The document discusses the musculoskeletal basis of movement, detailing the types of skeletal muscle fibers (Type I, Type IIA, Type IIB) and their characteristics. It also covers muscle classification based on shape, location, action, role, and biomechanical function, as well as different types of muscle contractions (isometric, isotonic, isokinetic) along with physiological changes during exercise. Furthermore, it provides insights into the effects of muscle contraction on joint movement and energy expenditure.

1. Musculoskeletal Basis of
Movement

2. Types of Skeletal muscle fibers
● Skeletal muscles are the voluntary and striated muscles. These skeletal
muscles are responsible for the activities or movements around a particular
joint. These skeletal muscles are not having the same structure and function.
● There are three types of skeletal muscles:
● Type I fibers
● Type IIa fibers
● Type IIb fibers

3. Type I fibers
These fibers contain more number of mitochondria, myoglobin and the blood
capillaries. Because of the more number of myoglobin and blood vessels, the
muscle fibers are red in color.It is having the capicity to generate ATP from the
aerobic system, so that it called as oxidative fibers.It is innervated by the less
number of nerve fibers. These muscle fibers are in small diameter and fatigue
resisted fibers.
Slow Twitch- Fatigue resisted - Red coloured - Oxidative muscle fibers.
Example: Postural muscles like neck, trunk and back muscles.

4. Type IIa Fibers
They contain more amounts of myoglobin, mitochondria and blood capillaries. But
comparative with type I , these are less pink in color. These are fatigue -resisted
fibers but not like Type I. They split ATP much faster , as the result contraction
velocity is also fast. These fibers also generate the ATP from aerobic system.
Oxidative - Fast twitch - pink colored -Fatigue resisted muscle fibers
Example: Calf muscles, hamstrings and quadriceps muscles.

5. Characters Type I Type IIa Type IIb
Color Red Pink White
Fatiguability Very less Slow Fast
Myoglobin More More Less
Capillaries More More Less
ATP Production Aerobic system Aerobic system Anaerobic system
Velocity of conduction Slow medium Fast
Mitochondria More More Less
Example Antigravity muscles
Postural muscles like
back and neck muscles
Leg and thigh muscles
Hamstrings, calf, biceps
brachii etc
Rapid contracting
muscles like intrinsic
hand muscles and Extra
occular muscles.
Activity Maintaining posture
(Slow and prolonged)
Walking, running and
jogging
Weight lifting, gymnastic
activities ( rapid and

6. Characterstics of muscle fibers
Tonic muscles Phasic muscles
High proportion of slow oxidative fibers High proportion of fast glycolytic fibers
Penniform (feather shape in
arrangement)
Parallel in fibers arrangement
Located deep Positioned superficially
Perform stabilizing function Perform mobility
Recruited to perform work when
endurance type activities are
performed i.e to perform low intensity
work over long periods of time.
They are particularly suited for high
intensity workbouts that can be
sustained for only short period of time.

7. Classification of muscles
● Muscles may be classified in a number of different ways. They may be
divided according to:
a) Shape
b) Location
c) Action
d) Role
e) Biomechanical function

8. ● Muscles can be classified according to their Shape and appearance.
● Shape: The deltoid (triangular), trapezius (trapezoid), serratus (saw‐toothed),
and rhomboideus major (rhomboid) muscles have names that describe their
shapes.
● Direction of muscle fibers: The terms rectus (parallel), transverse
(perpendicular), and oblique (at an angle) in muscle names refer to the
direction of the muscle fibers with respect to the midline of the body.
● Size: Maximus (largest), minimus (smallest), longus (longest), and brevis
(shortest) are common suffixes added to muscle names.

