As I train various muscle groups, I've noticed that I cannot flex a few of them the way I would biceps or quads. The flex becomes painfully tight verging on a muscle cramp before I finish the range of motion. Potential causes I thought of:
- The opposing muscle group is over-relaxed, allowing this muscle to overtighten
- The brain is not familiar with the movement and is allowing a tighter contraction than is safe
- My musculo-skeletal structure is weird
This has been happening with various movements such as external hip rotation, shrugs behind the back, and torso twists -- small, seldom-used muscles. Should I just keep flexing them so the brain can learn to use them normally?