There are four main reasons why your muscles cramp and here is what you can do about them 1 Muscular imbalance Some muscles work harder than they should while others barely contribute Overworked muscles fatigue and cramp while weak underactive muscles can seize up the moment you ask them to do their job 2 Poor blood flow Tight compressed muscles limit circulation When blood and oxygen cannot reach the tissue properly waste products build up and cramps follow 3 Nervous system overload Stress anxi