Chapter 6 Learnsmart Biomechanics
Identify the true statements about the muscle force-velocity relationship. (Check all that apply.)
-It suggests that the maximal force that a muscle can develop is governed by the velocity of the muscle's shortening or lengthening. -It suggests that the stronger the muscle is, the greater the magnitude of maximum isometric tension.
Identify the characteristics of muscle fatigue. (Check all that apply.)
-prolonged relaxation of motor units between recruitment -reduction in muscle force production capability
Identify the factors that influence a muscle's moment arm for generating maximum torque at a joint. (Check all that apply.)
-the distance between a muscle's anatomical attachment to the bone and the axis of rotation at the joint center - the angle of a muscle's attachment to bone
Calculate the angle of insertion on the radius of a joint (α) when the muscle tension (Fm) is 500 N and the torque produced at the joint (Tm) is 25 N. Assume that the muscle attachment to the radius is 10 cm from the center of rotation at the joint.
30°
Calculate the muscle tension (Fm) at a joint when the angle of insertion on the radius of the joint (α) is 45° and the torque produced at the joint (Tm) is 18 N. Assume that the muscle attachment to the radius is 6 cm from the center of rotation at the joint.
424.27 N
Given that the tension-generating capability of muscle tissue is 90 N/cm2, calculate the tension that may be developed in muscles with the cross-sectional area of 5 cm2.
450 N
Calculate the force exerted by the tendon of a pennate muscle when the tension in the fibers (Ffibers) is 70 N and the angle of pennation (α) is 45°.
49.49 N
Given that the tension-generating capability of muscle tissue is 90 N/cm2, calculate the cross-sectional area of a muscle if the tension developed in that muscle is 720 N.
8 cm2
Samantha and Vicky are performing strength training exercises. The load Vicky lifts develops 180 N of tension in the muscle fibers (Ff), while the load Samantha lifts develops 150 N of tension in the muscle fibers (Ff). Assuming that the angle of pennation (α) of the muscle fibers for both girls is 60°, calculate the amount of force exerted by the tendons of the pennate muscles (Ft) of Vicky and Samantha, respectively.
90 N; 75 N
At what angle should a muscle be oriented to the bone for the production of the greatest amount of torque at a joint?
90°
______ contraction occurs when muscular tension produces a torque larger than the resistive torque at a joint.
Concentric
_____ consist of hematomas within the muscle tissue.
Contusions
_____, or muscle bruises, are caused by compressive forces sustained during impacts.
Contusions
______, arising 24-72 hours after participation in a strenuous bout of exercise, is characterized by pain, swelling, and the same kinds of histological changes that accompany acute inflammation.
Delayed-onset muscle soreness
True or false: Increased human body temperature results in decreased muscular strength.
False
Identify an example of active insufficiency with the function of two-joint muscles.
Finger flexors cannot produce as tight a fist when the wrist is in flexion as when it is in a neutral position.
Identify an accurate statement about the muscle force-velocity relationship.
It does not imply that it is impossible to move a heavy resistance at a fast speed.
Identify a true statement about eccentric strength training.
It involves the use of resistances that are greater than the athlete's maximum isometric force generation capability.
Identify an accurate statement about the tension in a twitch fiber following the stimulus of a single nerve impulse.
It rises to a peak value in less than 100 msec and then immediately declines.
A _____ ______ refers to a single motor neuron and all muscle fibers it innervates.
Motor Unit
______ is defined as reduced capacity of muscle fibers to produce force, even in the presence of motor neuron excitation.
Muscle fatigue
______ is a muscle's ability to exert tension over time.
Muscular endurance
Tetanus
Prolonged exposure causes fatigue leading to gradual decline in the level of tension produced.
Muscles that act to stabilize a body part against a particular force assume the role of ___________
Stabilizer
______ refers to a pattern of eccentric contraction of muscles followed immediately by concentric contraction.
Stretch-shortening cycle
Summation
Tension is progressively elevated until a maximum value for a fiber is reached.
______ is a muscle property enabling tension development by stimulated muscle fibers.
The contractile component
parallel fiber arrangement
The fibers are oriented largely in parallel with the longitudinal axis of a muscle.
pennate fiber arrangement
The fibers lie at an angle to a muscle's longitudinal axis.
Which of the following is an example of passive insufficiency?
The restriction of range of motion when the finger flexors are maximally stretched with both the wrist and the fingers in full extension
Which of the following is true of motor units?
There is only one motor end plate per muscle fiber.
Identify a true statement about slow-twitch motor units.
They always produce tension first, whether the resulting movement is slow or fast.
Identify a mathematical formula that defines net torque generated in a joint.
