IB Sports Science Midterm Understandings Review

Muscular Function

The body uses different types of muscular contractions to create movement and stability. Each type of contraction has a different function.

Motor Units

Muscles are organized in functional groupings called motor units that contract using the all-or-none principle.

Muscle contraction requires…

the metabolism of ATP within the muscle cells

Acetylcholine

A neurotransmitter stimulating skeletal muscle contraction

How are motor units differentiated?

• By fiber type and neuron diameter

• Order of types of muscle contractions from least to most intensity

Motor Unit Types

Type I, Type IIa, Type IIx

Type I

slow to contract, but highly resistant to fatigue (slow twitch) - first to be recruited when activating a muscle, for low intensity, long duration activity, slow twitch, low force, aerobic (uses oxygen) ex. walking/long distance running

Type IIa

Second to be activated, fast twitch, recruited for medium to high intensity activities, both aerobic and anaerobic ex. jogging, lifting weights

Type IIx

Last to be activated, large fast twitch muscle fibers, activated for high-force and high power activity, fatigue fast, largest motor neurons, high intensity, short duration, anaerobic (doesn’t use oxygen), ex. sprinting

How do their recruitment patterns vary?

Their recruitment patterns vary depending on the activity, the principle of orderly recruitment. As the intensity of the activity increases, muscle contraction involves progressive recruitment of type I to IIa to IIx.

What can cause alterations in a motor units recruitment pattern?

Hypertrophy and Atrophy

Hypertrophy (muscle growth)

increase in muscle size and strength due to exercise (anabolism)

Atrophy (muscles shrink)

decrease in muscle size, strength, due to disuse, malnutrition, and/or illness (catabolism)

Contractions can be described in four different ways:

isometric, isotonic concentric, isotonic eccentric and isokinetic.

Isometric

force from muscle is equal to the force from resistance, muscle tightens but doesn’t change length/move so NO movement (ex. plank)

Isotonic Concentric

muscle produces more force than force from resistance, muscle shortens during contraction, ex. bicep curl

Isotonic Eccentric

muscle produces less force than force from resistance (muscle lengthens during contraction) ex. lowering bicep curl

Isokinetic

joint moves at constant speed, ex. stationary bike, treadmills

How does muscles typically function and act?

Muscles usually function in pairs, and act with reciprocal inhibition: their pairings are agonist and antagonist.

Agonist

primary muscle doing the exercise (shortens with tension)

Antagonist

muscle opposing the action of the agonist (lengthening under tension)

Synergist Muscle

assists primary mover (agonist) moving to help complete an action

Fixator Muscle

stabilizes one part of the body to allow another to move more efficiently

Sliding Filament Theory

The sliding filament theory describes the interaction between myofilaments and the molecules responsible for sarcomere or muscle contraction.

What are the factors that play a role in the sliding filament theory?

Calcium, ATP and the proteins actin, myosin, troponin and tropomyosin have specific roles.

Role of calcium for muscle contractions

lets the muscle contraction happen; binds to the troponin which causes the tropomyosin to shift, allowing the actin and myosin to bind

Roles of ATP for muscle contractions

provides energy for the “myosin power stroke”, also required to release the myosin from the actin to allow for relaxation

Role of actin for muscle contractions

thin filament that pulls the thick filament (myosin) along

Role of myosin for muscle contractions

Acts as the motor protein that generates the force for muscle contractions

Role of troponin for muscle contractions

Controls the positioning of tropomyosin (calcium binds to it)

Role of tropomyosin for muscle contractions

Inhibits the muscle contraction by physically blocking the myosin binding sites on the actin filament in a resting muscle

Sliding Filament Order

1. Signal travels down the motor neuron

2. Calcium released from sarcoplasm

3. Actin changes shape

4. Cross bridges form

5. ATP creates a power stroke, shortening actin filament

Involuntary reactions are ______ than voluntary reactions

Faster

How do we generate movement in the body?

Three different classes of levers, both within and outside the human body, work to create movements.

1st Class Lever (E——F—--L/R) or (L/R——F——E)

Fulcrum in the middle & MA can be greater than, less than, or equal to 1 (ex. Neck and Seesaw)

2nd Class Lever (F——L/R——E) or (E——L/R——F)

Load in the middle & MA always greater than 1 (ex. Plank and Wheelbarrow)

3rd Class Lever (F——E——L/R) or (L/R——E——F)

Effort in the middle & MA always less than 1 & Most prominent lever in the human body (ex. Bicep Curl)

MA Equation

Effort Arm / Load Arm OR Load Force / Effort Force

What do levers inside the body do?

