1. Muscle
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

2. Muscle-Tendon Model 3 components CC contractile component SEC
series elastic component CC
contractile component
PEC
parallel elastic component

3. Muscle Model Whole Muscle CC SEC 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
PEC CC
SEC

4. Viscoelastic Structures
Tissue
Viscoelastic Structures
SEC CC
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.

5. Stretch-Shortening Cycle
Whole
Muscle
Stretch-Shortening Cycle
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

6. Tissue Properties of Muscle
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)

7. Tissue
Muscle Structure
“Bundle-within-a-Bundle”

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

9. Sarcomere Organization
Tissue
Sarcomere Organization
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)

10. 3 sarcomeres in parallel
Sarcomere organization example:
Note that the values are not representative of actual sarcomeres.
1 sarcomere
3 sarcomeres in series
3 sarcomeres in parallel
Force
1 N
3 N
ROM
1 cm
3 cm
Time
1 sec
Velocity
1 cm/sec
3 cm/sec

11. Sarcomere Organization
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

12. Muscle Structure Fusiform (parallel)
fibers run longitudinally
generally fibers do not extend the entire length of muscle

13. Muscle Structure Pennate
Tissue
Muscle Structure Pennate
tendon runs parallel to the long axis of the muscle, fibers run diagonally to axis (short fibers)

14. Fusiform vs. Pennate Tissue fusiform pennate
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

15. Fiber Types 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)

16. Tissue

17. Tissue
Fiber Type Comparison

18. Active Length-Tension
Tissue
Active Length-Tension l0
- neither contracted
nor stretched
Length
Tension l0

19. Length-Tension Tissue l0 l0 - neither contracted nor stretched
physiological
limit
combined T
passive
active l0 L

20. Force - Velocity Relationship Tissue v < 0 (eccentric) v > 0
(concentric)
force
velocity of contraction
v=0
(isometric)

21. Tissue
Power - Velocity
Relationship F
Power (F*v) v
30% vmax

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

23. Muscle Terms Whole Muscle
attachment can be directly to the bone or indirectly
via a tendon or aponeurosis
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

24. Functions of Muscle 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

25. Functional Muscle Groups
Whole
Muscle
Functional Muscle Groups
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

26. Role of the Muscle 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

27. Whole Muscle SHOULDER ABDUCTION 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

28. Muscular Action Whole Muscle isometric action concentric 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

29. Whole
Muscle

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

31. Elbow Actions Whole Muscle push-up catching a baseball
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

32. 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 “drop-stop-pop” action with only an 8”-12” drop

33. Number of Joints Crossed
Whole
Muscle
Number of Joints Crossed
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

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

35. Insufficiency 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

36. Insufficiency Example
Whole
Muscle
Insufficiency Example
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?

37. Movement/Activity Properties of Muscle
Whole
Muscle
Movement/Activity Properties of 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

38. Movement/Activity Properties of Muscle (cont.)
Whole
Muscle
Movement/Activity Properties of Muscle (cont.)
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

39. Muscular Strength 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

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

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

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

43. Muscular Force Components
Whole
Muscle
Muscular Force Components
stabilizing or dislocating component
parallel to rotating segment
stabilizing is toward joint
dislocating is away from joint
rotary component
causes motion
perpendicular to the rotating segment

44. Muscular Force Components
Whole
Muscle
Muscular Force Components
components depend on the joint angle
large rotary
small stabilizing
medium rotary
medium dislocating
small rotary
large stabilizing

45. What Causes Motion? Force or Torque?
Whole
Muscle
What Causes Motion? Force or Torque?
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 (Fm)
muscle torque (Tm)
distance between pt of
application and joint axis
(dm)

46. Calculation of Muscle Torque
Whole
Muscle
Calculation of Muscle Torque Fm
400 N 60 o
0.03 m
To solve problem we must
resolve the vector Fm into
components which are
perpendicular (Fm ) and
parallel (Fm ) to the forearm.
Tm = Fmd *
Torque = 400 N * 0.03 m
becasue Fm is not perpendicular
to the forearm!!!

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

48. Whole Muscle T = 345 N * 0.03 m = 10.4 Nm FR = 345 N
Angle of Pull Affects Torque
400 N
0.03 m
FR = 200 N
T = 200 N * 0.03 m = 6 Nm

49. Whole Muscle T = 345 N * 0.03 m = 10.4 Nm FR = 345 N
Size of Muscle Force Affects Torque
FR = 345 N
600 N
0.03 m
T = 520 N * 0.03 m = 15.6 Nm
FR = 520 N

50. Whole Muscle T = 345 N * 0.03 m = 10.4 Nm FR = 345 N
Moment Arm Affects Torque
400 N
0.1 m
FR = 345 N
T = 345 N * 0.1 m = 34.5 Nm

51. Calculation of Muscle Torque
Whole
Muscle
Calculation of Muscle Torque Fm Fm 60 o
400 N 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

52. Factors Affecting Torque
Whole
Muscle
Factors Affecting Torque
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

53. Additional Factors Affecting Torque
Whole
Muscle
Additional Factors Affecting Torque
Muscle Force
1) level of stimulation
2) muscle fiber type
3) PCSA
4) velocity of shortening
5) muscle length
Angle of pull
Moment arm