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Muscles at Work

Muscles at Work. Chapter 4. Objectives. To be able to identify and describe the different types of muscle contractions To identify the components of strength To gain an understanding of the relationships among strength components To describe the factors that influence strength development

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Muscles at Work

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  1. Muscles at Work Chapter 4 Sport Books Publisher

  2. Objectives • To be able to identify and describe the different types of muscle contractions • To identify the components of strength • To gain an understanding of the relationships among strength components • To describe the factors that influence strength development • To evaluate resistive force and power patterns of exercise devices • To analyze sports movements and make movement-oriented exercise prescriptions Sport Books Publisher

  3. Types of Muscle Contractions Sport Books Publisher

  4. Types of Muscle Contraction Forms and types of muscle contraction Dynamic Static Isotonic Auxotonic Isokinetic Isometric Plyocentric Concentric Eccentric Concentric Eccentric (overcoming, accommodating) (resistive) Sport Books Publisher

  5. Types of Muscle Contraction Forms and types of muscle contraction Static Dynamic Sport Books Publisher

  6. Types of Muscle Contraction Forms and types of muscle contraction Static Isometric Concentric Eccentric Sport Books Publisher

  7. Types of Muscle Contraction Forms and types of muscle contraction Dynamic Auxotonic Isokinetic Plyocentric Isotonic Sport Books Publisher

  8. Types of Muscle Contraction Dynamic Isotonic Auxotonic Isokinetic Plyocentric Concentric Eccentric (overcoming, accommodating) (resistive) Sport Books Publisher

  9. Forms and types of muscle contraction Dynamic Static Isotonic Auxotonic Isokinetic Isometric Plyocentric Concentric Eccentric Concentric Eccentric (overcoming, accommodating) (resistive) Types of Muscle Contraction Sport Books Publisher

  10. Static Contraction • Muscle tension or internal force exerted against an external load • Internal force is equal to, or weaker than, the external load • No visible movement of the external load occurs Sport Books Publisher

  11. Static Contraction • In most sports, the need for maximal static contraction is rare • Maximal static contraction is most often seen in gymnastics, wrestling, and judo Sport Books Publisher

  12. Activities Requiring Maximal Static Muscle Tension Sport Books Publisher

  13. Static Contraction • Most sports require low to sub-maximal static contraction • Examples of sports that require this type of contraction include sail-boarding, alpine skiing, and shooting events Sport Books Publisher

  14. Activities Requiring Sub-Maximal Static Muscle Tension Sport Books Publisher

  15. Dynamic Contraction • Muscle tension or force is exerted against an external load • Internal force exerted is greater than the external load • Visible movement of the external load occurs Sport Books Publisher

  16. Isometric Contraction • A static contraction • Muscle contraction against an external force • No visible change in muscle length • External load is greater than the force generated by the internal force • No external movement occurs • No work is performed because no movement occurs • A high amount of tension is developed, energy is used Sport Books Publisher

  17. Pushing against a stable wall is an example of an isometric contraction Sport Books Publisher

  18. An isometric contraction occurs during an arm wrestling match when opponents generate equal forces Sport Books Publisher

  19. Auxotonic Contraction • A dynamic contraction • During dynamic work, continual changes in joint angle and speed result in changes in strength needs • That is, the tension required to move an external load varies • The involvement of more or less motor units allows the muscle to adapt to changing tension requirements Sport Books Publisher

  20. Auxotonic Contraction • For example, the strength needed to perform a barbell curl depends on a number of internal factors • These factors include: • The athlete’s physique • The athlete’s leverage • The angle position of the limbs • The speed of the movement Sport Books Publisher

  21. Auxotonic Contraction • Although the weight of the barbell remains the same, these factors may compromise an athlete’s capacity for strength gains at all joint angles • Therefore, it is not easy to gain equal strength gains at all joint angles when training with free-weights alone Sport Books Publisher

  22. Isotonic Contraction • A dynamic contraction • A change in muscle length occurs • Constant tension is achieved and maintained • Rarely encountered in sports and athletic events because a change in tension is usually required with a change in joint angle Sport Books Publisher

  23. Isotonic Contraction • Lowering a heavy weight at a slow and constant speed is an example of an isotonic contraction Sport Books Publisher

  24. Isokinetic Contraction • A dynamic contraction • Involves a constant speed contraction against a preset high resistance • Generation of a high level of tension within a muscle at all joint angles • Thus, muscle strengthening also occurs at all joint angles • With the use of certain machines, constant tension can be achieved as joint angle and movement velocity are controlled Sport Books Publisher

