This is the range of motion a joint can move in under no load or tension under external control, such as another person or gravity. This range of motion is limited purely on structure and tissue.
This is the range of motion you can produce at a joint under your own control without losing joint integrity. This range of motion is limited by your own muscular contractions. Weakness or instability will limit your range by inhibiting contractions at points of the range where the joint is no longer stable and under muscular control.
This is the range of motion you are capable of producing yourself under load while maintaining joint integrity and function of the stabilizing muscles and prime movers. As load increases your ability to stabilize a joint in certain ranges may be lost thus reducing the available range of motion.
When you lose range of motion under a certain load, it means you have reached the maximum load in which you can stabilize your entire active ROM. The stronger and more neurologically efficient your stabilizing musculature the closer your loaded active ROM will be to your active ROM. Your loaded active ROM will never exceed your active ROM (see Forced ROM).
Conditional Ranges of Motion
This is the passive range of motion a joint can be forced into under a load. This is evident when adding load increases your range of motion beyond your unloaded active range of motion. Increased load will stress passive structures into more range of motion if you let it, and can often give the appearance of proper form.
When there is a desire to have a greater active ROM this can be very misleading. As that load pushes you outside of your active range of motion, more force is shifted onto surrounding muscle groups and passive structures rather than the prime movers. In fact in an effort to protect the joint, the primary torque producing muscles around the joint will be inhibited by the nervous system in an attempt to protect the joint integrity. This ultimately leads to loss of active ROM over time.
There are two keys to developing the most efficient motor unit recruitment patterns.
Always training in the appropriate ROM for the load you are using.Proper execution of the exercise through proper intent and technique.