Testovance To achieve maximum contraction of the posterior bundle of deltas, middle trapeziums and the rhomboid muscle, you can only wind your elbows as far behind your back as possible. Too heavy weights in exercise are useless. They will not allow you to spread your arms at maximum amplitude, which will significantly reduce the effectiveness of the exercise. The secret to the success of reverse dilutions lies precisely in the technique of performing the exercise. Increase weight only when you feel that your technique is perfect. A variation on the back grip exercise is possible when the thumb is looking down. This turns the elbow to the top and isolates the back deltas as much as possible.