ESP Unit 3: Resistance training

what is muscle performance

capacity of muscle to do work (force x distance)

what are the main categories of muscle performance

strength

endurance

power

what is muscle strength

maximum force a muscle can generate at a given time

what is muscular pwoer

the ability to exert force quickly

what is muscular endurance

the ability of muscles to sustain repeated contractions or maintain force over an extended period of time

how does muscle length (flexibility) affect muscle performance

it allows greater ROM enhancing the muscle ability to perform optimally across different activities

what is muscle hypertrophy

increase in muscle mass and cross sectional area

what is resistance exercise

physical activity in which dynamic or static muscle contraction is resisted by an outside force applied manually or mechanically

what is resistance training

systematic program of resistance exercises designed to increase an individuals ability to exert or resist force

how does resistance training effect muscle performance

it can increase strength, power, and endurance

what can resistance training do to tendons and ligaments

it can strengthen them

what does resistance training do to injury risk

it decreases the risk of soft tissue injury by increasing the resilience

how can resistance training reduce fall risk

improves strength and control can lead to better balance

what is muscle tension

the force produced when a contracting muscle acts on an object (internal force)

what is a contraction

the process where muscle fibers produce tension through the sliding filament mechanism

what is required for a contraction to create movement

the tension created must exceed the load

what is load

the force exerted on a muscle by an object (external force)

what are the types of contraction

isotonic

isokinetic

ismetric

what are isotonic contractions

muscle length changes while tension is constant

what is isokinetic contraction

there is a constant speed during contraction

what is an isometric contraction

muscles exert force without the muscle length changing

what are myofibrils organized into

sarcomeres

what are the basic contractile units of skeletal muscle

myofibrils

what make up sarcomeres

myosin filaments (thick)

actin filaments (thin)

what is a z line

the walls of a sarcomere indicated the end or start of a sarcomere

what is an A band

the length of the myosin that nerve changeslength

What is the I band

only the actin filament

what is the H zone

only the myosin filament

what changes in the sarcomere occur as myosin and actin filaments slide past each other in a contraction

the H and I zone shrink while the A band remains constant

what is a motor unit

a group of muscle and fibers innervated by a single somatic motor neuron

what occurs to the motor unit when a neuron fires

all the fibers in the unit contract simultaneously

how are the motor units for fine motor muscles organized

they have fewer fibers per unit

how are the motor units for larger muscles that don't require much control organized

there are many fibers per unit

how many types of fibers does each motor unit have

1 fiber type

what starts the excitation contraction coupling and muscle contraction

an action potential in the motor neuron

what does the action potential in a motor neuron trigger

acetylcholine release at the NMJ

what does acetylcholine release at the NMJ cause

depolarization of the muscle fiber and action potential propagation along the sarcolemma and T tubules

when the action potential travels along the sarcolemma and T tubules what happens

voltage gated receptors are stimulated releasing calcium ions from the sarcoplasmic reticulum

where do the calcium ions from the sarcoplasmic reticulum go

they bind to troponin to change tropomyosin exposing the binding sites of actin to allow myosin to attach

what is the sliding filament theory

myosin heads reach out and attach to actin and then pull actin to shorten the muscle

what is the role of ATP in the sliding filament theory

it binds to myosin providing energy to attach, pivot, and detach from actin to facilitate contraction and relaxation

can muscle fiber types change

Yes, they have plasticity

what are type 1 muscle fibers

slow twitch fibers that are slow contracting, have high fatigue resistance, and have small motor neurons

what are type 2a fibers

fast twitch oxidative glycolytic fibers that are moderately fast, have moderate fatigue resistance, and have medium sized motor units

what are type 2x fibers

fast twitch glycolytic fibers that have fast contractions, low fatigue resistance, and have large motor units

how much faster do fast twitch fibers develop tension compared to type 1

2-3 times

how do type 2 fibers have faster twitches

they pump calcium into the sarcoplasmic reticulum more rapidly

what are the biomechanical factors that affect muscle performance

cross sectional size

fiber arrangement and length

fiber type

how does cross section and muscle size effect muscle performance

the larger the muscle diameter the greater tension producing capacity

what muscle architecture is high in force production

short fibers with pennate and multipennate design

what muscle architecture is usually fast but low force producing

long fibers with parallel design

as pennation angle increases what happens to force

it also increases

what fiber distribution leads to slow low force development but is fatigue resistance

high percentage of type 1 fibers

what fiber distribution leads to rapid high force production that fatigues quickly

