In a within subjects design, all participants are exposed to all levels of the independent variable. A major concern to the participants going through all levels of the independent variable is becoming tired of participating in the study. What disadvantage is being described here?

Fatigue

Explanation:

Participant may become bored,fatigue and tired and might loss interest in taking part in within subjects design.

Engaging a participant  in one condition can impact the performance or behavior on all other conditions, a problem known as a carryover effect due to fatigue.

So for instance engaging a  participants  in high jump might have an impact on their later performance in track race and may even affect their performance on later memory tests.