Should the incentive of research be discussed in the literature survey?
Since you are doing a "thesis project", which seems to be a rather particular kind of writing, you should probably ask your advisor what exactly they expect of you concerning the literature review.

In general, though, normally a literature review for such a topic should mainly cover other research that is related to your topic. Specifically, I would consider surveying research on:


other technical systems that encourage people to exercise;
other systems or approaches (non-technical) that encourage people to exercise;
other research that is generally similar to what you are doing, with "similar" being fairly broadly defined.


In general, I wouldn't expect that you would need to do anything about the advantages of exercise--that is well known and understood, and extremely general. 

All that said, again, you should ask your advisor what exactly they expect.