1. Sian Welch & WendyIngraham - The Crawl -1997 VCE Physical Education - Unit 3

2. Muscular Fatigue Mechanisms 3. Fatigue is the exercise induced reduction in the powergenerating capacity of a muscle and an inability tocontinue the activity.As fatigue sets in, force in your muscles reduces,muscle responses to brain stimuli reduces and activitylevels decrease.VCE Physical Education - Unit 3 4. When and how fast fatigue kicks in is dependantupon 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 (highintensity/anaerobic= quicker fatigue) Level of fitness VCE Physical Education - Unit 3 5. FatigueCauses, signs & symptomsExample LocalFatigue is experienced in a muscle or group ofBiceps during bicepmuscles localised in part of the body. This tends to curlsoccur if the same muscle group is called uponrepeatedly during training (without sufficientrecovery) or performance. Muscles often experienceQuads ina heaviness, tingling pain or cramp-like feelings.snowboardingGeneral This tends to occur after completing a full trainingAfter completing fullsession or competitive game of football, netball or weights sessionthe like. Performers feel that all their muscles areweakenedand sometimes also experience psychological Playing a full game offatigue as well. football etc.Chronic Performers experience an unhealthy breakdown of Chronic fatiguetheir immune system. This is usually caused bysyndromeovertraining as a result of poor training programdesign, inappropriate recovery strategies and/or Overtrainingexcessive competition demands or schedules.Chronic fatigue is dangerous and is oftenaccompanied by increased susceptibility to illness Reoccurring illness oror infections, persistent muscle soreness andinjuriesreduced motivation levels.VCE Physical Education - Unit 3 6. Muscular Fatigue Mechanisms 7. Fatigue mechanisms have been found to be multifactorial. Factorsthat 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 performerVCE Physical Education - Unit 3 8. Fuel depletionMetabolic by- Neuromuscular Elevated bodyproductseventstemperatureIntramuscular Hydrogen ions Decreased Very high coreATP (H+) in plasmafiring of the temperatures and musclecentral nervous Increased ratesPhosphocreatine Inorganic systemof dehydration(PC)phosphate (Pi) Impaired Redistribution Muscle Adenosine sodium (Na+)of blood to assistglycogendiphosphate and potassium cooling Blood glucose (ADP) (K+) gradients Calcium ions(Ca2+)VCE Physical Education - Unit 3 9. Body Causes of FatigueTemperature Metabolic By-products (LA, H+, Pi, Creatine)Energy pathways Fuel stores (PC and glycogen) Hydration levelsBlood flow & redistribution 10. Lactic acid has a badHowever, lactic acid does havereputation. Many peoplea dark side.blame it for fatigue, sore The Hydrogen ion is the acidmuscles, and cramps. in lactic acid. Scientists have discovered It interferes with electricalthat lactic acid plays a criticalsignals in your muscles androle in generating energynerves, slows energyduring exercise. reactions, and impairs muscle When your body makes lacticcontractions.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) candietary carbohydrates, and also have a similar fatiguingserves as fuel for liver effect on the body.production of glucose and So, when you fatigue, dontglycogen.blame it on lactic acid. Rather, place the blame where it belongs- on hydrogen ion. Lactic Acid VCE Physical Education - Unit 3 11. Lactate inflection point (LIP), is LIP can be measured in thethe point where blood lactate laboratory using blood analysislevels increase, as a direct result or ventilation measurements. Itof increasing exercise intensity. is a good measure of anathletes speed and power of Exercise intensities beyond the an athlete over a prolongedLIP causes fatigue due to a period. It can also distinguishreliance on anaerobic pathwaysbetween middle and longto supply ATP and the build updistance runners during a VO 2of the metabolic by-products. max test. LIP is usually triggered above85% of a persons maximumheart rate. When lactate accumulates andsevere blood acidosis occurs(high levels of hydrogen ionsand acidity), fatigue followsquickly.VCE Physical Education - Unit 3 12. Oxygen deficit occursat the beginning ofexercise whenoxygen demand isgreater than oxygensupply. When the body hasan oxygen deficit,ATP is sourced fromthe anaerobicsystems. See graph page 152VCE Physical Education - Unit 3 13. Oxygen Debt (EPOC) Excess Post-exercise Oxygen ConsumptionOxygen 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/EPOCLow intensity activities = a small oxygen deficit, long steady state,small oxygen debt/EPOC VCE Physical Education - Unit 3 14. Most commonly exhausted energy stores are PC andglycogen. Stores of glycogen in the muscle and liver can fuelcontinuous exercise for over 90 mins. Muscle glycogen is generally the first fuel sourceused during aerobic exercise; then liver glycogenand eventually blood-borne and stored fat. Fat conversion to energy is far less efficient thanthat for glycogen, resulting in a reduced intensity. As energy stores are continually depleted, fatigueoccurs and therefore the quality of performancedecreasesVCE Physical Education - Unit 3 15. Predominant Likely causes of fatigueTypes of recoveryenergy systemATP/PCFuel Depletion: Rest recoveryATP & PCLactic Acid Accumulation of metabolic by-products:Non-dietary H+ (hydrogen ions) Active Recovery Pi (inorganic phosphates)MassageNB Lactic Acid is no longer thought toHydro/water based therapies contribute to fatigue. In fact, it is beinge.g. contrasting via hot/cold baths regarded more as a positive performance enhancer rather than a negativeAerobic Fuel Depletion: DietaryGlycogen stores, then fatsHigh GI foodsElevated body temperature leading to: Rehydration via sports drinks:Dehydration Hypertonic to replace glycogenBlood flow away from musclesHypotonic to replace lost fluidsNon-dietaryActive RecoveryMassageHydro/water based therapies VCE Physical Education - Unit 3 16. Muscular Fatigue Mechanisms 17. Metabolic by-products are compounds made as a result ofchemical reactions within the body. They are the left-oversas such.Eg. When making ATP using phosphocreatine, the by-product iscreatine:ADP + PC ATP + creatineBy-products can prove harmful to the body by causing it tofunction in a less efficient way, such as through the effect ofhydrogen ions during physical activity.These by-products effect the functioning of the working muscle eg. Ability to break down glycogen, ability to send signals tothe muscle and the changing concentration of minerals in andaround the muscle. VCE Physical Education - Unit 3 18. Muscular Fatigue Mechanisms 19. Aerobic ExerciseEnergy Stores Less than 20 minutes;Athletes should follow strict dietsNo major fatigue and carbos when preparing for events so and fats used as energy (Verythat fatigue is minimised or little lactic acid). delayed.Extended activities (Several hours of Elite athletes have nutritional constant exercise);programs to aid theirFats used as fuel thereforeperformance and recovery. body must slow down (More oxygen required).Fatigue caused by depleted fuel stores, dehydration, increased body temp, physical and mental stress.Anaerobic ExerciseEnergy supplied by ATP-PC (1- 15 sec) and anaerobic glycolysis (15sec-2min).VCE Physical Education - Unit 3 20. Recovery is used to return the body to pre-exercise conditions and therefore reverse theeffects of fatigue. Efficient recovery enhances adaptations toexercise loads and prepares the performer forfuture training/competition Inefficient recovery delays the removal offatiguing factors and can lead to injuries andover training. Exercisers need to ensure they match theirrecovery to the causes of fatigueVCE Physical Education - Unit 3 21. VCE Physical Education - Unit 3 22. VCE Physical Education - Unit 3 23. Complete reviewquestions on page171-172VCE Physical Education - Unit 3