9. Arrangement of the Fasciculi of the Muscles
The muscular fasciculi are arranged in three directions:
1. Parallel
2. Oblique
3. Circular

10. Parallel
When the fasciculi are parallel to the line of pull. This fasciculi muscles having the
strong action and also higher ROM capacity. These muscles are again divided into
four varieties. They are:
i) Strap and strap like with tendinous intersections
ii) Fusiform
iii) Rhomboidal or quadrilateral
iv) Triangular

11. Rhomboidal/ Quadrilateral
These muscles are rhomboid shape or quadrangular in shape, the muscles having
the broad attachment with the broad flat tendon.
Example: Rhomboidus major, pronator quadratus, Quadratus lumborum
Triangular:
The muscles having the spreaded fasciculi, which ends with the flat and small
tendon, these are triangular or fan shaped.
Example: Pectoralis major, temporalis, adductor longus

13. Strap:
In this muscle, fasciculi are parallel with each other and run total length of the
muscles and ends in flat tendon.
Example: Sternomastoid, Stylohyoid.
Straplike with tendinous intersections :
Example: Rectus abdominis.
Fusiform:
The fasciculi are parallel to each other and runs full length of the muscles and
terminate in the flat tendon. But the muscular part is more bulky in middle than the
tendon.
Example: Biceps brachii, Brachioradialis

15. Oblique muscle fibers
When the fasciculi are oblique to the line of pull, the muscle may be triangular , or
pinnate in the construction. This arrangement makes the muscle more powerful
although the range of movement is reduced , oblique arrangements are of the
following:
The muscles are having the strong fibers but less ROM capacity muscles. There
are three varieties.
1. Unipinnate
2. Bipinnate
3. Multipinnate

17. Unipinnate
The muscular fasciculi are arranged in the one side of the tendon.
Example: Tibialis anterior , EDL and semi membranosus.
Bipinnate
Fasciculi arranged in both sides of the tendon
Example: Interosseus muscles of the hand.
Multipinnate
Many tendons are having both the side fasciculi arrangement
Example : Deltoid

18. Spiral or twisted fibers
● Spiral and twisted fibers are found in Trapezius, Pectoralis major, Latissimus
dorsi , supinator etc.. In certain muscles fasciculi are crossed . These are
called as cruciate muscle.
● Example : Sternocleidomastoid and adductor magnus

20. b) Location: Muscles can be classified according to their location or attachment.
● Skeletal muscles are often named after the following characteristics:
● Number of origins: Biceps, triceps, and quadriceps indicate two, three, and
four origins, respectively.
● Location of origin or insertion: The sternocleidomastoid names the sternum
(“sterno”) and clavicle (“cleido”) as its origins and the mastoid process of the
temporal bone as its insertion, Coracobracialis
● Location: In addition to its origin or insertion, a muscle name may indicate a
nearby bone or body region. For example, the temporalis muscle covers the
temporal bone.

21. c) Action: Terms such as flexor (flex the arm), extensor (extend the arm),
abductor (move the arm laterally away from the torso), and adductor (return the
arm to the torso) are added as prefixes to muscle names to indicate the kind of
movement generated by the muscle.
Example: flexor hallucis longus, extensor digitorum

22. d) Role: Muscles can be classified according to the role they perform like
i) Agonist: one muscle or group of muscles actively contract to produces
particular movement of a joint and is/are called a primary mover (eg) biceps
brachii is main flexor of forearm
ii) Antagonist: Any muscle that opposes the action of the prime mover is an
antagonist. Before a prime mover can contract, the antagonist muscle must
be equally relaxed. (eg) triceps brachii is antagonist to biceps brachii .
The biceps is tri-articulate, meaning that it works across three joints. The most
important of these functions are to supinatethe forearm and flex the elbow.

23. ● Fixators: A fixator contracts isometrically (i.e., contraction increases the tone but
does not in itself produce movement) to stabilize the origin of the prime mover so
that it can act efficiently. For example, the muscles attaching the shoulder girdle to
the trunk contract as fixators to allow the deltoid to act on the shoulder joint.
● Synergists: (Syn = with)In many locations in the body the prime mover muscle
crosses several joints before it reaches the joint at which its main action takes
place. To prevent unwanted movements in an intermediate joint, groups of
muscles called synergists contract and stabilize the intermediate joints. For
example, the flexor and extensor muscles of the carpus contract to fix the wrist
joint, and this allows the long flexor and extensor muscles of the fingers to work
efficiently. The synergists are acting with the agonists and making stronger the
action of agonists.

