The document defines and describes different types of muscle work. Static work involves maintaining posture or joint position through muscle contraction without mechanical work, while dynamic work produces mechanical work and joint motion. Static work includes isometric contractions that generate force without changing muscle length. Dynamic work includes isotonic contractions where tension is constant during motion, as well as isokinetic and isoinertial contractions where velocity or resistance remains constant during motion.

1. TYPES OF
MUSCLE WORK

2. Content
Definition of Muscle work
Types of muscle work
Static work
Dynamic work
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3. Definition
“A muscle fiber generates
tension when properly
stimulated, by the nervous
system or by electrical
impulses. This physiological
process is called muscle
contraction.”
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4. Types of Muscle Work
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5. Types of Muscle Work
Types of
muscle
Static work
Dynamic
work
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6. Types of Muscle Work (cont…)
Static work
• No mechanical work is
performed
• posture
or joint position is
maintained through the
muscle contraction.
Dynamic work
• Mechanical work is
performed
• joint motion is
produced through the
muscle contraction.
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7. Static Muscle Work
Static
work
Isometric
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8. Isometric Muscle Contraction
When a muscle contracts,
producing force without changing
the length of muscle.
Muscles are not always directly
involved in the production of joint
movements.
They may exercise either a
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9. Isometric Muscle Contraction
(cont…)
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10. Dynamic work
Dynamic work
1.Isotonic
A.Concentric
B.Eccentric
2.Isokinetic
3.Isoinertial
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11. 1. Isotonic Muscle
Contraction
 This term is commonly used to define
muscle contraction in which the tension is
constant throughout a range of
motion.
 Two types:
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A. Concentric
B. Eccentric

12. Concentric Muscle
Contraction
 When there is joint movement, the muscles
shorten, and the muscle attachments move
toward each other.
 When muscles develop sufficient tension to
overcome the resistance of the body
segment, the muscles shorten and cause
joint movement.
 Positive work is being done by the muscle
because the joint moves through a ROM.
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13. Concentric Muscle Contraction
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14. Concentric Muscle Contraction
 Action of the quadriceps in extending the
knee when ascending the stairs.
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15. Eccentric Muscle Contraction
When there is joint motion, the muscle
appears to lengthen; that is, the
muscle attachments separates.
When a muscle cannot develop
sufficient tension & is overcome by
the external load, it progressively
lengthens instead of shortening.
Negative work because the work is
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16. Eccentric Muscle Contraction
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17. Eccentric Muscle Contraction
 Quadriceps works eccentrically to
decelerate flexion of the knee during
descending the stairs.
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18. 2. Isokinetic Muscle Work
With an isokinetic contraction,
resistance to the part varies, but
the velocity, or speed stays
constant, hence the velocity of
shortening or lengthening of the
muscle is constant.
It can be done only with special
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19. 3. Isoinertial Muscle Work
The resistance against which the
muscle must contract remains
constant.
Isoinertial contraction occurs
when a constant external load is
lifted.
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20. 3. Isoinertial Muscle Work
(cont…)
If the moment (torque) produced by
the muscle is equal to or less than the
resistance to be overcome, the
muscle length remains unchanged
and the muscle contracts
isometrically.
If the moment is greater than the
resistance, the muscle shortens
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21. References
1.Pamela K. Levangie, Cynthia C. Norkin. Joint structure
and function. Fourth edition.
2.Margareta Nordin, Victor H. Frankel. Basic Biomechanics
of the Musculoskeletal system. Thied edition.
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