This is a dynamic exercise helping to correct that common upper body misalignment.
What this is good for:
Opening the chest, stretching the shoulders, and the biceps.
How to practice:
Stand looking straight ahead, feet shoulder-width apart and arms by your sides. Clasp your hands behind your back with thumbs pointing towards the floor, Stand tall, open your chest and move your hands back and towards the ceiling. Stop when you feel a stretch in the shoulders and biceps muscles.
Hold this position for, say 30 seconds. Then rest, and repeat a couple of times.
Build the repetitions over time, and the regularity of performing this exercise.