24. Types of muscle work
● Isometric contraction
● Isotonic contraction
● Isokinetic contraction

25. Isometric contraction
● Iso- same and metric- measure or length
● In isometric contraction there is no changes in the length of the muscle but the
tension.
● There is no mechanical muscle work occurs in isometric contraction because the
force is generated, i.e. tension is created but is not moving a bony lever because
both the proximal and distal bones are fixed here.
● An Isometric contraction occurs when the ends of the muscle do not move during
contraction i.e although muscle contracts but length of the muscle remains the
same and no external work is done.
● Any shortening in muscle length which occurs due to contraction of contractile
component (thick and thin filaments) get compensated by stretching of series
elastic component, therefore length of the muscles remains constant but the
tension in it increases gradually.

26. ● Muscles consists of contractile component which represents elasticity of
thick and thin filaments. It comprises of 3/5th of total muscle protein.
● The contractile component is: In Parallel with elastic component which
represents the elasticity of structural elements eg: connective tissue sheath
(PEC)
● In series with another elastic component which represents elasticity of
tendon etc known as series Elastic component (SEC)
● Resistance to stretch is mainly due to SEC and PEC.
● Since muscle is not a complete elastic component, therefore it doesnot obey
the Hooks law, i.e, when resting muscle is stretched the tension produced is
not proportional to stretch applied.
● No external work is done
● ( work done = Force x distance)
● Experimentally Isometric contraction occurs in preload preparation, i.e
weight will act on muscle before it begins to contract.

27. Isotonic contraction
● Iso = Equal, Tonic= tone
● By changing the length of a muscle , the same amount of tension is created
throught the contraction is said to be isotonic contraction.
● Experimentally, Isotonic contraction is studied when muscle is subjected to
after load preparation.
● On stimulation when the muscle contracts , contractile component shortens
parallel and stretches the series elastic component, therefore muscle tension
increases (initial portion of contraction is isometric) when the force developed
by the muscle just exceeds the effect of weight , the muscle as a whole
begins to shorten , thereafter the tension in the muscle remains constant
throught the remainder of shortening and contraction recorded is due to
shortening of contractile component.

28. ● Duration of initial part of Isometric contraction increases, because series
elastic component must stretch more to transmit the force required to lift the
greater 'afterload'.
● There are two types of isotonic contractions:
● Concentric contraction
● Eccentric contraction

29. Concentric Contractions
● Concentric- towards the centre
● This type of contraction is otherwise called as shortening contraction.
● The muscle is isotonically shortens to produce the movement. The proximal
and distal bones are drawn towards the centre.
● Normally , one bony component is fixed and another will be moving to
perform the movement.
● If the proximal bony component is fixed the distal bony component will be
pulled towards the center. Eg. Lifting the dumbells.
● If the distal component is fixed the proximal bony component moves towards
the center. Eg. Push ups.
● W= F X D

30. Eccentric contraction
● Eccentric- from the center
● This is otherwise called as lengthening contraction.
● Here the proximal and distal bony components are pulled apart from the centre.
● Eccentric contraction lengthens the muscle and the insertion of the muscle is
pulled distally.
● The energy expenditure in this contraction is very less than the concentric
contraction. The muscular tension moves the bony lever through a distance in
the direction of the muscle pull. But the muscle work is said to be negative
muscle work.
● Normally, these eccentric contractions are assisted by the gravitational force.
The contraction occurs inside the muscle even though it lengthens.

31. ● Eccentric contraction occurs when the total length of the muscle increases as
tension is produced. For example, the lowering phase of a biceps curl
constitutes an eccentric contraction. Muscles are capable of generating
greater forces under eccentric conditions than under either isometric or
concentric contractions.Large tensile forces are generated during sudden
eccentric contractions

32. Isokinetic Contractions
● Iso= same, kinetic= speed
● An isokinetic muscle contraction occurs when the velocity of the muscle
contraction remains constant while the length of the muscle changes. The
force exerted by the muscle is not fixed, and can vary depending on the
position of the joint in its range of motion and the participation effort of the
subject.
● Isokinetic muscle loading can be either concentric or eccentric. In an
isokinetic concentric contraction, the muscle shortens while under load. In an
isokinetic eccentric contraction, the muscle lengthens while under load.
● In Isokinetic contractions, the velocity or speed is same and the resistance is
variable.
● This type of exercise can be done with the help of the special equipment such
as Biodex, Cybex, Kincom, Orthron.

