Kinetic chain is a term used to describe the way a human body moves. It's especially relevant in physical therapy, sports medicine, neuro-rehabilitation, prosthetics, orthotics, and other areas of medicine that focus on the musculoskeletal system.
The basic concept is one most people are familiar with from an old song: the hip bone's connected to the thigh bone, the thigh bone's connected to the knee bone, etc.
When you move one of those bones, it creates some kind of movement or effect—large or small—in adjacent, nearby, and sometimes even not-so-nearby bones (and the muscles and connective tissues that interact with them).
This happens as a chain reaction. Medicine borrowed the engineering term kinetic chain to describe this set of linked movements.
The concept of the kinetic chain applying to the human body was first put forth in 1955 by Dr. Arthru Steindler based on the theory of mechanical engineer Franz Reuleaux.
The Kinetic Chain: A Living Example
To get a real-life example of the kinetic chain in action, let's think about what happens when you walk:
You step forward with your right leg.
That causes your pelvis to rotate forward on the right side and backward on the left.
Because the pelvis is part of the trunk, the trunk automatically moves forward, as well.
Your spine turns toward the right leg and the pelvis as they extend forward, which allows you to continue facing forward as you walk and see where you're going.
Each of these movements causes another. Some of the reactions are automatic, such as #2, while others are a reflex, such as #4.
A kinetic chain can be described as either upper or lower. Kinetic chain exercises are either open or closed.
Upper Kinetic Chain
The upper kinetic chain comprises:
Lower Kinetic Chain
The lower kinetic chain is composed of:
Open Kinetic Chains
A kinetic chain is considered "open" when the part of the body you're moving (typically a limb) is loose in space. In other words, the hand or foot is free to move and not pressing against a surface. This allows a muscle or muscle group to act in isolation.
Common examples of open kinetic chain movements include:
Bicep or leg curl
Raising your arms over your head while sitting in a chair
Lifting a leg while lying on your back
Waving a hand
Extending the lower leg from the knee while sitting
Open kinetic chain exercises have several things in common.
They're typically characterized by rotation at the primary joint, although rolling and other types of movement may also occur.
Usually, only one segment moves at a time (for example, while extending the lower leg from the knee, the lower leg moves but the upper leg remains stationary.)
Only the muscles associated with one joint are involved.
Open kinetic chain exercises can be used to improve the strength and function of an isolated muscle or muscle group.1
This can be beneficial early in a rehabilitation program or when improving aesthetics, such as for a bodybuilder. However, closed kinetic chain exercises may be more beneficial in some circumstances.
Closed Kinetic Chains
A kinetic chain is considered "closed" when the body part you're using (again, usually an arm or leg) is fixed against a hard, unrelenting surface.
When the body part is pressed against a wall or the floor, for instance, resistance is sent back into your trunk. The body parts through which the resistance moves make up the components of the chain for that particular movement or exercise.
Examples of closed kinetic chain exercises include:
Yoga cat-cow stretch
Characteristics of closed kinetic chain exercises include:
Linear stress patterns
Movement occurring at multiple joints and multi-joint axes
Simultaneous movement of more than one segment
Promotion of joint stabilization
Because multiple segments are in motion, more muscles contract at the same time in order to stabilize and control movement across multiple joints.
Closed kinetic chain movements are often used to strengthen core muscles and stabilize posture. A benefit of closed kinetic chain exercises is that the movements they promote often relate better to activities of daily life, so they're considered more "functional."1
Sometimes, in rehabilitation, a person will use open chain exercises to strengthen an isolated area, then move on to closed chain exercises.