About shoulder exercises you should always keep in mind the following: When you raise your arm, the shoulder blade is always rotated, right from the beginning of the movement. This movement also involves other muscles such as the trapezius and the serratus anterior muscle. So, all these muscles always take part in any shoulder exercise.
Shoulder exercises weights note: We would like to emphasise that during training, athletes often choose to use heavier weights rather than performing the correct exercises, thereby using muscles that they don't intend to train and running pointless risks. A typical example is the "lateral raises with dumbbells” shoulder exercise. In fact, if you use weights that are too heavy while performing such kind of exercise, you will have trouble raising the dumbbells to the proper level (indicated by holding the hands out level with the shoulders). This will put excessive pressure on the lumbar muscles and risk damaging your spine. Make your shoulder muscles training efficient and safe - choose the sufficient weights, and perform exercises correctly.
Shoulder muscles: the deltoid muscle, which covers the area commonly referred to as the shoulder, is roughly divided into three parts: the anterior deltoid, the lateral deltoid and the posterior deltoid. Each of these is further divided into at least seven other muscle fibres. The deltoid muscle raises the arm and moves it like a crane in any direction, while the anterior part of the muscle serves to rotate the humerus towards the outside. You can find more about shoulder anatomy on wikipedia.
