice please go ease/slowly/mindfully into the beginning chapter(s) of your practice. Find a sound teacher and maintain your urge to grow and willingness to change - then of course patience must be mastered 
By practicing the Locust Pose is great for strengthening the back muscles, buttocks, arms and legs. Locust Pose should be avoided if you have a headache, a serious back injury or neck injury.Completely avoid doing Locust Pose if you have a chronic backache, particularly resulting from a spinal problem.