Strength/Conditioning- Exam 1

Chapters 1-3

What systems are important and Why?

• Skeletal- joints and ligaments

• Muscular- sliding filament theory

• Nervous system- all or non principle, muscle spindles, GTO’s

• Cardiovascular- pathway, conduction, transportation

• Respiratory- pathway, gas exchange, pressure gradient

Skeletal system

• Composed of 206 bones in the adult body

• provides leverage, support, and protection

• pulled on by muscles to allow the body to push or pull against external objects

Axial vs. Appendicular Skeleton

• Axial: consists of skull, vertebral column, ribs, and sternum

• Appendicular: consists of shoulder girdle; bones of the arms, wrists, hands, and pelvic girdle; and bones of the legs, ankles, and feet

  • Appendicular=appendages

Types of Joints

• Joint: junction of bones

• Fibrous: allow virtually no movement

  • sutures of the skull

• Cartilaginous: allow limited movement

  • intervertebral

• Synovial: allows considerable movement

  • elbows and knees

Types of Joints (Axial)

• Uniaxial: operates as a hinge, rotates about one axis

• biaxial: operates in two perpendicular axes

• multiaxial: allow movement in all three axes

Vertebral Column

Vertebral bones separated by flexible disks that allow for movement

• Cervical vertebrae (neck region): 7

• Thoracic vertebrae (Upper back): 12

• Lumbar Vertebrae: (lower back): 5

• Sacral vertebrae (make up rear of pelvis): 5

• Coccygeal vertebrae (from vestigial tail extending down from the pelvis): 3-5

Muscular System

• Schematic Drawing of a muscle

  • epimysium (outer layer)

  • Perimysium (surrounding each fasciculus, or group of fibers)

  • endomysium (surrounding individual fibers)

Myosin and Actin

• Myosin and actin protein filaments in muscle

• the arrangement of myosin (thick) and actin (thin) filaments gives skeletal muscle its striated appearance

Key Point

• The discharge of an action potential from a motor nerve signals the release of calcium from the sarcoplasmic reticulum into the myofibril, causing tension development in muscle

Muscular system- Sliding Filament Theory

• states that the actin filaments at each end of the sarcomere slide inward on myosin filaments, pulling the Z-lines toward the center of the sarcomere and thus shortening the muscle fiber

Contraction of a Myofibril

•a) In stretched muscle the I-bands and H-zone are elongated, and there is low force potential due to reduced crossbridge–actin alignment.

•b) When muscle contracts (here partially), the
I-bands and H-zone are shortened.

•(c) With completely contracted muscle, there is low force potential due to reduced crossbridge–actin alignment.

Sliding filament (in depth)

-Resting phase

-Excitation- contraction coupling phase

• calcium release—>binds to troponin—>moves tropomyosin

-Contraction phase

• Myosin filament attaches to actin b/c the tropomyosin is moved

  • power stroke- use of ATP and production of ADP

-Recharge phase

• continuation of contraction

-Relaxation phase

• Motor nerve stops sending signal and calcium pumped out of muscle

What dictates the force production of a muscle?

The number of cross-bridges that are formed between actin and myosin at any instant in time

What is necessary for cross-bridge cycling with actin and myosin filaments?

Calcium and ATP

Activation of Muscles

• Arrival of the action potential at the nerve terminal causes the release of acetylcholine.

• Once a sufficient amount of acetylcholine is released, an action potential is generated across the sarcolemma, and the fiber contracts

Motor Unit Action Potential

acetylcholine crosses sarcolemma= fiber contraction

Motor Unit

• A motor neuron and the muscle fibers it innervates

• There are typically several muscle fibers in a single motor unit

Activation of muscles

• The extent of control of a muscle depends on the number of muscle fibers within each motor unit

  • Muscles that function with great precision may have as few as one muscle fiber per motor neuron

    • fingers

  • Muscles that require less precision may have several hundred fibers served by one motor neuron

    • thigh

All-or-none-principle

All of the muscle fibers in the motor unit contract and develop force at the same time

Muscle Fiber Types

• Type I (slow-twitch)

• Type IIa (fast-twitch)

• Type IIx (fast-twitch)

Motor Units Key Point

Motor units are composed of muscle fibers with specific morphological and physiological characteristics that determine their functional capacity

Motor Unit Recruitment Patterns During Exercise

The force output of a muscle can be varied through change in the frequency of activation of individual motor units or change in the number of activated motor units

Proprioceptors

Specialized sensory receptors that provide the central nervous system with information needed to maintain muscle tone and perform complex coordinated movements

Golgi Tendon Organs (GTO)

Golgi tendon organs are proprioceptors located in tendons near the myotendinous junction

• When an extremely heavy load is placed on the muscle, discharge of GTO occurs

• The sensory neuron of the GTO activates an inhibitory interneuron in the spinal cord, which in turn synapses with and inhibits a motor neuron serving the same muscle

How can athletes improve force production?