muscles with a high percentage of type IIA and IIx fibers

what are the mechanical factors affecting muscle performnce

length tension relationship

moment arm

speed of muscle contraction

how does the length tension relationship affect muscle performance

tension is greatest near or at the physiological resting length at time of contraction

how does the moment are between muscle force and axis of rotation effect muscle performance

longer moment arms create more tension

how does motor unit recruitment effect muscle performance

the larger amount and synchronization of motor units firing the more the force production

how does the rate of motor unit firing effect muscle performance

the higher the firing frequency the greater the tension

what is the order of contractions from highest to lowest force production

eccentric

isometric

concentric

how does speed effect tension in concentric contractions

increased speed decreases tension

how does speed effect eccentric contraction tension

increased speed increases tension

what are the biomechanical factors that contribute to muscle performance

mechanical factors

muscle activation

muscle size

muscle architecture

muscle fiber type

what are the psychological factors that effect muscle performance

motivation

fatigue

stress

what is the strongest angle for elbow flexion based on the length tension relationship

between 90 and 130 degrees of elbow extension

what is the sticking point

the point in the range of motion that taxes the muscle maximally

what is the torque joint angle relationship

the greatest torque produced by a muscle is when the muscles force is applied at a 90 degree angle to the joint

is the torque-joint angle relationship unique for each muscle

yes

what is the force velocity relationship

muscle fibers produce less force when they contract faster

why does the force velocity relationship happen

as the muscle fibers contract faster the cross bridges have to detach faster reducing the force output

what is the shape of the force velocity relationship

the velocity decreases in a curvilinear fashion as the load decreases

what is an example of the force velocity relationship

as a heavy weight is lifted more force is required so the weight will move slow compared to a lighter weight that doesn't require as much force moves fast

how does elasticity in the muscle and tendon effect force development

the structures store and release energy

what occurs to a muscle fiber when it undergoes pre-stretch before a contraction

the resultant force is enhanced significantly

what is the stretch shortening cycle

pre activation, stretching, and then shortening the muscle uses the elastic recoil of the muscles and tendon for more powerful action

what is the difference between anatomical cross sectional area and physiological cross sectional area

physiological cross sectional area on the area of the muscle perpendicular to the fibers while anatomical is perpendicular to the muscles longitudinal axis

what is a muscle fiber

a muscle cell

what is the endomysium

connective tissue surrounding individual fibers

what is a fascicle

a bundle of fibers surrounded by connective tissue

what is perimysium

connective tissues surrounding fascicles

what is the epimysium

connective tissue that encloses the entire muscle

what muscle morphology typically generates more power

pennate muscles (uni, Bi, or multi) but they have less shortening capability

what are longitudinal muscles

muscles with long parallel fibers allowing for greater shortening

what occurs when muscle fibers are aligned with the tendon

the force vector is parallel maximizing force transmission

what occurs when fibers are oriented at an angle to the tendon

it allows for more fibers in a muscle area increasing force

what is anthropometry

the measurement of human body proportions

what is an example of anthropometry in squats

people with similar technique, training, and muscle mass but have different femur lengths

the person with longer femurs will experience different forces due to longer moment arms for the quads requiring more force and can lead to different muscle activation patterns

what is torque

force applies by the muscles through a moment arm of a given length at a given angle to the joint

do muscles that attach further from a joint produce more or less torque

more due to a longer moment arm

what is a moment arm

the perpendicular distance between the line of action of muscle force and the joint center

how are muscles designed for high velocity shortening

parallel fibers in a fusiform manner

does muscle size effect force production

yes as muscles grow the moment arms typically lengthen changing the line of pull and increasing the distance from the joint center increasing force production

what activates muscle fibers by forming motor units

alpha motor neurons in the SC ventral horn

what is the sequence of motor unit recruitment

smaller lower threshold units are activated first and larger higher threshold units are progressively recruited as force demand increases

what is sequential motor unit recruitment

recruiting smaller to larger motor units

why are motor units sequentially activated

to allow graded control of muscle force from light to maximum force

what is rate coding

increasing the frequency of impulses to recruit motor units to enhance force output without additional recruitment

what does rate coding allow

smooth and gradual increases in muscle force

why are smaller motor neurons recruited first in contraction

they have higher unput resistance and lower threshold currents making them easier to excite

what creates the neural signal that is sent to muscles

a sum of spiking activities of motor neurons (neural drive)