Sport Books Publisher 1

Muscle Teamwork Agonist (prime mover):

- the muscle or group of muscles producing a desired effect

Antagonist:

- the muscle or group of muscles opposing the action

Synergist: - the muscles surrounding the joint being moved

Fixators:

- the muscle or group of muscles that steady joints closer to the body axis so that the desired action can occur

Sport Books Publisher 2

Bending or straightening of elbow requires the coordinated interplay of the biceps and triceps muscles

Sport Books Publisher 3

Contractile Machinery:

Sarcomeres Contractile units Organized in series ( attached

end to end) Two types of protein

myofilaments:

- Actin: thin filament

- Myosin: thick filament Each myosin is surrounded by

six actin filaments Projecting from each myosin

are tiny contractile myosin bridges

Longitudinal section of myofibril

(a) At rest

Sport Books Publisher 4

High microscope magnification of sarcomeres within a myofibril

Sport Books Publisher 5

Contractile Machinery:Crossbridge formation and movement Cross bridge formation:

- a signal comes from the motor nerve activating the fibre - the heads of the myosin filaments temporarily attach themselves to the actin filaments

Cross bridge movement: - similar to the stroking of the oars and movement of rowing shell- movement of myosin filaments in relation to actin filaments- shortening of the sarcomere- shortening of each sarcomere is additive

b) Contraction

Longitudinal section of myofibril

Sport Books Publisher 6

Contractile Machinery:Optimal Crossbridge formation

Sarcomeres should be optimal distance apart

For muscle contraction: optimal distance is (0.0019-0.0022 mm)

At this distance an optimal number of cross bridges is formed

If the sarcomeres are stretched farther apart than optimal distance:

- fewer cross bridges can form less force produced

If the sarcomeres are too close together: - cross bridges interfere with one

another as they form less force produced

Longitudinal section of myofibril

c) Powerful stretching

d) Powerful contraction

Sport Books Publisher 7

Contractile Machinery:

Optimal muscle length and optimal joint

angle

The distance between sarcomeres is dependent on the stretch of

the muscle and the position of the joint

Maximal muscle force occurs at optimal muscle length (lo)

Maximal muscle force occurs at optimal joint angle

Optimal joint angle occurs at optimal muscle length

Sport Books Publisher 8

Muscle tension during elbow flexion at constant speed

Sport Books Publisher 9

Contractile Machinery:

Tendons, origin, insertion

In order for muscles to contract, they must be attached to the bones to create movement

Tendons: strong fibrous tissues at the ends of each muscle that attach muscle to bone

Origin: the end of the muscle attached to the bone that does not move

Insertion: the point of attachment of the muscle on the bone that moves