• incorporate phases of training that use heavier loads in order to optimize neural recruitment

• Increase the cross-sectional area of muscles involved in the desired activity

• perform multi-muscle, multipoint exercises that can be done with more explosive actions to optimize fast-twitch muscle recruitment

  • Big bang for your buck exercises

Heart

• The heart is a muscular organ made up of two separate pumps

  • The right ventricle pumps blood to the lungs

  • The left ventricle pumps blood to the rest of the body

Valves

• Tricuspid valve and mitral (bicuspid)

• Aortic valve and pulmonary valve

• valves open and close passively depending on the pressure gradient

• Blood flow through heart

  • right atrium- tricuspid valve- right ventricle- pulmonary valve- lungs

  • Left atrium- mitral valve- left ventricle- aortic valve- body

• Conduction system

  • controls the mechanical contraction of the heart

• Tricuspid= right

• aortic= left

• Bicuspid= left

• pulmonary= right

SA Node

Pacemaker of the heart

Rhythmicity and conduction properties of myocardium

• Influenced by cardiovascular center of medulla

• signals transmitted through sympathetic and parasympathetic nervous systems

• bradycardia (<60 beats/min)

• Tachycardia (>100 beats/min)

Sympathetic

fight or flight

Parasympathetic

rest and digest

Electrocardiogram

• Record at the surface of the body

• A graphic representation of the electrical activity of the heart

Blood vessels

• Blood vessels operate in a closed-circuit system

• The arterial system carries blood away from the heart

• The venous system returns blood toward the heart

Blood Vessel Components

• Arteries

• Capillaries

• Veins

Blood

• Hemoglobin transports oxygen and serves as an acid-base buffer

• Red blood cells facilitate carbon dioxide removal

Exchange of respiratory gases

The primary function of the respiratory system is the basic exchange of oxygen and carbon dioxide

Exchange of air

the amount and movement of air and expired gases in and out of the lungs are controlled by expansion and recoil of the lungs

Alveolar pressure

• pressure gradient inside the alveoli when the glottis is open and no air is flowing into or out of the lungs

• To cause inward flow of air during inspiration, the pressure in the alveoli must fall to a value slightly below atmospheric pressure

• During expiration, alveolar pressure must rise above atmospheric pressure

Exchange of respiratory gases

The process of diffusion is a simple random motion of molecules moving in opposite directions through the alveolar capillary membrane

Biomechanics

the mechanisms through which components interact to create movement

Agonist

the muscle most directly involved in bringing about a movement

• prime mover

antagonist

muscle that can slow down or stop the movement

synergist

a muscle that assists indirectly in a movement

Skeletal musculature

• system of muscles enables the skeleton to move

• origin= proximal (toward the center of the body) attachment

• Insertion= distal (away from the center of the body) attachment

Levers of the musculoskeletal system

• Many muscles in the body do not act through levers

• Body movements directly involved in sport and exercise primarily act through the bony levers of the skeleton

Lever

rigid or semigrid body that, when subjected to a force whose line of action does not pass through its pivot point, exerts force on any object impeding its tendency to rotate

FA

force applied to the lever

M_AF

moment arm of the applied force

F_R

force resisting the lever’s rotation

M_RF

moment arm of the resistive force

• the lever applies a force on the object equal in magnitude to but opposite in direction from F_R

First Class Lever

A lever for which the muscle force and resistive force act on opposite sides of the fulcrum

Mechanical Advantage

Less than 1.0 is a disadvantage

Second Class Lever

Due to the muscle’s mechanical advantage, the required muscle force is smaller than the resistive force

Third class lever

Muscle force has to be greater than the resistive force

Mechanical Advantage

The ratio of the moment arm through which an applied force acts to that through which a resistive force acts

The patella and mechanical advantages

(a) Patella increases the mechanical advantage of the quadriceps muscle group by maintaining the quadriceps tendon’s distance from the knee’s axis of rotation

(b) Absence of the patella allows the tendon to fall closer to the knee’s center of rotation, shortening the moment arm through which the muscle force acts and thereby reducing the muscle’s mechanical advantage

Do most skeletal muscles operate at a considerable mechanical disadvantage or advantage?

