Biomechanics of Resistance Exercise

Key Terms Range of Motion

Movement Planes

Muscle Actions

Anatomical LocationsKey Terms

• Midline: The invisible line that divides the body or a single body part in half down the center.

• Anterior: The surface of the body that would be considered the front.

o The pectorals are on the anterior aspect of the body

• Posterior: The surface of the body that would be considered the back.

o The rhomboids are on the posterior aspect of the body

• Superior: Toward the head or upper part of a structure:

o The humerus is superior to the radius

• Inferior: Toward the lower part of a structure

o The tibia is inferior to the femur

Anatomical LocationsKey Terms

• Medial: The surface that is closer to the midline of the body.

o The adductors are medial to the abductors

• Lateral: The surface that is further from the midline of the body.

o The abductors are on the lateral aspect of the leg

• Proximal: Closer to the origin of a point of reference

o The elbow is proximal to the wrist

• Distal: Further from the origin or point of reference

o The foot is distal to the knee

Muscle MovementsKey Terms

• Agonist- (prime mover) the muscle most directly involved in bringing about a movement

• Antagonist- the muscle that slows down or stops the movement. Opposes the agonist muscle

• Synergist- Assists indirectly in a movement

• Muscle origin (proximal attachment)- the point closest to the midline of the body where the

muscle attaches to the bone

• Muscle insertion (distal attachment)- the point farthest from the midline of the body where the muscle attaches to the bone

• Stabilizer muscles- muscles acting in a stabilizing role that aren’t directly involved in lifting a

weight, but instead keep certain parts of the body steady so that the primary working muscles

can do their job properly.

• Anatomical Position- The body is erect, the arms are down at the sides, and the palms face forward.

Examples of Agonist vs. Antagonist Muscles

Agonist (Prime Mover) Antagonist

Biceps Triceps

Deltoids Latissimus Dorsi

Pectoralis Major Trapezius/Rhomboids

Rectus Abdominis Erector Spinae

Quadriceps Hamstrings

Types of Muscular Contractions

• Concentric Muscle Action- A muscle action in which the muscle shortens because the contractile force is greater than

the resistive force.

• Eccentric Muscle Action- A muscle action in which the muscle lengthens because the contractile force is less than the resistive

force.

• Isometric Muscle Action-A muscle action in which the muscle length does not change because the contractile force is equal to

the resistive force.

The Three Movement Planes

• Sagittal Plane: Divides the body into right and left parts.

o Primary movements include Flexion and Extension

•  Frontal Plane: Divides the body into anterior and posterior parts.

o Primary movements include Abduction, Adduction, and Lateral Flexion

•  Transverse Plane: Divides the body into superior and inferior parts.

o Primary movements include Pronation, Supination, and any rotation about a vertical axis.

Movement Planes Anatomical Position

Anatomical Planes divide body or joint into 3 segments:

Sagittal

Frontal/Coronal

Transverse/Horizontal

Basic Description of Movement

• Flexion : Decreasing the angle of a given joint.

• Extension : Returning a joint from flexion.

• Abduction : Movement away from the midline in the frontal plane.

• Adduction : Movement toward the midline in the frontal plane.

• Rotation : Movement counterclockwise or clockwise about a vertical axis

• Pronation: Internal rotation resulting in appendage facing downward

• Supination: External rotation resulting in appendage facing upward

Examples of Planes and Motions

Plane Motion Example

Sagittal Flexion/Extension Walking, squatting, overhead press Frontal Abduction/adduction

Side Flexion

Star Jump

Lateral Arm Raise

Transverse

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