Muscular contractions

1. CONTRACTION
S

2. COMMON MUSCLE
FEATURES
•Nervous control
•Contractibility
•Extensibility (Stretch when force is applied)
•Elasticity (Return to original size after
stretching)
•Atrophy-muscle mass decline as a result of non-
use
•Hypertrophy-muscles grow larger with training

3. TYPES OF MUSCULAR
CONTRACTIONSIsometric: A muscle contraction where there is no change in its
length
Isotonic: There are two types of isotonic contractions:
concentric and eccentric.
In a concentric contraction, the muscle tension rises to meet the
resistance, then remains the same as the muscle shortens.
In eccentric, the muscle lengthens due to the resistance being
greater than the force the muscle is producing.
Isokinetic:
Isokinetic contractions are similar to isotonic in that the muscle
changes length during the contraction, where they differ is that
Isokinetic contractions produce movements of a constant speed.
Generally used for rehab.

4. TYPES OF MUSCULAR
CONTRACTIONS
Isometric:
Isotonic:
Isokinetic:
Eccentric:
Concentric:

5. HOW ARE MUSCULOSKELETAL
MOVEMENTS POSSIBLE?
•The origin is where the muscle is attached to a stable
bone.
•The insertion is where the muscle attaches to the bone
which will be pulled/moved.
•What is the insertion and origin of the biceps muscle?

6. HOW ARE MUSCULOSKELETAL
MOVEMENTS POSSIBLE?
•For movement to occur a muscle must cross between two bones.
Tendons connect muscle to bone.
•Muscles can either contract or relax.
•Muscle contracts making angle smaller between the two bones.
•Muscles never work alone…
–Agonist = The muscle that creates the movement. “Prime
mover”.
–Antagonist = The Muscle that relaxes and allows the movement
to occur.
•This is called reciprocal inhibition.

8. ASSISTANTS
• Fixator or stabilising muscles provide stability to the origin of
the muscle.
• Eg. trapezius stabilises shoulder during elbow flexion
• Synergist or assistant muscles assist with producing the required
movement or reduce unnecessary movement
• Eg. Brachialis and brachioradialis (elbow flexors) assist with elbow
flexion

9. Characteristics and
Functions of Skeletal Muscle
Fibres
Muscular strength is dependent
on:
1. Arrangement of muscle fibres
2. Muscle fibre type
3. Gender and age differences
4. Recruitment of muscle fibres
(Discussed later)

10. 1. Arrangement of Muscle
Fibres
a)Fusiform
b)Penniform
i. Unipennate
ii. Bipennate
iii.Multipennate

11. 1. Arrangement of Muscle
Fibresa) Fusiform
• The muscle fibres run the length of the muscle belly.
• Designed for mobility – low force over a long range
• Example: Sartorius and Bicep
b) Penniform
• Fibres run at angles to the tendon.
• About 75% of all skeletal muscles.
• Has three subcategories:
i. Unipennate
ii. Bipennate
iii. Multipennate

12. 1. Arrangement of Muscle
Fibresb) Penniform
i. Unipennate
•Fibres are found on only one side of
a central tendon
•E.g. Tibialis Anterior
ii. Bipennate
•The fibres run off either side of a
central tendon
•Example: Rectus femoris
iii. Multipennate
•Fibres branch out from several
tendons.
•This arrangement enables the body
the generate the greatest force.
•Example: Deltoid

13. 1. Arrangement of Muscle
Fibres

14. 2. Muscle Fibre Type
Two Categories of Muscle Types:
a)Slow Twitch (Type I)
b)Fast Twitch (Type II)
• The percentage of each muscle fibre type
is genetically determined and cannot be
changed with training.

15. 2. Muscle Fibre Type
Slow Twitch
• Type 1
• Slow breakdown ATP
• Slow contraction speed
• Red in colour.
• Resistant to fatigue
• Suitable for long distance events

16. 2. Muscle Fibre Type
• Type 2A
–Resistant to fatigue
–Partially aerobic
–Red
–Fast breakdown ATP
–Fast contraction speed
• Type 2B
–White
–Fast breakdown ATP
–Fast contraction speed
–Fatigue easily
–Anaerobic

17. Characteristics of Muscle Fibre
Types

18. 3. Gender and Age
Differences
• Muscular power is dependent on gender, size,
age and physical training.
• Higher levels of testosterone in males allows
increased muscle mass development beginning in
puberty.
• Strength peaks at ages 20-30 and then decrease
1% per year.

19. • Acute responses to exercise depend in the type,
intensity and duration of activity and also the
muscle fibre type recruited
–Increase motor unit and fibre recruitment
–Increase blood flow to muscles
–Increase muscle temperature
–Increased O2 supply and utilisation
–Depletion of muscle energy stores
The Muscular System and Physical
Activity