Massages have been used to treat muscular pain and to promote recovery from injuries. However it is still relatively little understood and has not been researched scientifically to a great extent due to the nature of the treatment itself. However much of the research conducted in this field especially regarding muscular fatigue has been promising.
Muscular fatigue especially caused due to exercise or other physical activity causes minuscule tears leading to the body then acting to treat them. This causes inflammation in the muscles. A study conducted in 2012 seems to suggest that massage can help in controlling the production of cytokines that are critical in causing inflammation. Massage also promotes mitochondria growth which helps in breaking down glucose to release energy thereby promoting muscular recovery. However the results of these studies should be taken with a grain of salt as they have been disputed on grounds of small sample and drawing conclusions from insufficient evidence.
Other studies have indeed found there to be reduction in perceived fatigue along with increased blood flow and reduced blood pressure. The secret may also lie in human neurology that is programmed to react positively towards touch and sensitivity.
In conclusion massage indeed helps in reducing perceived levels of muscular fatigue even if the science behind it is not well understood, the biggest key is making sure that the person performing any massage has been through the right massage courses and knows what they are doing.