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BPK 143 (50)
Chapter 4

Kin 143 Chapter 4 Notes

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Biomedical Physio & Kines
BPK 143
Tony Leyland

Chapter 4 Muscular Strength and Endurance Benefits of Resistance Training  Increases o Muscular Strength o Muscular Endurance o Stamina o Flexibility o Speed and Power o Blood Volume and Hemoglobin  Decreases o Body Fat o Stress and Tension o Resting Heart Rate  Helps to o Prevent Injuries o Rehabilitate Injuries o Improve cardio-respiratory function o Alter metabolism to improve caloric utilization o Facilitate quicker recovery from workouts and competitions Disadvantages of Strength Training  Increased risk of o Muscle and Tendon Injuries o Bone and Ligament Injuries o Low back Injuries o Contact with weight plates causing injury (more likely free weights) o Large transient increases in systolic blood pressure (SBP) o Excessive fatigue due to over training Definitions  Muscular Strength o The greatest amount of force that a muscle or muscle group can produce in a single maximal effort  Muscular Endurance o The ability of a muscle group to perform repeated contractions against a light load for an extended period of time  Muscular Power o The ability to produce force quickly. o Force * Distance Types of Muscular Contraction  Isometric Contraction o No change in length of muscle (stretches,planks) o Muscular contraction with no change in length of the muscle o Disadvantage  Strength is not increased throughout the joint’s range of motion but is specific to the joint angle at which the training is performed  Does not optimally improve the ability to exert force rapidly  Motivation is poor  Strength-type activities, causes large increases in arterial blood pressure and workload of heart  Isotonic Contraction o Tension is constant (leg curls, pushups, etc) o Muscular contraction where the tension (force) in the muscle is constant o Rarely occurs o Moving constant mass (weight) such as a barbell or your body weight  Isokinetic Contraction o Muscle Shortens or Lengthens at a Constant Velocity o Muscle shortens or lengthens at a constant velocity o Working on a machine that controls the velocity of movement  Concentric Contraction o Muscle is contracting and shortening o Unique property of muscle tissue  Eccentric Contraction o Muscle is not only contracting but also lengthening o Muscle is trying to shorten – muscle only pull, they can’t push – but an external force is causing the muscle to be lengthened o Example. Gravity Muscle Fibre Types  Motor Unit o Single motor neuron and all the corresponding muscle fibres it innervates (causes to contract) o Classifications  Speed of Contraction  Slow or fast  Metabolic Characteristics  Muscle Physiologists  Type I (SO) o Slow Twitch (ST) o Slow Twitch Oxidative  Type IIa (FOG) o Fast Twitch (FT) o Fast Twitch Oxidative Glycolytic  Type IIx (Type IIb) (FG) o Fast Twitch (FT) o Fast Twitch Glycolytic  Fibres  Slow Twitch o Adapted for prolonged work o Used extensively for aerobic activities (distance running) o Contains large concentration of myoglobin  Iron-containing protein that reversibly binds with oxygen molecules and is stored within skeletal muscle  Fast Twitch o Generate energy rapidly for quick, forceful contractions o Essential for high-intensity events  Size Principle o Smaller Type I motor neurons are recruited first Muscle Mechanics  Muscle Size (Cross-Sectional Area) o No physiological difference between male and female muscle  Time Course of Contraction o Electro-Mechanical Delay  Short period for the force to build up to maximum when you first contract a muscle  As motor units are recruited, the tendon stretches  Muscle Activation o All-or-nothing law  Either a muscle fibre is “on”, exerting maximal force, or it is
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