Some key Performance Menu terminology:

AKP – Ass-Kicking Potential. The extent to which something or someone can and will kick ass.

DOS – Degree of Suck. Unit of measurement for an exercise or workout's difficulty.

Note that often AKP and DOS are mistakenly used interchangably. To be effective, an exercise or workout with a high DOS must also have a high AKP. High DOS with low or no AKP is simply torture.