In addition, some women have more developed muscles due to genetic factors, and will also see a relatively large deltoid muscle. 2. It may be due to exercise. If the patient often does activities and exercises involving the shoulder joint, it may cause the deltoid muscle to be larger than normal, for example, you can often see swimmers on TV, the muscles around the shoulder joint are very strong, and the whole shoulder looks very wide. 3. There may be a reason for obesity. Some women have relatively thick subcutaneous fat and too much of it is deposited here, so they may also look and feel like their deltoids are bigger.