Continuing on from Part 3 of the Deadpool Mega Muscle Mass Workout… Psoas Hip Flexion In most of my clients, I see the unfortunate combination of weak yet chronically tight psoas (hip flexors). So, for this muscle group, I like to combine strength training with an aggressive flexibility routine. So, if you are going to train your hip flexors with this program, you NEED to balance it with some flexibility work. Heavy Partial: N/A Isos: Flexing your hip, push your knee/