What is the test for establishing that a plaintiff has failed to mitigate his loss of income due to chronic pain?

I choose to note here that the defendant has not established that the plaintiff has failed to mitigate his loss. The defendant must establish that the plaintiff has acted unreasonably and that if the plaintiff had done what he has unreasonably failed to do his condition would be better than it is: Byron v. Larson, 2004 ABCA 398. In this connection the defendant refers to the evidence of Dr. Hamm (Exhibit 2 Tab 2 Page 14 paragraph 13) and to his recommendation that the plaintiff seek the services of a personal trainer, attend at a gym or community centre on a regular basis and have the benefit of pain management counselling “particularly to optimize his adjustment to his chronic pain pattern”.