Active insufficiency, muscles can't go for further shortening while doing the activity on the nearest joint, which the muscle crosses. agonist muscles are mostly showing this phenomenon. let's take the example of flexor compartment muscles of the forearm . flexor compartment muscles of the forearm are responsible for elbow flexion, metacarpal flexion proximal interphalangeous flexion, and distal interphalangeous flexion. if the movement is done as said in the same sequence, the person will feel difficult to flex MCP and fingers after flexing the elbow and wrist, because muscles are already shortened by the elbow and wrist flexion. so further movement is difficult as it is restricted. this is called Active insufficiency