Text of VCE Physical Education - Unit 3 Chapter 6 Muscular Fatigue Mechanisms Text Sources 1.Nelson Physical...
VCE Physical Education - Unit 3 Chapter 6 Muscular Fatigue Mechanisms Text Sources 1.Nelson Physical Education VCE Units 3&4: 4 th Edition Malpeli, Horton, Davey and Telford 2006. 2. Live It Up 2: 2 nd Edition Smyth, Brown, Judge, McCallum and Pritchard 2006.
VCE Physical Education - Unit 3 Types of fatigue FatigueDescriptionExample LocalFatigue in specific muscle group Biceps during bicep curls Quads in snowboarding GeneralFatigue in all muscles groupsAfter completing full weights session Playing a full game of football etc. ChronicUnhealthy level of fatigue, caused by breakdown of bodys defences. Chronic fatigue syndrome Overtraining Reoccurring illness or injuries
What is Fatigue? Muscular Fatigue Mechanisms
VCE Physical Education - Unit 3 What is Fatigue? Fatigue occurs when the body is unable to function at its optimal level. The muscles are unable to exert maximal force levels as a result of exercise. Fatigue occurs through everyday physical activity. Exercise increases the physiological effects of fatigue.
Causes of Fatigue Muscular Fatigue Mechanisms
VCE Physical Education - Unit 3 Causes of Fatigue Our response to fatigue depends on; 1. The muscle fibre being used 2. Types of muscular contraction occurring 3. Depleted fuel stores (Glycogen / PC and other phosphate compounds) 4. Energy Systems used and the ability to extract energy 5. The amount of metabolic by products being produced 6. Changes in blood flow and increased body temperature 7. The athletes hydration levels A number of underlying processes that also determine the level of muscular fatigue include; The type, intensity and duration of the activity The fitness level and mental state of the performer.
Fuel stores (PC and glycogen) Metabolic By-products (LA, H +, P i, Creatine) Energy pathways Causes of Fatigue Hydration levels Blood flow & redistribution Body Temperature
VCE Physical Education - Unit 3 Complete questions 1-4 page 134 of Nelson Physical Education VCE Units 3 & 4. Checkpoints
1. Muscle Fibre Types Muscular Fatigue Mechanisms
VCE Physical Education - Unit 3 Muscle Fibres Muscle fibre types can be broken down into two main types: Slow twitch (Type I) muscle fibres and Fast twitch (Type II) muscle fibres [Contains Type II a and b] Human muscles contain a genetically determined mixture of both slow and fast fibre types. On average, we have about 50% slow and 50% fast fibres in most of the muscles used for movement. Slow Twitch (Type I) The slow muscles contain more mitochondria and myoglobin which make them more efficient at using oxygen to generate more fuel (ATP) for continuous, extended muscle contractions over a long time. Fast Twitch (Type II) Because fast twitch fibres use anaerobic metabolism to create fuel, they are much better at generating short bursts of strength or speed but fatigue more quickly. Fast twitch fibres are able to fire more rapidly than slow twitch, hence their name. The slow twitch fibres, on the other hand, fire more slowly, but can go for a long time before they fatigue.
VCE Physical Education - Unit 3 Muscle Fibre Type Summary
VCE Physical Education - Unit 3 Contraction Types Isotonic Isometric Isokinetic Muscle Lengthens No change in length Contraction through full range of motion
3. Depletion of Fuels Muscular Fatigue Mechanisms
VCE Physical Education - Unit 3 Fuel Depletion Most commonly exhausted energy stores are PC and glycogen. Stores of glycogen in the muscle and liver can fuel continuous exercise for over 90 mins. Muscle glycogen is generally the first fuel source used during aerobic exercise; then liver glycogen and eventually blood-borne and stored fat. Fat conversion to energy is far less efficient than that for glycogen, resulting in a reduced intensity. As energy stores are continually depleted, fatigue occurs and therefore the quality of performance decreases
VCE Physical Education - Unit 3
4. Energy Systems Muscular Fatigue Mechanisms
VCE Physical Education - Unit 3 4. Aerobic Pathway & Fatigue Aerobic Exercise Less than 20 minutes; No major fatigue and carbos and fats used as energy (Very little lactic acid). Extended activities (Several hours of constant exercise); Fats used as fuel therefore body must slow down (More oxygen required). Fatigue caused by depleted fuel stores, dehydration, increased body temp, physical and mental stress. Anaerobic Exercise Energy supplied by ATP-PC (1- 15 sec) and anaerobic glycolysis (15sec-2min). Energy Stores Athletes should follow strict diets when preparing for events so that fatigue is minimised or delayed. Elite athletes have nutritional programs to aid their performance and recovery.
