• internal motors of human body responsible for all movements of skeletal system
• only have the ability to pull
• must cross a joint to create motion
• can shorten up to 70% of resting length

• 3 components
CC contractile component
SEC series elastic component
PEC parallel elastic component

SEC
Whole
Muscle
CC
PEC
•
Contractile Component (CC)
–active shortening of muscle through actin-myosin structures
•
Parallel Elastic Component (PEC)
–parallel to the contractile element of the muscle
–the connective tissue network residing in the perimysium, epimysium and other connective tissues which surround the muscle fibers
•
Series Elastic Component (SEC)
–in series with the contractile component
–resides in the cross-bridges between the actin and myosin filaments and the tendons

CC
Tissue
SEC
PEC
Both SEC & PEC behave like springs when acting quickly but they also have viscous nature
If muscle is statically stretched it will progressively stretch over time and will slowly return to resting length when the stretching force is removed.

Whole
Muscle
• a quick stretch followed by concentric action in the muscle
• Store energy in elastic structures
• Recover energy during concentric phase to produce more force than concentric muscle action alone
• examples
– vertical jump: counter-movement vs. no counter-movement
– plyometrics
SEC
CC
PEC

• irritability - responds to stimulation by a chemical neurotransmitter (ACh)
• contractibility - ability to shorten (50-70%), usually limited by joint range of motion
• distensiblity - ability to stretch or lengthen, corresponds to stretching of the perimysium, epimysium and fascia
• elasticity - ability to return to normal state
(after lengthening)
Tissue

“Bundle-within-a-Bundle”
Tissue

Tissue
Sliding Filament Theory
1) Myosin filaments form a cross-bridge to actin
2) Myosin pulls actin actin
3) x-bridge releases myosin
4) Myosin ready for another x-bridge formation

Tissue
• the number of sarcomeres in series or in parallel will help determine the properties of a muscle
3 sarcomeres in series
(high velocity/ROM orientation)
3 sarcomeres in parallel
(high force orientation)

Sarcomere organization example:
Note that the values are not representative of actual sarcomeres.
Force
ROM
1 sarcomere
1 N
1 cm
3 sarcomeres in series
3 sarcomeres in parallel
1 N 3 N
3 cm
Time 1 sec 1 sec
Velocity 1 cm/sec 3 cm/sec
1 cm
1 sec
1 cm/sec

• the longer the tendon-to-tendon length the greater number of sarcomeres in series
• the greater the physiological cross-sectional area (PCSA) the greater number of sarcomeres in parallel sarcomeres in series sarcomeres in parallel

• fibers run longitudinally
• generally fibers do not extend the entire length of muscle

• tendon runs parallel to the long axis of the muscle, fibers run diagonally to axis (short fibers)
Tissue

Fusiform vs. Pennate
• fusiform
– advantage : sarcomeres are in series so maximal velocity and ROM are increased
– disadvantage : relatively low # of parallel sarcomeres so the force capability is low
• pennate
– advantage : increase # of sarcomeres in parallel, so increased PCSA and increased force capability
– disadvantage : decreased ROM and velocity of shortening
Tissue

Tissue
• all fibers within a motor unit are of the same type
• within a muscle there is a mixture of fiber types
• fiber type may change with training
• recruitment is ordered
– type I recruited 1st (lowest threshold)
– type IIa recruited second
– type IIb recruited last (highest threshold)

Tissue

Tissue
Type I
Shortening
Speed slow
Energy System oxidative
Size
Force
Production
Aerobic
Capacity
Anaerobic
Capacity
Fatigability small low high low low
Type IIa fast oxidative, glycolytic large high medium medium medium
Type IIb fast glycolytic large high low high high

l
0
- neither contracted nor stretched i o n
T e n s
Length l
0
Tissue

Tissue
l
0
- neither contracted nor stretched
T physiological limit combined active l
0 passive
L

Tissue v < 0
(eccentric) v=0
(isometric) v > 0
(concentric) velocity of contraction

F
Tissue
Power (F*v) v
30% v max

Muscle Attachment - Tendons
Whole
Muscle
Fusion b/w epimysium and periosteum
Tendon fused with fascia

attachment can be directly to the bone or indirectly via a tendon or aponeurosis
Whole
Muscle
Origin -- generally proximal, fleshy attachment to the stationary bone
Insertion -- generally distal, tendinous and attached to mobile bone defining origin or insertion relative to action of bone is difficult e.g. hip flexors in leg raise v. sit-up

Whole
Muscle
• produce movement - when the muscle is stimulated it shortens and results in movement of the bones
• maintain postures and positions - prevents motion when posture needs to be maintained
• stabilize joints - muscles crossing a joint can pull the bones toward each other and contribute to the stability of the joint

Whole
Muscle
• generally have more than
1 muscle causing same motion at a joint
• together these muscles are referred to as a functional group
• e.g. elbow flexors -biceps brachii, brachialis, and brachioradialis - all flex elbow

Whole
Muscle
• prime mover the muscles primarily responsible for the movement
• assistant mover muscles used only when more force is required
• agonist - muscles responsible for the movement
• antagonist - performs movement opposite of agonist
• stabilizer - active in one segment to stabilize a bone so that a movement in an adjacent segment can occur
• neutralizer - active to eliminate an undesired joint action of another muscle

Whole
SHOULDER ABDUCTION
Muscle agonist: deltoid antagonist: latissimus dorsi stabilizer: trapezius holds the shoulder girdle in place so the deltoid can pull the humerus up neutralizer: teres minor if latissimus dorsi is active then the shoulder will tend to internally rotate, so the teres minor can be used to counteract this via its ability to externally rotate the shoulder

