When doing an undulating workout do you take all 3 sets of 3x15 to failure then the next workout do you take all five sets of 5x5 to failure and all four sets of 4x10 to failure (different days?) Is this a good system for mass and strength?
Undulating periodization doesn’t necessarily mean taking things to failure. You can - just like you can in linear periodization or the conjugate method. Rarely do I take anything to absolute failure. If you’re looking for mass - eat more. If you’re looking for strength lift heavy weight and keep the reps lower.