Mechanical disadvantage

Variations in Tendon insertion

• Tendon insertion farther from the joint center results in the ability to lift heavier weights

Anatomical planes

• The sagittal planes slices body into right and left sections

• frontal plane slices body into front-back sections

• Transverse plane slices the body into upper-lower sections

Strength

the capacity to exert force at any given speed

Acceleration

the change in velocity per unit time

force= mass X acceleration

Power

• outside of the scientific realm, power is loosely defined as “explosive strength”

• also defined as the time rate of doing work

• Power= work/time

Work

• Product of force exerted on an object and the distance the object moves in the direction the force is exerted

• Work= Force X Displacement

Negative power

• work performed on, rather than by, a muscle

• occurs during eccentric muscle actions

strength and power both have the ability to do what?

exert force at a given velocity

Recruitment

the amount of motor units involved in a muscle contraction

Rate of coding

the rate at which motor units are fired

Muscle forces are greater when

• motor units involved

• the motor units are greater in size

• the motor units fire faster

• all or non principle

Muscle contraction

the force a muscle can exert is related to its cross-sectional area rather than its volume

Pennate Muscles

muscle fibers that align obliquely with the tendon creates feather-like arrangement

Angle of Pennation

The angle between the muscle fibers and an imaginary line between the muscles origin and insertion

Muscles with Pennation

• Have more sarcomeres

• Able to generate more force

Muscle Length

• Muscle is strongest at its resting length

• Strength is dependent on how many cross-bridges can be formed

• When a muscle is stretched actin and myosin are far apart and cannot create cross-bridges

• When a muscle is contracted actin and myosin overlap and can’t form as many cross-bridges

Torque

The variable of force needed for rotation

Where is a joint the strongest?

At lowest joint angle

As muscle contraction velocity increases

the force created decreases

Concentric muscle action

contractile force is greater than resistive force causing muscle to shorten

Eccentric Muscle Action

Muscle lengthens, keeps weight from going downward from gravitational pull

Isometric muscle action

muscle length does not changes because the forces are equal

• no movement of joint

Strength to mass formula

• strength/mass

• Higher strength, lower mass= greater speed/acceleration

• as mass increases, strength proportionally increases

• For combat sports like wrestling an athlete will try to find an ideal minimum weight for their bodies and try to get as strong as possible at that weight

Body Size

• Smaller muscle gets stronger and faster

• as body size increases, body mass increases more rapidly than muscle strength

Gravity

• Applications to resistance training:

  • When the weight is horizontally closer to the joint, it exerts less resistive torque

  • When the weight is horizontally farther from a joint, it exerts more resistive torque

What can exercise technique affect?

The resistive torque pattern during an exercise and can shift stress among muscle groups

Inertia

• Though the force of gravity acts only downward, inertial force can act in any direction

• However, upward or lateral acceleration of the weight requires additional force

Friction

• Friction is the resistive force encountered when one attempts to move an object while it is pressed against another object

Fluid resistance

Fluid resistance is the resistive force encountered by an object moving through a fluid (liquid or gas), or by a fluid moving past or around an object or through an opening

Elasticity

The more an elastic component is stretched, the greater the resistance

Concerns in resistance training

Back:

• Back injury

  • the lower back is particularly vulnerable

  • resistance training exercises should generally be performed with the lower back in a moderately arched position

Valsalva Maneuver

No air escapes from lungs, muscles of torso contract creating rigid compartments or liquid and air

Shoulders

• The shoulder is prone to injury during weight training because of its and the forces to which it is subjected

• warm up with relatively light weights

• follow a program that exercises the shoulders in a balanced way

• exercise at a controlled speed

Knees

The knee is prone to injury because of its location between two long levers

Elbows and wrists

• The primary concern involves overhead lifts

• The most common source of injury to these areas is from overhead sports such as throwing events or the tennis serve

Bioenergetics

The flow of energy in a biological system

Catabolism

The breakdown of large molecules into smaller molecules, associated with the release of energy

Anabolism

The synthesis of larger molecules from smaller molecules

Exergonic reactions

Energy-releasing reactions that are genetically catabolic

endergonic reactions

requires energy and include anabolic processes and the contraction of muscle

Metabolism

The total of all catabolic or exergonic and anabolic or endergonic reactions in a biological system

Adenosine Triphosphate (ATP)

Allows the transfer of energy from exergonic to endergonic reactions

Three basic energy systems that exist in muscle cells to replenish ATP

• Phosphagen system

• Glycolysis

• Oxidative System