Muscular contractions

Muscular contractions

1. Muscular Contractions

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 contractions Isometric: 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.

7. 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

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

9. 1. Arrangement of Muscle Fibres Fusiform Penniform Unipennate Bipennate Multipennate

10. 1. Arrangement of Muscle Fibres a ) 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: Unipennate Bipennate Multipennate

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

12. 1. Arrangement of Muscle Fibres

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

14. 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

15. 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

16. Characteristics of Muscle Fibre Types

17. 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.

18. 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