4. Muscle Tissue Characteristics Excitability Nerve stimuli controls muscle action. Muscles can receive and respond to a stimulus from a nerve cell. Contractibility Muscle changes shape due to a stimulus. That is, can become shorter and thicker. Elasticity Muscle returns to normal length when force is removed. That is, after is has been contracted. Extensibility Muscles have the capacity to stretch when a force is applied. Atrophy – muscles can decrease in size as a result of injury, illness or lack of exercise. Hypertrophy – muscles can increase in size with an increase in physical activity
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7. Muscle Action and Movements During a particular movement, a muscle performs one of the following roles: Agonist or Prime Mover – This muscle causes the major action. There is usually more than one prime mover in a joint action, and there are prime mover muscles for all moveable joints. Antagonist – This muscle must relax and lengthen to allow a movement to occur. It causes an opposite reaction to that caused by the agonist. Generally, muscle flexors and extensors work in an agonist – antagonist relationship. Synergist or assistant – This muscle assists the agonist to produce the required movement to reduce any excessive or unnecessary movements. Stabiliser or fixator – these muscles ensure that the joint remains stable while the agonist and antagonist are working. The muscle will shorten just slightly during contraction, causing only minimal movement to allow the action to be performed more effectively.
46. The relationship between the three energy systems Area On Chart Performance Time Major Energy System(s) Involved Example A Less Than 30 Seconds ATP-PC System 100m Sprint B 30 to 90 Seconds ATP-PC System Lactic Acid System 200m - 400m Sprint 100m Swim C 90 Seconds to 3 Minutes Lactic Acid System Oxygen System Boxing (3m Rounds) 800m Run D Over 3 Minutes Oxygen System Aerobics Class Marathon
49. Definitions VO2 Oxygen uptake. The amount of oxygen taken up and used by the body VO2 max The greatest volume of oxygen used by the cells of the body within a given time. Steady state State of stability where the energy demands can be met relatively easily for a prolonged period of time. O2 deficit The amount of oxygen taken in above what is normally used at resting levels. EPOC The amount of oxygen required for pay back in recovery Alactic acid debt EPOC supplies the energy for phosphagen replenishment (anaerobic). Lactic acid debt EPOC that supplies energy for the removal of lactic acid (aerobic). Anaerobic threshold The intensity effort at which lactic acid accumulates. Aerobic threshold Sub-maximal steady state of 130 – 150 bpm. Cardiac output The volume of blood pumped from a ventricle per unit of time. It is the product of HR and SV. Stroke volume The amount of blood pumped out of the ventricles with each beat. Arterio-venous O2 difference The difference in oxygen content between the arterial blood and the mixed venous blood in the right atrium. Tidal volume The amount of air breathed in and out in one breath. Hypertrophy Increased cell size leading to increased tissue size.
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