VCE Physical Education - Unit 3 Metabolic by-products Metabolic by-products are compounds made as a result of chemical reactions within the body. They are the left-overs as such. Eg. When making ATP using phosphocreatine, the by-product is creatine: ADP + PC ATP + creatine By-products can prove harmful to the body by causing it to function in a less efficient way, such as through the effect of hydrogen ions during physical activity. These by-products effect the functioning of the working muscle eg. Ability to break down glycogen, ability to send signals to the muscle and the changing concentration of minerals in and around the muscle. Summary See fig 6.7 p.136 for ATP production during muscular activity.
VCE Physical Education - Unit 3 Current Investigations The role of intracellular metabolites in controlling membrane excitability and the release of intracellular calcium during fatiguing exercise are now hotly being investigated - P i, Ca 2+, Na + and K +. The hydrogen ion theory as a major fatiguing product is hotly debated at present.
VCE Physical Education - Unit 3 Lactic Acid The Myths Busted Lactic acid has a bad reputation. Many people blame it for fatigue, sore muscles, and cramps. Scientists have discovered that lactic acid plays a critical role in generating energy during exercise. When your body makes lactic acid, it splits into lactate ion (lactate) and hydrogen ion. The lactate ion provides fuels for many tissues, helps use dietary carbohydrates, and serves as fuel for liver production of glucose and glycogen. However, lactic acid does have a dark side. The Hydrogen ion is the acid in lactic acid. It interferes with electrical signals in your muscles and nerves, slows energy reactions, and impairs muscle contractions. The burn you feel in intense exercise is caused by hydrogen ion build-up. Inorganic phosphate (P i ) can also have a similar fatiguing effect on the body. So, when you fatigue, don't blame it on lactic acid. Rather, place the blame where it belongs- on hydrogen ion. Lactic Acid
VCE Physical Education - Unit 3 Lactate Inflection Point (LIP) The relationship between blood lactate levels and anaerobic metabolism is still unclear. The term anaerobic threshold (AT) is therefore no longer used in the field exercise physiology and this area of study due to its conflicting meaning. The preferred term, lactate inflection point (LIP), is the point where blood lactate levels increase, as a direct result of increasing exercise intensity. Exercise intensities beyond the LIP causes fatigue due to a reliance on anaerobic pathways to supply ATP and the build up of the metabolic by-products. LIP can be measured in the laboratory using blood analysis or ventilation measurements. It is a good measure of an athletes speed and power of an athlete over a prolonged period. It can also distinguish between middle and long distance runners during a VO 2 max test.
VCE Physical Education - Unit 3 L.I.P
VCE Physical Education - Unit 3 Complete questions 1-5 page 137 of Nelson Physical Education VCE Units 3 & 4. Checkpoints
6. The Redistribution of Blood Flow Muscular Fatigue Mechanisms
VCE Physical Education - Unit 3 Blood Flow and Body Temperature During exercise; Increased demand for oxygen Increased waste products Increased blood volume to working muscles Increased cardiac output Less blood flow to vital organs and more to the working muscles This can cause an increase in core body temperature. The body therefore needs to monitor its balance between cooling and muscle supply (Thermoregulation) Body Temperature Increase Due to blood being brought to the surface (vasodilation of veins) of the skin (cooling mechanism), less blood is supplied to the working muscles. This lessens the ability to produce ATP and lactic may be produced. See fig 6.2 p.138 and 6.8 p.139