Mean Maximal Power, also referred to as MMP, represents that highest average power for a given period. It is used in Xert’s Workout Designer to represent the highest power that is sustainable for a given duration. For example, 20 min MMP represents the highest average power that can be sustained for 20 minutes.
MMP is also used interactively in Xert EBC to represent the highest power that could be sustained for a duration at a given moment. For example, after riding for 12 minutes at an athlete’s 20 min MMP which is, say, 250 W, at that moment, the athlete’ 8 minute MMP would also be 250 watts.
Side note: Although the term MMP is used in Xert, it would be more correctly described as maximal sustainable power, since Xert establishes your power duration relationship based on fresh-to-failure, steady-state efforts and not on average power. Using MMP calculations from regular power data is more commonly used to establish the power-duration relationship, despite its limitations. The term MMP has been chosen because the concept is more readily understandable.