What is fear?
Wikipedia defines fear as... an emotion induced by a threat perceived by living entities, which causes a change in brain and organ function and ultimately a change in behavior, such as running away, hiding or freezing from traumatic events. Fear may occur in response to a specific stimulus happening in the present, or to a future situation, which is perceived as risk to health or life, status, power, security, or, in the case of humans, wealth or anything held valuable.
An emotional response
The fear response arises from the perception of danger leading to confrontation with or escape from/avoiding the threat (also known as the fight-or-flight response), which in extreme cases of fear (horror and terror) can be a freeze response or paralysis.
This emotional response is not necessarily conscious. John was expressing his concern regarding his ability to physically do the more demanding parts of his job. Fear of re-injury with performing more physically demanding tasks is not uncommon following a physical Injury. John may not be able to articulate this. So John avoids.
Fear & avoidance
It is also not uncommon following a physical injury to avoid the potentially harmful tasks as described in the "flight" response. Or John becomes angry when questioned about a more physically demanding task "Are you kidding me, I can't go back to work right now! There is no way!”.
As clinician's, are we ignoring the obvious? Whose job is it to determine the underlying barriers that are affecting our client's?
Please read previous post The Moral Dimensions of Functional Assessment.