Muscular fatigue mechanisms 2011
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Muscular fatigue mechanisms 2011 Muscular fatigue mechanisms 2011 Presentation Transcript

  •  Sian Welch & Wendy Ingraham - The Crawl - 1997 VCE Physical Education - Unit 3
  • Muscular Fatigue Mechanisms
  • Fatigue is the exercise induced reduction in the power generating capacity of a muscle and an inability to continue the activity.As fatigue sets in, force in your muscles reduces, muscle responses to brain stimuli reduces and activity levels decrease. VCE Physical Education - Unit 3
  •  When and how fast fatigue kicks in is dependant upon the following: ◦ Type of activity (intermittent/continuous) ◦ Muscle fibre type used (slow/fast twitch. Slow=longer) ◦ Type of muscle contraction (isotonic/isometric- fastest/isokinetic) ◦ Intensity and duration of activity (high intensity/anaerobic= quicker fatigue) ◦ Level of fitness VCE Physical Education - Unit 3
  • Fatigue Causes, signs & symptoms Example Local Fatigue is experienced in a muscle or group of Biceps during bicep muscles localised in part of the body. This tends to curls occur if the same muscle group is called upon repeatedly during training (without sufficient recovery) or performance. Muscles often experience Quads in a heaviness, tingling pain or cramp-like feelings. snowboardingGeneral This tends to occur after completing a full training After completing full session or competitive game of football, netball or weights session the like. Performers feel that all their muscles are ‘weakened’ and sometimes also experience psychological Playing a full game of fatigue as well. football etc.Chronic Performers experience an unhealthy breakdown of Chronic fatigue their immune system. This is usually caused by syndrome overtraining as a result of poor training program design, inappropriate recovery strategies and/or Overtraining excessive competition demands or schedules. Chronic fatigue is dangerous and is often accompanied by increased susceptibility to illness Reoccurring illness or or infections, persistent muscle soreness and injuries reduced motivation levels. VCE Physical Education - Unit 3
  • Muscular Fatigue Mechanisms
  • Fatigue mechanisms have been found to be multifactorial. Factors that help determine when performance will deteriorate include:1. Exercise type, duration and intensity2. Types of muscular contractions3. Physical fitness or conditioning4. Age5. Diet6. Environmental factors7. Mental state of the performer VCE Physical Education - Unit 3
  • Fuel depletion Metabolic by- Neuromuscular Elevated body products events temperature•Intramuscular • Hydrogen ions • Decreased • Very high coreATP (H+) in plasma ‘firing’ of the temperatures• and muscle central nervous • Increased ratesPhosphocreatine • Inorganic system of dehydration(PC) phosphate (Pi) • Impaired • Redistribution• Muscle • Adenosine sodium (Na+) of blood to assistglycogen diphosphate and potassium cooling• Blood glucose (ADP) (K+) gradients • Calcium ions (Ca2+) VCE Physical Education - Unit 3
  • Body Causes of FatigueTemperature Metabolic By-products (LA, H+, Pi, Creatine) Energy pathways Fuel stores (PC and glycogen) Hydration levels Blood flow & redistribution
  • Lactic acid has a bad However, lactic acid does have reputation. Many people a dark side. blame it for fatigue, sore  The Hydrogen ion is the acid muscles, and cramps. in lactic acid. Scientists have discovered  It interferes with electrical that lactic acid plays a critical signals in your muscles and role in generating energy nerves, slows energy during exercise. reactions, and impairs muscle When your body makes lactic contractions. acid, it splits into lactate ion  The burn you feel in intense (lactate) and hydrogen ion. exercise is caused by The lactate ion provides fuels hydrogen ion build-up. for many tissues, helps use  Inorganic phosphate (Pi) can dietary carbohydrates, and also have a similar fatiguing serves as fuel for liver effect on the body. production of glucose and  So, when you fatigue, dont glycogen. 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), is  LIP can be measured in the the point where blood lactate laboratory using blood analysis levels increase, as a direct result or ventilation measurements. It of increasing exercise intensity. is a good measure of an athletes speed and power of Exercise intensities beyond the an athlete over a prolonged LIP causes fatigue due to a period. It can also distinguish reliance on anaerobic pathways between middle and long to supply ATP and the build up distance runners during a VO 2 of the metabolic by-products. max test. LIP is usually triggered above 85% of a persons maximum heart rate. When lactate accumulates and severe blood acidosis occurs (high levels of hydrogen ions and acidity), fatigue follows quickly. VCE Physical Education - Unit 3
  •  Oxygen deficit occurs at the beginning of exercise when oxygen demand is greater than oxygen supply. When the body has an oxygen deficit, ATP is sourced from the anaerobic systems. See graph page 152 VCE Physical Education - Unit 3
  • Oxygen Debt (EPOC) Excess Post- exercise Oxygen Consumption•Oxygen debt is defined as the volume of oxygen used duringrecovery from exercise in excess of resting oxygen consumption.•Occurs after anaerobic exercise.•Divided into 2 parts. 1(fast)- restores PC in approximately 2-3minutes. 2-3 litres of oxygen is consumed to provide thisresynthesisation. 2 (slow)-removes lactic acid through buffering.Recovery depends on usage and metabolic disturbances duringactivity.•High intensity activities = a large oxygen deficit, small (or no)steady state, large oxygen deficit/EPOC•Low intensity activities = a small oxygen deficit, long steady state,small oxygen debt/EPOC VCE Physical Education - Unit 3
  •  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
  • Predominant Likely causes of fatigue Types of recoveryenergy systemATP/PC Fuel Depletion: Rest recovery ATP & PCLactic Acid Accumulation of metabolic by-products: Non-dietary H+ (hydrogen ions) Active Recovery Pi (inorganic phosphates) Massage NB – Lactic Acid is no longer thought to Hydro/water based therapies contribute to fatigue. In fact, it is being e.g. contrasting via hot/cold baths regarded more as a positive performance enhancer rather than a negativeAerobic Fuel Depletion: Dietary Glycogen stores, then fats High GI foods Elevated body temperature leading to: Rehydration via sports drinks: Dehydration Hypertonic to replace glycogen Blood flow away from muscles Hypotonic to replace lost fluids Non-dietary Active Recovery Massage Hydro/water based therapies VCE Physical Education - Unit 3
  • Muscular Fatigue Mechanisms
  • 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 + creatineBy-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. VCE Physical Education - Unit 3
  • Muscular Fatigue Mechanisms
  • Aerobic Exercise Energy Stores Less than 20 minutes; Athletes should follow strict diets No major fatigue and carbo’s when preparing for events so and fats used as energy (Very that fatigue is minimised or little lactic acid). delayed.Extended activities (Several hours of  Elite athletes have nutritional constant exercise); programs to aid their Fats used as fuel therefore performance and recovery. 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). VCE Physical Education - Unit 3
  •  Recovery is used to return the body to pre- exercise conditions and therefore reverse the effects of fatigue. Efficient recovery enhances adaptations to exercise loads and prepares the performer for future training/competition Inefficient recovery delays the removal of fatiguing factors and can lead to injuries and over training. Exercisers need to ensure they match their recovery to the causes of fatigue VCE Physical Education - Unit 3
  • VCE Physical Education - Unit 3
  • VCE Physical Education - Unit 3
  • Complete reviewquestions on page 171-172 VCE Physical Education - Unit 3