Kinesiology Concepts Part II - Biomechanical Foundations (HPOT 6220)

Question-and-answer flashcards covering key concepts from biomechanics notes: forces, Newton's laws, planes/axes, osteokinematic motion, kinetics, force vectors, COG/BOS, force systems, and muscle actions.

What are external forces in biomechanics?

Forces that act on the body from the outside, such as gravity, friction, and surface interactions.

What are internal forces in biomechanics?

Forces generated by muscular contractions that act on bones and ligaments to produce movement.

State Newton's Law of Inertia.

An object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force.

State Newton's Law of Acceleration.

Acceleration is directly proportional to the net external force and inversely proportional to the mass.

State Newton's Law of Action-Reaction.

For every action, there is an equal and opposite reaction, resulting in a net zero external force when both occur.

What is osteokinematic motion?

Movement of bones at joints, including angular and linear motions.

Differentiate angular (rotary) motion and linear (translatory) motion.

Angular motion changes joint angles (flexion/extension, abduction/adduction, rotation, circumduction); Linear motion involves movement along straight or curved paths without angular change.

What is rotation vs circumduction?

Rotation is a circular movement around an axis; circumduction is a circular motion around an axis in the shape of a cone.

Which types of motion do most activities involve?

Both angular and linear (osteokinematic) motions.

Cervical flexion occurs in which plane and about which axis?

Sagittal plane around a frontal (mediolateral) axis.

Cervical lateral flexion occurs in which plane and about which axis?

Frontal plane around a sagittal axis.

Define open kinetic chain (OKC) and closed kinetic chain (CKC).

OKC: distal segment free to move (e.g., knee extension). CKC: distal segment fixed to a surface (e.g., squat).

What is the study of kinetics?

The study of forces acting on mechanisms and bodies during movement.

What are the components of a force vector’s point of application?

The exact location where the force is applied on the body or segment (external or internal).

What is the line of pull in a force vector?

The direction from muscle insertion toward the proximal attachment (origin), indicating the path of force.

What does the magnitude of force refer to?

The amount of force required to overcome existing external forces such as gravity and friction.

What happens when the angle of pull is less than 90° at a joint?

It creates a compressive (stabilizing) force at the joint.

What happens when the angle of pull is greater than 90° at a joint?

It creates a distractive (destabilizing) force at the joint.

What is considered the most efficient position for movement and load bearing around a joint?

Approximately 90° between the line of pull and the mobile segment.

What are Gravity, Center of Gravity (COG), and Base of Support (BOS)?

Gravity is an external force; COG is the point where body parts balance; BOS is the part of the body in contact with the supporting surface.

Where is the center of gravity located in anatomical position typically?

Anterior to S2 (location varies by person and body segment).

What is the Base of Support (BOS)?

The part of the body in contact with the supporting surface; stability increases when COG is inside BOS.

What does it mean if the COG is outside the BOS?

More muscular force is required to maintain balance; the person is in a relatively unstable position.

What is a parallel force system (external vs internal)?

External: two or more forces in the same plane, same or opposite directions. Internal: forces generated by muscles (e.g., abdominal muscles and paraspinals).

What is a force couple?

Two or more muscles that generate forces in different directions simultaneously to produce rotary movement.

What is a concurrent force system?

Two or more internal forces act at a common point but in divergent directions, producing combined movements (e.g., shoulder flexion and extension components).

What are the primary functions of skeletal muscles?

Produce movement, stabilize posture, assist with circulation, and perform thermogenesis.

What is muscle tone?

A state of readiness to perform a task, reflecting the ability to maintain and adjust posture and movement based on task, environment, and individual.

What are the main types of muscle contraction?

Isometric (no length change), isotonic (length changes with joint angle change; concentric and eccentric), with concentric shortening and eccentric lengthening.

Define isometric contraction.

Muscle produces stabilizing force without changing length.

Define concentric contraction.

Muscle shortens, producing movement and acceleration.

Define eccentric contraction.

Muscle lengthens while controlling movement (deceleration).

What are the five muscle action roles?

Agonist (prime mover), synergist (assists), antagonist (opposes, relaxes for action), neutralizer (prevents unwanted motion), stabilizer (supports to allow efficient action).

What is a prime mover (agonist) in skeletal muscle action?

The primary muscle responsible for producing a movement.

What is a synergist in skeletal muscle action?

Muscles that assist the agonist in producing the main action.

What is an antagonist in skeletal muscle action?

A muscle that performs the opposite action and must relax to allow the agonist; involves reciprocal inhibition.

What is a neutralizer in skeletal muscle action?

Prevents unwanted motion from muscles that have more than one action.

What is a stabilizer in skeletal muscle action?

Supports the body to allow the agonist to work more efficiently; prevents unwanted motion at a joint.

What does bench press illustrate about muscle contractions?

Concentric contraction during the lifting phase and eccentric contraction during lowering (example of muscular action in a common exercise).

How are open and closed kinetic chain exercises defined in practice?

OKC: distal segment is free to move; CKC: distal segment is fixed to a surface, causing movement with fixed contact.