Human movement is reciprocal in nature: Opposing muscle groups must coordinate for proper movement.
Muscle length and strength between opposing muscle groups need to be in balance for normal movement and function.
There are two primary types of muscle imbalances:
Body muscular imbalance. The muscles on each side of your body should be symmetrical with each other in size and strength. When a muscle (or muscles) on one side of your body is larger, smaller, stronger, or weaker than the corresponding muscle(s) on the other side, you have a muscle imbalance.
Joint muscular imbalance. Each of the muscles that surround a joint work together with opposing force that keeps the bones of the joint centred for optimum movement. If one or more of these muscles becomes weaker, stronger, looser, or tighter than normal, you have a muscle imbalance and joint movement can be limited.
What causes a muscle imbalance?
A muscle imbalance is often the result of:
- natural development
- certain activities of daily life
- inactivity
- bad posture
- an unbalanced exercise program
- exercising with improper form.
Imbalances can often be corrected through exercise.
Source: https://www.healthline.com/health/limited-range-of-motion