Levers

Agonist muscle/Primer movers

• Concentrically contracting muscles are ALWAYS agonists

• Gravity can also be a prime mover, when the muscle is moving downward

Antagonist muscle

Fixator muscle

Synergist muscles

Isotonic Contractions

Iso - Same

Tonic - Tension

Tension in the muscle remains constant.

Length of the muscle changes.

Two types:

• Concentric contraction (Shortens)

• Eccentric contraction (Lengthens)

Isotonic Contractions:

• Concentric Contraction

Muscle Shortens

Isotonic Contractions:

• Eccentric Contraction

Muscle Lengthens

Isometric Contractions

Iso - Same

Metric - Length

Tension in the muscle remains constant.

Length of the muscle remains constant.

Open-Chain movements

Not touching the ground

Close-Chain movements

Touching the ground

Levers

First-class lever

A lever where load (resistance) and effort (force) are on opposing sides of the fulcrum (axis).

(e.g see-saw (body example: neck))

Second-class lever

Lever where, from the fulcrum (axis), the effort (force) is applied further than the load (resistance). Amplifies force production.

(e.g wheelbarrow (body example: tip-toeing))

Third-class lever

Lever where, from the fulcrum (axis), the load (resistance) is applied further than the effort (force). Amplifies speed production.

(e.g fishing pole (body example: swinging tennis racket))

Most levers in the body are third-class.

Effort in levers

Located where athlete touches the equipment

Load in levers

Usually comes from an outer object (e.g tennis ball hitting racket)

Mechanical advantage

The amount by which the lever amplifies the force (effort).

Mechanical advantage = force arm/resistance arm = effort arm/load arm

>1 in second-class levers

<1 in third-class levers