33. ● The speed and velocity is preset and the resistance is directly proportional to
the torque produced by the muscle.
● The speed is constant ; if the patient wants to increase the speed , it is not
possible . If the patient offers more force , the resistance exerted by the
instrument will be more.
● Normally in the middle range , muscle has more strength than in the
beginning and in the end range.If the resistance stays same throughout the
ROM, the muscle has to work harder in beginning and in the end range, so
that the speed also varies throughout the ROM. But in isokinetic exercise
whatever the torque produced in the muscle same amount of resistance
produced by the instrument.
● In the middle range the strength of the torque is more, so that the resistance
given by the equipment also more. Sometime is the beginning and end range
is less. So, this disadvantage is not seen in isotonic or isometric contraction
and exercise.

34. ● The tension created inside the muscle changes depend on the type of muscle
contraction; the tension generated in the eccentric contraction is more than
the other contraction.
● Eccentric> Isometric> concentric

35. Range of muscle work
● Range of muscle work means the degree of the movement done by the
muscle contraction. To produce a movement the group of muscles has to
contract and stretch. There are four types of ranges:
● 1) Full range:- The muscle is moving the joint from the full stretched position
to full contracted position. (concentrically) or from the contracted position to
full stretched position (Eccentrically). The full range of movement rarely
required in normal day to day activity. Full range exercises are required to
perform by the patients to maintain the full ROM of the joints.
● 2) Inner range:- The muscles move the joint from the medium contracted
position to the full contracted position (concentrically) or from minimum
contracted position to full stretched position (Eccentrically). Extreme inner
range movements are difficult to perform and it requires the more numbers of
motor unit contractions.

36. Type IIb Fibers
They contain less numbers of mitochondria, myoglobin and blood capillaries. They
generate the ATP from the anaerobic system, i.e. by the process of glycolysis.
They are large in diameter fibers and are fatigue earlier. The contraction of these
muscle fibers will be more rapid and strong. These muscle fibers also contain the
glycogen , they are in white color.
Glycolytic - Fast twitch - Early fatiguable -White muscle fibers.
Example: The muscle responsible for rapid movements like intrinsic muscle of
hands and eye muscles.

37. ● 3) Middle range:- Muscle moves the joints between the minimal range to the
medium range. There is no fully stretched or fully contracted muscles seen.
This is the range which we use more in our day to day life.In this range the
muscle has the maximum strength . exercise in this range increases the
muscle power, strength and tone.
● 4) Outer range:- The muscles move the joint from the stretched position to the
minimal contracted position (concentrically) or from full contracted to the
medium contracted position. Outer range movements also are very much
difficult to perform. While performing the outer range movement , the angle of
pull will be adverse and some of the energy is used for the compression of
the articular surface. The gravity also resist the movement , so that outer
range movement will be difficult to perform.

38. Physiological changes during exercises
● Increasing muscular activity needs the more Oxygen and RBC supply to the
acting muscles. This can be done by:
● By increasing heart rate
● By increasing BP
● By increasing cardiac output
● By increasing venous return
● By reducing blood flow to the inactive muscles and non vital organs.
● By redistributing the blood from the non vital organ to vital organ.

39. Changes in Cardiovascular System
● Effect on heart
● Effect on heart rate
● Effect on cardiac output
● Effect on venous return
● Effect on Blood pressure
● Effect on circulation

40. Changes in Respiratory system
● Pulmonary ventilation
● Respiratory rate
● Effect on second wind
● Effect on Oxygen exchange

41. Changes in blood cell
● Changes in Blood tempretaure
● Changes in blood fluid
● Effect on kidney function
● Digestive system
● Endocrine function