Kinetic Chains and Movement Principles

What type of force is transmitted from muscle to bone via tendons?

Which of the following is NOT a factor influencing the mechanical advantage of a muscle?

What is the term for the turning effect of a force around an axis?

In a second-class lever, where is the resistance force located relative to the effort force and the axis?

Which of the following is an example of a third-class lever in the human body?

What is the primary function of the core muscles during occupational tasks?

Which of the following accurately describes the arrangement of forces in a first-class lever?

What is the primary function of levers in the human body?

What characterizes a closed-chain movement?

Which statement about tensile force is accurate?

What effect does a longer moment arm have on muscle action?

During which task is the lower limb typically in a closed-chain position?

Which is an accurate description of resistance in the context of force?

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.

Explore the concepts of kinetic chains, including open and closed chain movements. Understand the principles of physics that apply to human motion and the interaction of forces within the musculoskeletal system. Test your knowledge on how these movements affect human performance.