  25. Examples of dynamometers that allow for isokinetic contraction include: CYBEX KINCOM LIDO HydraGym Nautilus Isokinetic Contraction Sport Books Publisher

  26. Concentric and Eccentric Contractions Concentric Contraction: Involves muscle shortening as it goes through a range of motion; usually termed flexion Eccentric Contraction: Involves muscle lengthening during movement; usually termed extension Sport Books Publisher

  27. Examples of Concentric & Eccentric Contractions Moving the heel closer to the buttocks is an example of a concentric contraction of the hamstring Moving the heel away from the buttocks is an example of an eccentric contraction of the hamstring Sport Books Publisher

  28. Plyocentric Contraction • A hybrid contraction • The muscle performs an isotonic concentric contraction from a stretched position • Involves a “pre-stretching” of the muscle to initiate the Golgi tendon organ reflex • The reflex causes the muscles to contract • Plyocentric training can result in functional strength gains beyond those that can be achieved through strength training alone Sport Books Publisher

  29. Plyocentric Training Sport Books Publisher

  30. Factors Influencing Muscle Contraction Sport Books Publisher

  31. Factors Influencing the Force and Power of Muscle Contractions: • The individual’s state of health • The individual’s training status • Joint angle • Muscle cross-sectional area • Speed of movement • Muscle fibre type • Age • Gender Sport Books Publisher

  32. Joint Angle • The type of contraction and the force required to resist an external load change as the joint angle changes • The contraction type and force required depend on whether the external force exceeds, or is less than, the internal (applied) force • Static, dynamic, concentric, and eccentric contractions may all be required • Coordination between agonist and antagonist muscles is required Sport Books Publisher

  33. Joint Angle Maximal force is produced at a joint angle that corresponds to maximal cross-bridge interaction Sport Books Publisher

  34. Muscle Cross-Sectional Area • Body mass is positively correlated with strength, provided that the mass is primarily muscle tissue or lean mass • The larger the muscle cross-sectional area, the more force it can generate Sport Books Publisher

  35. Muscle Cross-Sectional Area Sport Books Publisher

  36. Muscle Cross-Sectional Area • The heaviest weights of all are lifted by athletes in the super-heavyweight category Sport Books Publisher

  37. Maximal and Absolute Strength • The greater the active body mass, the greater the maximal or absolute strength • However, individuals of a smaller and lighter physique may possess a relatively high strength potential when the following factors are considered: • Intramuscular coordination • Intermuscular coordination • Anatomical structure • Muscle elasticity Sport Books Publisher

  38. Maximal and Absolute Strength • Maximal and absolute strength are important to athletes who are required to overcome the resistance of a partner or equipment Sport Books Publisher

  39. Relative Strength • The performance of athletes classified by weight, or athletes who must overcome their own body mass, depends on the proportion of maximal strength to body mass Relative Strength = Maximal Strength Body Mass Sport Books Publisher

  40. Relative Strength • Gymnasts rely heavily upon the development of relative strength Sport Books Publisher

  41. Relative Strength • Recreational athletes are usually interested in increasing active strength and reducing body mass • This method is also used by overweight athletes who want to lose fat mass Sport Books Publisher

  42. Relative Strength • Relative strength can also be gained by increasing strength and stabilizing body mass Sport Books Publisher

  43. Relative Strength • Young recreational athletes should strive to develop strength in addition to increasing active body mass Sport Books Publisher

  44. Speed of Movement • As speed of movement increases, the force a muscle can generate decreases • Cross bridges are compromised since they cannot couple and uncouple fast enough • Thus, there is a decreased ability to establish and maintain a large number of cross bridges Sport Books Publisher

  45. Speed of Movement • Three main components of strength related to speed of movement are: • Maximal strength • Power • Muscular endurance Sport Books Publisher

  46. Maximal Strength Maximal Strength: The ability to perform maximal voluntary muscular contractions in order to overcome powerful external resistances One Repetition Maximum (1RM): The greatest force that can be exerted during one repetition for a given contraction of muscles Sport Books Publisher

  47. From Greek Mythology… • The alertness and great strength of Hercules, the hero of Greek mythology, allowed him to perform extraordinary deeds • The name Hercules suggests a human being of giant stature and great physical strength Sport Books Publisher

  48. Maximal Strength • Greater absolute strength is necessary for activities such as weightlifting and field events in track & field Sport Books Publisher

  49. Power Power: The ability to overcome external resistance by developing a high rate of muscular contraction; also known as ‘speed-strength’ Sport Books Publisher

  50. Power • Important for performance in activities that require mastering quick movements • Includes sprinting, speed-skating, jumping, throwing, rowing, etc. Sport Books Publisher

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