MOVEMENT ANALYSIS

Motor Unit

T.4.1 Neuromuscular Function

4.1.1 A motor unit

• Afferent neurons: Neurons that carry sensory information

• Efferent system: The motoneurons that carry information to the muscles

• Motor unit: a single motoneuron and the muscle fibres which it innervates

4.1.2 Role of neurotransmitters in muscle contraction

• Acetylcholine: is the substance the nervous system uses to activate skeletal muscles, a kind of striated muscle. These are the muscles used for all types of voluntary movement

• Cholinesterase: for the muscle to relax afterward, rather than remaining locked in a tense state, the acetylcholine must be broken down by a cholinesterase.

4.1.3 muscle contraction: sliding filament theory

4.1.4 Type of fibres / motor unit

• Type I - slow twitch muscle fibres and slow nerve transmission speeds and small muscle forces. They can maintain contractions for a long time, as they are fatigue resistant.

• Type IIa - Fast neural transmission time and stronger contraction forces. Also resistant to fatigue.

• Type IIb - Generate the fastest contraction time, but they fatigue at a high rate and so cannot maintain contractions for a long periods of time.

4.2.1 Types of movement of synovial joints

TYPES OF MOVEMENTS.mp4

T.4.2 Joint and movement type

4.2.2 Types of muscle contraction

• ISOTONIC: Muscle shortens, movement occurs, tension remains the same. This movements can be concentric or eccentric (in real life movements is not realistic to think that tension is the same)

• ISOMETRIC: Muscle length remains the same, tension increases. Important in maintaining posture.

• CONCENTRIC: The muscle shortens, beats the resistance.

• ECCENTRIC: The total length of the muscle increases while a tension is produced.

• ISOKINETIC: Muscle contraction with movement, speed stays constant through entire range of motion.

• Resistance will vary

• Adv: Control, low risk of injury

• Dis: Expensive

• MUSCLE RELAXATION:

• The contractile elements are not interlinked by the myosin heads

• The ends of the muscles are not being drawn (or trying to be drawn) together.

• Muscle contraction force is zero

4.2.3 Roles of muscle in joint movement

• AGONIST (MOVER)

• The muscle contracts concentrically to move the bone relative to the

joint.

• The muscle shortens and the muscle torque is greater than any resistance torque.

• Different levels of Agonist: Prime, Assistant and Emergency

• ANTAGONIST

• If the muscle contracts eccentrically to move the bone relative to the

joint.

• The muscle longer even though is contracting.

4.2.4 Reciprocal Inhibition

• It’s an automatic action controlled by neurons.

• When an agonist contracts to move a body segment, it is usual for the antagonist to relax.

• This way the agonist is not being opposed by any muscle torque acting in the opposite direction.

• When the agonist motoneuron is stimulated, the motoneuron to the antagonist is inhibited.

• MISCONCEPTION: Antagonist contracts eccentrically while the agonist contracts

4.2.5. DOMS

• Delayed Onset Muscle Soreness (DOMS)

• Results primarily from eccentric muscle action

• Associated with structural muscle damage, sub-cellular damage (and the associated inflammation)

• Mechanical breaking of actin-myosin bonds + large muscle forces = various biomechanics and mechanical changes in the muscle —> Inflammation stiffness and pain

• Becomes apparent 24 to 48 after exercise, it can last up to 10 days

• PREVENTING DOMS

• Reducing the eccentric component of muscle actions during early training

• Starting training at a low intensity and gradually increasing the intensity

• Warming up before exercise and cooling down after exercise

• TREATING DOMS

• Light exercise

• Non-steroidal anti-inflammatory drugs (NSAIDs)

• Massage

• Ice Baths (Cryotherapy)

T4.3 Fundamentals of Biomechanics

KEY TERMS

SCALAR

Quantity with Magnitude

VECTOR

Quantity with Magnitude and distance.

FORCE (F) -> A vector mechanism. An interaction that will be change the motion of a body.

DISTANCE (d) -> The length of a space between two points

SPEED (s) -> Is the rate at which an object travels a distance. It is measured by m/s.

DISPLACEMENT (s) -> The action of moving an object from its position.

VELOCITY (v) -> The rate at which an object travels, without the measurement of distance

ACCELERATION (s) -> The rate of change of velocity in a unit of time m/s/s.

MOMENTUM (p)

mass (m) x velocity (v)

IMPULSE

Force (F) x time (t)

CENTRE OF MASS

The mathematical point at which the mass of an object is distributed.

THREE TYPES OF LEVERS

FIRST CLASS LEVER:

A first-class lever has the fulcrum in the middle and the load and effort on each side of the fulcrum. Its mechanical advantage is equal to 1

THIRD CLASS LEVER:

These are the levers in which the fulcrum is at one end and the force is applied in the middle and the weight is on the other end

SECOND CLASS LEVER:

Second class lever. In second class levers the load is between the effort (force) and the fulcrum.

NEWTONS THREE LAWS OF MOTION

LAW OF INERTIA: An Object will remain at rest or in constant motion unless acted upon an external force.

LAW OF REACTION: Every action has an equal and opposite reaction.

LAW OF ACCELERATION: A force applied to an object is equal to mass of the object multiplied by the acceleration required.

(F= ma)

APPLICATIONS OF NEWTONS LAWS

RELATIONSHIP BETWEEN AM, MI, AND AV

ANGULAR MOMENTUM (L):

The product moment of Inertia and Angular Velocity

⬇

always constant.

MOMENT OF INERTIA (I):

Tendency to resist angular acceleration

TORQUE: Rotational force

ANGULAR VELOCITY (W):

Rotational speed with direction.

T4.3.11 PROJECTILE MOTION

THE THREE FACTORS OF PROJECTILE MOTION

HEIGHT OF RELEASE

The height above the ground level of the centre of gravity

SPEED OF RELEASE

The force exerted through the object and its centre of gravity

ANGLE OF RELEASE

Ideal angle -> 45º

Affects the path of the projectile.

BERNOULLI PRINCIPLE

"The pressure exerted bu a fluid is inversely related to it's own velocity"

When Airflow in velocity the air pressure is high.

When Airflow Velocity is high the air pressure is low.

Lift force : the fluid flowing around an object exerts a force on it.

Magnus Force: the rotation of an object in motion.

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