There are many causes of muscle pain.  Tension, stress, overuse and minor injuries are some of the most common causes of normal musculoskeletal pain. This pain is usually in one spot, but can sometimes affect several muscles.  This is different than Systemic muscle pain. Systemic muscle pain is usually felt throughout your entire  body and is commonly caused by some kind of infection or organic disease.
It is important to differentiate these two types of pain so that you can decide the type of care your body might need. If it is normal musculoskeletal pain there are many different types of therapies you can try. Massage, ultrasound, TENS are some ways that you can decrease muscle pain.
An even more effective method to treat muscle pain is Active release technique. Active release technique is more commonly known as A.R.T and is commonly used to loosen up muscle tissue and decrease joint stiffness and muscle pain.
Active release technique works by using hand pressure to break of fibrous adhesions and trigger points. By using stretching motions and hand pressure in the direction of venous and lymphatic flow it will release tightness in muscle and create more oxygen to the tissue. Creating more oxygen to the tissues allows the tissue to heal quicker and creates less tightness and stiffness in muscles.