Levers inside the body work to create movement. They can be used to project an object that is outside the body or be used as an implement.

What do levers outside the body do?

Levers outside the body can be used to enhance the functionality of movement in a physical activity or to enhance performance.

How are the classes of the lever determined?

The relative positions of the effort, fulcrum and load determine the class, and the mechanical advantage and disadvantage of the lever.

Newton’s 1st Law of Motion (Inertia)

An object at rest/in motion tends to stay at rest/in motion unless acted upon by a force (ex. Tablecloth Trick)

Newton’s 2nd Law of Motion (Acceleration) F=MA

• Acceleration is directly proportional to the net force acting on an object, and inversely proportional to its mass (ex. Ball Roll)

• More force, more acceleration

• More mass, less acceleration

• Force and acceleration have the same direction

• Balanced forces = no acceleration

Newton’s 3rd Law of Motion (Reaction)

For every action, there is an equal and opposite reaction. When two objects interact, they apply forces to each other that are the same in strength but opposite in direction. These forces are called action-reaction forces. (Balloon)

What can be analyzed using Newton’s laws of motion?

Linear Motion - the movement of an object in a straight line, either horizontally or vertically, and is also known as one-dimensional motion

&

Angular Motion - the motion of an object around a fixed point or fixed axis

What terms can be used to describe the motion of an object?

The motion of an object can be described using speed, velocity and acceleration.

How is the resultant motion of an object determined?

The resultant motion of an object is determined by the sum of the forces acting on it.

The following principles relate to applications of Newton’s laws.

Stability, The principle of summoning joint forces, Linear Motion, The principle of impulse direction, Angular Motion

What are factors that affect stability?

factors affecting stability include the height of the centre of mass relative to the supporting surface, the size of the support base, the position of the line of gravity relative to the support base and the mass.

The principle of summoning joint forces

• Bringing together multiple separate forces, efforts, or contributors so they act as one stronger force instead of many weak ones

• the goal is to maximize final velocity of an object, starting from the biggest and going to the smallest

Linear Motion

the greater the impulse applied, the greater the change in linear momentum.

Angular Motion

• describes the rotation of an object around a fixed axis or point, characterized by angular displacement (angle), angular velocity (rate of rotation), and angular acceleration(change velocity)

• this is produced by the application of a force acting at a distance from the centre of mass: an eccentric force.

• Angular momentum is conserved when an athlete or object is free of additional eccentric forces.

Eccentric Force

produces both linear and angular momentum, external force that overcomes a muscle’s internal tension, causing it to lengthen under tension

Angular Momentum

the rotational equivalent of linear momentum, measuring an object's tendency to keep spinning or revolving, defined as the product of its rotational inertia

Impulse Direction

applying a force in the same direction you want an object to move changes the momentum most effectivly

Acceleration

rate at which an object’s speed/velocity changes

Velocity

speed with direction

Speed

how fast somethings moving

Fulcrum

pivot point where a lever rotate/moves

Load

The weight/resistance the lever is trying to move

Effort

bones and muscles that work together to create motion

Mechanical Disadvantage

when a lever requires more effort than the load to move it, but in return, you gain speed and range of motion, allowing the load to move faster and further

Mechanical Advantage (MA)

how much a lever helps you move a load with less effort (smaller=harder)

Tropomyosin

blocks myosin from bonding to actin

Troponin

protein that binds to calcium and moves the calcium bonds to enable muscle contractions

How do myosin and actin interact with each other

myosin binds to actin filament and pulls

Where is calcium released from?

sarcoplasmic reticulum

Calcium Ions

causes the actin to change shape (allowing actin and myosin to connect and muscle to contract)

Sarcomere

actin and myosin are found in it, shortens during a muscle contraction

Myofilament

tiny protein thread (actin-thin or myosin-thick) that slides past others to make a muscle contract

Recruitment Pattern

specific order and way your body turns on different parts of a muscle to perform a movement or lift a weight

Momentum

How hard it is to stop a moving object & Momentum = Mass x Velocity

Impulse

A force applied over a period of time that changes an object’s momentum & Impulse = Force x Time

Muscle Pairings Push-Up Example

• Agonist - The muscle contracts and shortens with tension - Pectoralis Major

• Antagonist - The muscle that lengthens during the contraction- Latissimus Dorsi

• Fixator - Stabilizes the movement - Abdomenal

• Synergist - Muscles that move to help complete the movement/exercise - Deltoid