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EXSS 3850 Test 2
Terms in this set (85)
bio-mechanical force of skeletal muscle?
exert force through muscle contraction
fibers recruited as muscle force requirements increase but are not yet maximal
the formation of cross-bridge attachments between acting and myosin
the idea that governs muscle fiber recruitment
the reason why muscle forces are generally larger than external forces
shorter moment arm
a motor neuron and all the muscle fibers it innervates?
the number of muscle fibers in relation to the number of neurons exciting those fibers
the process of activating a larger or smaller amount of the muscle to control the amount of force
react to the stretch of muscle
the process of increasing the rate of muscle stimulation to increase muscle force
amount of force generated by a muscle at a specific length
length tension relationship
in this way, pole vaulting is similar to muscle function
the bending of the pole store energy in a way similar to stretching a tendon
force production increases with a continued increase in length
length tension relationship for elastic elements
force increases as speed increases
maximized at approximately 1/3 of the maximum shortening velcocity
power/ power-velocity relationship
programmed cell death that occurs in motor neurons
the measure of electrical activity in the muscles
The result of force that causes movement
muscle capable of producing more force due to their fiber alignment
decribe what you would ssee happen in emg readings durning isoketric knee extension
increased slowly over time
exert force through muscle contraction
biomechanical function of skeletal muscle
The three actions of skeletal muscle are
1. Stabilize skeletal joints
2. Mobilize skeletal joints- (muscle concentric function).
3. Stop skeletal motion- (muscle eccentric function).
Muscle forces stiffen joints to strengthen them and enable them to resist external forces and torques. Muscles are contracting
Stabilize skeletal joints
twitch muscles fibers are important in quick, highly forceful movements.
Fast Twitch, high force, high fatigue
Type IIb (fast twitch b)-
twitch muscles fibers are important for events requiring endurance.
Slow twitch, low tension, fatigue resistant
Type I (slow twitch)
twitch muscle fibers are recruited second, as the need for force production begins to increase.
Fast twitch, moderate force, fatigue resitant
Type IIa (fast twitch a)
The process of converting the electrical signal in neuron (the action potential) into the mechanical process of muscle contraction and force production
"muscle contraction," refers to cross bridge formation not shortening of muscle.
ability of sarcomeres, tendons, and total muscle to develop force at different lengths
Length - Tension Relationship
- ability of muscle to develop force at different velocities of shortening (concentric) and lengthening (eccentric)
Force - Velocity Relationship
ability of muscles to develop power (not force) at different velocities of shortening (concentric only)
Power - Velocity Relationship
shortening contraction - muscle shortens while producing force
- muscle torque overcomes (is larger than) external torque and causes movement
- lifting always involves some amount of concentric contractions (e.g. weight lifting, walking up stairs or up hill)
lengthening contraction - muscle lengthens while producing force
- external torque overcomes (is larger than) muscle torque and causes movement
- lowering always involves some amount of eccentric contractions (e.g. weight lifting,walking down stairs)
constant length contraction - muscle stays at constant length while producing force
- muscle torque equals external torque to hold limb stationary (static contraction)
- holding objects always involves isometric contractions (e.g. weight HOLDING)
require more activation per unit force production than lengthening contractions.
Shortening (positive) contractions-
use elastic tissues more effectively while producing force.
Lengthening (negative) contractions
a muscle responsible for producing a specific movement through concentric muscle action
a muscle responsible for opposing the concentric action of the agonist
amount of muscle force perpendicular to bony lever
amount of muscle force parallel to bony lever
Responsible for knee extension, hip extension
responsible for Knee flexion and hip flexion
Force Hooke's law
force * distance
result of a force that causes movement (= Force
displacement or Torque
represents the rate at which work is being done (P=work/time) measured in watts
the energy available to do work
Pole vaulting stores energy in pole and then returns energy to vaulter.
Pole does work on vaulter to lift him above bar.
It is the generation of force through cross-bridge formation, the connection between actin and myosin filaments (more on cross bridges and filaments later).
Muscle contraction IS NOT SHORTENING OF MUSCLE
is the fundamental functional unit in the neuromuscular system
contain fast twitch-glycolytic fibers - produce high force rapidly but fatigue rapidly
Fast twitch - Fatigable (FF)
contain fast twitch-oxidative-glycolytic fibers - produce moderate force at moderate rate and fatigue moderately fast (or slow)
Fast twitch - Fatigue Resistant (FR)
contain slow twitch-oxidative fibers - produce low force at low rate but fatigue slowly
Slow twitch (S)
states that muscle force is produced in a graded fashion so that small-soma motor units are recruited first.
determines precisely how the nervous system controls motor units and entire muscles to produce the exact amount of force required in a particular movement.
is the number of muscle fibers innervated by an alpha motor neuron.
few fibers per neuron - accurate force production
Low innervation ratio
many fibers per neuron - large force production
High innervation ration
Two basic methods to control muscle force
1. Multiple motor unit summation 2. Wave Summation
recruit the necessary amount of motor units to produce the desired force
Multiple Motor Unit Summation
control muscle force by modulating the frequency of action potentials reaching the muscle fibers
higher frequency produces higher force from each motor unit
- Frequency Summation
stretching muscle eccentrically prior to a concentric contraction - increases force production in concentric contraction
Stretch Shortening Cycle
What is Force enhancing process?
1. Mechanical 2. Neurologic
stretching elastic tissues stores energy in these tissues for use in concentric contraction
stretching muscle spindles enhances the alpha-motor neuron drive to the muscle to increase the concentric force
an encapsulated sensory receptor that lies parallel to muscle fibers and responds to stretch of the muscle
- Encapsulated sensory organs located within muscle tendons
Concentrated in aponeurosis - area connecting muscle fibers and tendons
Sense small changes in tension Inhibits contracting (agonist) muscles and excites antagonist muscles to prevent injury (poly-synaptic reflex - more than one neuronal pathway)
Golgi Tendon Organs
Measures muscle activity
measures performances of different muscle groups, what I was in in therapy
_____ neurons carry impulses from the muscle to the CNS, while _____ neurons complete the loop by carrying impulses from the CNS to the muscle.
The action potential is a propagated impulse, meaning that the amplitude of the impulse _____ as it travels down the axon to the motor end plate.
remains the same
Gluteus maximus, biceps brachii, orbicularis oculi
Order the following muscles from most muscle fibers per motor unit to least: biceps brachii, gluteus maximus, orbicularis oculi.
Following the size principle, in what order are motor units recruited
I, IIa, IIb
How many muscle fibers can be controlled by one motor unit?
In what order are motor units deactivated?
The reverse order as activation
Why do some people see significant strength gains after only four weeks of a strength training program?
Better coordination of motor unit activation
Which is a proprioceptor?
muscle spindles, and golgi tendon
In the three-component model of muscle, which component most closely corresponds to the tendon
Series elastic component
Which type of athlete is most likely to have the highest concentration of Type I muscle fibers?
Which is NOT one of the four properties of skeletal muscle tissue?
In the sliding filament theory, what slides past one another during contraction?
Actin and myosin
In the three-component model of muscle, which component most closely corresponds to the connective tissue sheaths?
Parallel elastic component
During which movement is the greatest muscle force possible?
Lowering a weight
Which muscle fiber type is only oxidative?
Holding a box while waiting for your friend to open a door is an example of what type of contraction?
Which type of exercise is generally more functional?
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