• isometric action
– no change in fiber length
• concentric action
– shortening of fibers to cause movement at a jt
• eccentric action
– lengthening of fibers to control or resist a movement
Whole
Muscle

Whole
Muscle

Concentric action:
• work against gravity to raise the body or objects
• speed up body segments or objects
Whole
Muscle
Eccentric action:
• work with gravity to lower the body or objects
• slow down body segments or objects concentric eccentric

•push-up
 up - concentric action of elbow extensors
 down - eccentric action of elbow extensors
•catching a baseball
 eccentric action of elbow extensors
•throwing a baseball
 concentric action of elbow extensors
•pull-up
 up - concentric action of elbow flexors
 down - eccentric action of elbow flexors
Whole
Muscle

Whole
Muscle
The countermovement elicits an increase in force production the increase in force production is 30% neural and 70% elastic contribution
Greatest return of energy is achieved using a “dropstop-pop” action with only an 8”-12” drop

Whole
Muscle
• uniarticular or monoarticular - the muscle crosses 1 joint, so it affects motion at only 1 joint
• biarticular or multiarticular - the muscle crosses 2 (bi) or more (multi) joints, so it can produce motion across multiple joints

Whole
Muscle
• can reduce the contraction velocity
• can transfer energy between segments
• can reduce the work required of single-joint muscles
• more susceptible to injury

Whole
Muscle
• a disadvantage of 2-joint muscles
– active insufficiency - cannot actively shorten to produce full ROM at both joints simultaneously
– passive insufficiency - cannot be stretched to allow full ROM at both joints simultaneously

Whole
Muscle
• squeeze the index finger of another student
• move the wrist from extreme hyperextension to full flexion
• What happens to the grip strength throughout the ROM?
• WHY?

Whole
Muscle
• flexibility - the state of muscle’s length which restricts or allows freedom of joint movement
• endurance - the ability of muscles to exert force repeatedly or constantly

Whole
Muscle
• strength - the maximum force that can be achieved by muscular tension
• power - the rate at which physical work is done or the force created by a muscle multiplied by its contraction velocity

Whole
Muscle
• measure absolute force in a single muscle preparation
• in real life most common estimate of muscle strength is maximum torque generated by a given muscle group

Whole
Muscle
Training focuses on developing larger x-sectional area
AND developing more tension per unit of x-sectional area
Magnitude of strength gains dependent on from an “untrained state”
1st 12 weeks see improvement on the neural side via improved innervation
1) genetic predisposition
2) training specificity
3) intensity
4) rest
5) volume later see increase in x-sectional area

Isometric
Exercise
Isotonic
Exercise
Whole
Muscle
Isokinetic
Exercise
Training Modalities
Close-Linked
Exercises
Variable Resistance
Exercise

Muscle Injury
Greatest Risk a) 2-joint muscles b) muscles that limit ROM c) muscles used eccentrically
Whole
Muscle
Individuals at risk a) fatigued state b) not warmed-up c) new exercise/task d) compensation
Soreness v. Damage
damage believed to be in fiber
soreness due to connective tissue

Whole
Muscle
• rotary component
– causes motion
– perpendicular to the rotating segment
• stabilizing or dislocating component
– parallel to rotating segment
– stabilizing is toward joint
– dislocating is away from joint

Whole
Muscle
• components depend on the joint angle small rotary large stabilizing large rotary small stabilizing medium rotary medium dislocating

• angular motion occurs at a joint so technically torque causes motion
• torque is developed because the point of application of the force produced by muscle is some distance away from the joint’s axis of rotation muscle force (F m
)
Whole
Muscle muscle torque (T m
) distance between pt of application and joint axis
(d m
)

Whole
Muscle
400 N
F m
F m
60 o
0.03 m
T m
= F * m d
Torque = 400 N * 0.03 m becasue F m is not to the forearm!!!
perpendicular
F m
To solve problem we must resolve the vector F m components which are into perpendicular (F m
) and parallel (F m
) to the forearm.

Whole
Muscle
400 N
F m
F m
F m F m
F m
F m
0.03 m
Only the perpendicular component will create a torque about the elbow joint so only need to calculate this.

Whole
Muscle
T = 345 N * 0.03 m = 10.4 Nm
400 N
0.03 m Angle of Pull Affects Torque
400 N
T = 200 N * 0.03 m = 6 Nm
0.03 m
F
R
= 200 N

Whole
Muscle
T = 345 N * 0.03 m = 10.4 Nm
400 N
0.03 m
Size of Muscle Force Affects Torque
600 N
F
R
= 345 N
T = 520 N * 0.03 m = 15.6 Nm
0.03 m
F
R
= 520 N

Whole
Muscle
T = 345 N * 0.03 m = 10.4 Nm
400 N
0.03 m
T = 345 N * 0.1 m = 34.5 Nm
Moment Arm Affects Torque
400 N
F
R
= 345 N
0.1 m

Whole
Muscle
400 N
F m
F m
F m F m
F m
60 o
F m
60 o
0.03 m
NOTE: The torque created by the muscle depends on
1) the size of the muscle force
2) the angle at which the muscle pulls
3) the distance that the muscle attaches away from joint axis

Whole
Muscle
Changing any of these 3 factors will change the torque:
1) muscle force - changed by increased neural stimulation
2) d can’t change voluntarily but use of other muscles in same functional muscle group gives a different d
3) q
- this changes throughout the ROM

Whole
Muscle
Muscle Force
1) level of stimulation
2) muscle fiber type
3) PCSA
4) velocity of shortening
5) muscle length
Angle of pull
Moment arm