This is a very complex part of the workers compensation law in Arizona. It stands for the proposition that a worker's job may place him or her at increased risk of injury just because of the inherently dangerous nature of the job. It's really too complicated to explain in a simple blog post, but let me give two examples:
1. A recent case we had where a worker was on top of a pile of trash on the back of a truck and fell to the ground, sustaining a severe injury. The employer tried to argue that he was diabetic and had probably fainted due to his diabetes which caused him to fall. We argued that, even if that were the cause of the fall, the fact that his work placed him in a dangerous position was the real cause of the injuries, not necessarily the fall. If he were at home sitting on the couch, he wouldn't have been injured.
2. A case I handled a few years ago where a truck driver had a heart attack and ran his truck into a mountain and died. Again, the heart attack itself had nothing to do with his work, but the fact that he's driving 80,000 pounds of cargo 70 miles an hour places him at a greater "positional risk", making the effects of the injury compensable. Again, if he were sitting on his couch at home when the heart attack occurred, he would probably still be with us today.
Just a little interesting part of Arizona Workers Compensation Law from us at Snow, Carpio, and Weekley.