Kinetic Chains and Movement Principles

Kinetic Chains

• The cooperative, interdependent movement of the segments and joints of the body is referred to as a kinetic chain.
• Kinetic chain occurs in both closed-chain and open-chain movements.

Closed-Chain

• Proximal (distal) segments moving in relation to a fixed, nonmoving distal segment.
• For example, imagine squatting planted on the ground, creating closed kinetic chain.
• Pushing the body toward your hips and knees flex to lower extremities as the fixed position of the feet.

Open-Chain

• Moving the distal body segments in space, allowing joints to move together or independently.
• For example, the arm can move freely in space, independently from other parts of the body.

Principles of Physics

• Force, moment, levers—all concepts, from physics.
• Essential when considering the musculoskeletal systems acting internally or externally.

Force

• Any push or pull of matter.
• In humans, force occurs in the form of tensile force (pulling) or compressive force (pushing).
• Tensile force occurs between anatomical structures in the body.
• Compressive force occurs between muscle tissue and bone.
• Motor performance skills (e.g., reaching, lifting, and transporting) involve external resistance.
• Resistance must be overcome by effort.
• The internal force needed to overcome resistance is referred to as exerted force.

Moment

• The moment (action) of a muscle is affected by the distance between the muscle and the joint.
• The farther the muscle is from the rotational axis (joint), the greater the mechanical advantage.

Levers

• Levers or pulley systems are functional mechanisms in the body.
• Classified by the arrangement of effort (muscle) and resistance.
• First-class lever—exerting force and resistance on opposite sides of the axis. Example: cervical spine.
• Second-class lever—resistance being closer to the axis. Example: ankle.
• Third-class lever—effort being closer to the axis. Example: elbow.