The terms function and functional can be confusing because function can be intrinsic, extrinsic, or even a combination of both.  The term ‘functional’ has been used to describe an approach to exercise prescription that tries to reproduce the same movements used in a functional activity.  This is an extrinsic viewpoint of function.  Janda’s viewpoint of function is intrinsic and relates to the function of ‘structures and systems’.  The intrinsic viewpoint of function includes the three processes of physiological, biomechanical, and neuromuscular function.  Understanding the underlying functions of these three processes is the key to understanding functional lesions.

• Physiological function is the response of tissue to dysfunction and damage as well as the healing process.  It is important to understand the consequences of dysfunction and the process of rehabilitation.
• Biomechanical function includes the osteo- and arthrokinematics involved in human movement and the resulting force vectors imparted on human tissue.  Recognition of the biomechanical function of structures assists clinicians in understanding the concept of chain reactions and how the entire kinetic chain is involved in both movement and pathology.
• Neuromuscular function relates to the ‘sensorimotor’ aspects of movement such as proprioception and reflexes, which are keys to the processes of motor control and motor relearning in effective exercise prescription.

Excerpted from:  (Page, Frank, Lardner.  Assessment and Treatment of Muscle Imbalance, The Janda Approach.  2010, Human Kinetics, Champagne IL.)