Tm = Fm × dι
Skeletal motor units in mammals that respond to a single stimulus by developing tension in a twitch-like fashion are called _______ _______ cells
Twitch - type
second-degree strains
a partial tear in the muscle tissue
Elevation in human body temperature causes ______.
a shift in the force-velocity curve for muscles
contractile component
active contribution
A condition occurring when a two-joint muscle cannot shorten enough to cause a full range of motion at both joints it crosses at the same time is referred to as ______.
active insufficiency
When a muscle contracts and causes movement of a body segment at a joint, it is acting as an ______, or mover.
agonist
A muscle that acts to slow or stop the movement of a body segment at a joint plays the role of a(n) ______.
antagonist
Anatomically, for the production of the greatest amount of torque at a joint, the muscle must ______.
be attached as far from the joint center as possible
When assessed through the measurement of maximum torque generated by a muscle group at a joint, muscular strength is a function of the ______.
collective force-generating capability of that muscle group
Injury or excessive muscular exertion causing hemorrhage or edema within a muscle compartment results in the ________ syndrome
compartment
A contraction involving the shortening of a muscle is known as a ______ contraction.
concentric
In the context of the force-velocity relationship for muscle tissue, when the resistance (force) is negligible, muscle contracts with maximal velocity. As the load progressively increases, ______ contraction velocity slows to zero at isometric maximum. As the load increases further, the muscle lengthens ______.
concentric; eccentrically
The electromechanical delay observed when a muscle is stimulated is needed for the ______.
contractile component of the muscle to stretch the series elastic component
The ability to ______ is unique to muscle tissue.
develop tension
Antagonists oppose the actions of agonists by ______.
developing eccentric tension the same time that agonists are causing movement
internal forces
due to tension in other muscles
external forces
due to the weight of an object being lifted
A contraction involving lengthening of a muscle is described as a(n) ______ contraction.
eccentric
A(n) ______ contraction occurs when an opposing joint torque exceeds that produced by tension in a muscle.
eccentric
Identify an application of the stretch-shortening cycle (SSC).
effective development of concentric muscular force in sport activities
The time between the arrival of neural stimulus and tension development by the muscle is referred to as ______.
electromechanical delay
The technique of recording myoelectric activity is known as _____.
electromyograpghy
True or false: Slow twitch (ST) fibers usually fatigue more quickly than do fast twitch (FT) fibers.
false
One of muscle's characteristic properties, ______, is the ability to respond to a stimulus.
irritability
A(n) ______ contraction describes a contraction involving no change in muscle length.
isometric
When an opposing torque at a joint crossed by a muscle is equal to a torque produced by the muscle (with zero net torque present), ______ contraction occurs.
isometric
The maximum amount of force a muscle can produce under normal static conditions is called the ______.
isometric maximum
series elastic component
it is derived from from the tendons
parallel elastic component
it is derived from the muscle membranes
Training for muscular endurance typically involves ______.
large numbers of repetitions against relatively light resistance
muscle shortening
less muscle tension development capability
muscle stretching
maximum muscle tension development capability
In order to evaluate the muscle strength of a muscle group at a joint, the ______ is measured.
maximum torque generated by the muscle group
sarcolemma
membrane surrounding a muscle fiber
mild strains
minimal structural damage to the muscle tissue
A _______ ________ refers to a single motor neuron and all muscle fibers it innervates.
motor unit
The product of muscular force and the velocity of muscle shortening is known as ______.
muscular power
The sarcoplasm contains numerous threadlike ______ that are aligned parallel to one another.
myofibrils
Electromyography is used to study ______ function.
neuromuscular
Those muscles which prevent unwanted accessory actions produced by agonists play the role of ______.
neutralizers
Skeletal motor units of the tonic type are found in the ______.
oculomotor apparatus
serial and parallel elastic components
passive contribution
For most people, two-joint and multijoint muscles cannot stretch to the extent required for full range of motion in the opposite direction at all joints crossed. This problem is referred to as ______.
passive insufficiency
surface electrodes
pick up global myoelectric activity
fine-wire electrodes
pick up localized myoelectric activity
Muscular power is more generally defined as the ______.
rate of torque production at a joint
pennate fiber arrangement
rotation about their tendon attachment or attachments
The absence of pressure release from a muscle compartment results in ______.
severe damage to the neural and vascular structures in the compartment
third-degree strains
severe tearing of the muscle
parallel fiber arrangement
shortening of muscles
When does muscle soreness occur?
some period of time following unaccustomed exercise
sarcoplasm
specialized cytoplasm of a muscle fiber
During the elbow flexion phase of a forearm curl, which of the following acts as a primary agonist?
the brachialis
slow twitch type
the fibers of motor units that contract to reach maximum tension gradually after being stimulated
fast twitch type
the fibers of motor units that contract to reach maximum tension quickly after being stimulated
parallel fiber arrangement
the sartorius, rectus abdominis, and biceps brachii muscles
pennate fiber arrangement
the tibialis posterior, rectus femoris, and deltoid muscles
muscle fiber
threadlike cells of a muscle
Skeletal motor units of the ______ type require more than a single stimulus before the initial development of tension.
tonic
The process of electromyography involves the use of ______, which are devices that detect signals.
transducers
True or false: In case a muscle causes both flexion and abduction at a joint but only flexion is desired, the action of a neutralizer causing adduction can eliminate the unwanted abduction.
true
The net torque generated at a joint is the ______.
vector sum of the muscle torque and the resistive torque
The ______ property of a muscle refers to its ability to stretch or shorten over time.
viscoelastic
A muscle is enabled to stretch and recoil in a time-dependent fashion due to the ______.
viscous property of its series and parallel elastic components
tetanus
when a fiber is repetitively activated so that its maximum tension level is maintained for a time
summation
when rapid, successive impulses activate a fiber already in tension
