For this achievement, you have to complete the 12 exercises that are specific to a Greg Jackson routine. From the main menu, go to the workout menu. You will be presented with the option to pick your trainer and for this achievement, make sure to pick Greg Jackson. You will notice that the first 12 exercises have the trainers face in the bottom right corner of their box, these are the ones you need to select. Once you have done them, the achievement should pop. You can use my tick list to tick off the exercises as you do them so you don’t miss any.