KEY KNOWLEDGEKEY SKILLS  Multiple fatigue mechanisms including fuel depletion, metabolic by-products and thermo-regulation and their collective contribution to muscular fatigue under conditions of varied intensity and duration  Recovery strategies, including active and passive types, used to facilitate the body’s return to a pre-exercise state  The take up, transport and utilisation of oxygen during exercise by considering the principles oxygen deficit and steady state, and recovery mechanisms during oxygen debt/EPOC. Explain how the energy systems work together to supply energy during physical activity as well energy system contribution to active and passive recoveries  Understand how using the energy systems under varied exercise intensities and conditions will contribute to fatigue at various levels.  Compare and contrast appropriate recovery methods suited to offset and delay fatigue, facilitate optimal performance and return the body to pre-exercise levels. © Cengage Learning Australia 2011

Fatigue is caused by many factors = multifactorial © Cengage Learning Australia 2011

Lactic acid is continuously being produced and removed – even at rest. When glycogen is broken down pyruvate is formed, and broken down when plenty of oxygen is available. With low oxygen levels / supply, pyruvate becomes lactate and hydrogen ions (H + ). Lactate and hydrogen ions (H + ) enter muscle tissue and are then transported to the blood stream. They are ‘shuttled’ to other muscles and cells where this exists in lower concentrations and the lactate is broken down to produce more energy / ATP or converted into glycogen to again be used as a fuel source. Lactic acid = ‘good guy’ © Cengage Learning Australia 2011

Oxygen deficit – occurs when oxygen supply lags behind oxygen demands – typically at the start of exercise and when exercise intensities rapidly increase – mainly anaerobic energy systems Steady state – occurs when oxygen supply meets oxygen demand – largely aerobic energy system Oxygen debt = EPOC (Excess post-exercise oxygen consumption) – occurs during recovery whilst oxygen levels remain above resting levels – largely aerobic energy system © Cengage Learning Australia 2011

EPOC – It’s sometimes good to extend this via an active recovery © Cengage Learning Australia 2011

ATP is an immediate energy source but very limited (two seconds supply) PC occurs in limited supply at the muscles (10-12 seconds supply) Fuel depletion – ATP and PC These are quick to supply ATP but just as quickly depleted – then muscle glycogen and liver glycogen is used in larger amounts. © Cengage Learning Australia 2011

Muscle glycogen is used first during aerobic activities and then liver glycogen. Once liver glycogen runs low, muscles increasingly use blood-borne fats and then stored fats. The rate of ATP resynthesis decreases quickly (50 – 100 % slower) once the body switches to fats as the main fuel source – this causes slowed performances. Proteins are called upon when fat stores run low which leads to an ever greater slowing down. Fuel depletion – glycogen and fats © Cengage Learning Australia 2011

H + ions – increased amounts cause muscle acidity which slows the actions of glycolytic enzymes and the rate of glycogen breakdown. ( usually associated with LA system dominance ) Inorganic phosphate – reduces the contraction force of muscles and slows the release of calcium ions which also slows neural control of contractions by affecting the sodium potassium balance. ( usually associated with ATP–PC system dominance ) ADP – accumulates during explosive activities and reduces the shortening velocity of contractions and hence decreases the power muscles can exert. ( usually associated with ATP–PC system dominance ) Metabolic by-products © Cengage Learning Australia 2011

Normal core temperature = 36.5 – 37.5 ºC (optimal) 80–90 % of body heat comes from muscles contracting Heat loss from the body occurs mainly by evaporation/sweating This becomes less effective in hot (temps above 36 ºC) and humid environments. Evaporative cooling caused by sweat is assisted by blood being shunted towards the skin’s surface – this takes with it important fuels & oxygen and reduces waste removal rate Decreased plasma volumes resulting from increased sweating cause an increased heart rate to maintain adequate blood supply to working muscles. Elevated body temperature © Cengage Learning Australia 2011

PC is restored as soon as a passive recovery starts. PC comes from amino acids (liver) or dietary creatine (red meats, fish or supplements). PC is rapidly restored during first couple of minutes of EPOC/ oxygen debt. Restoring fuels – PC © Cengage Learning Australia 2011

Glycogen can be ‘restored’ during exercise and athletes often consume hypertonic sports drinks to lessen glycogen being drained from the liver (during moderate exercise one gram of glucose is drained per minute). High GI foods should be consumed within first 30 to 60 mins of recovery to ensure rapid and complete restoration within 24 h. Delayed intake will delay restoration. Restoring fuels – glycogen NB – Carbohydrates not stored at the muscles and liver will be converted to fat © Cengage Learning Australia 2011

H + ions – removed quickest during an active recovery (same activity at reduced intensity) Why? – Oxygen levels remain above resting levels for longer and this assists breakdown. Removal of metabolic by-products A ‘muscle pump’ is created when muscles squeeze blood vessels, more oxygen is supplied to working muscles and wastes are removed faster. Promotes shunting to areas of lower concentration Promotes venous flow and prevents venous pooling Massage and contrast bathing also promote blood flow and speed up H + removal from muscles. © Cengage Learning Australia 2011

The movement of sodium and potassium is crucial to the transmission of messages to and from muscles. Sodium, potassium, calcium and chloride are electrolytes critical to ATP resynthesis. Electrolyte or sports drinks and excellent for quick electrolyte replacement and in counteracting fatigue. Sodium, potassium and other electrolytes © Cengage Learning Australia 2011

ice baths/cool pools when off the field/court or at end of activity – (body temperature can cool down 25 times faster when immersed in cold water) cool/cold showers (when off the field/court or at end of activity) ice vests (during breaks in play, interchange situations) refrigerated cool rooms (during long breaks in play when players are taken from the field) ventilation/fans (on side of playing venue) protective shade (trees, surrounding buildings, shade sails or umbrellas) reduced/modified clothing (to avoid overheating it’s recommended that loose fitting, lightweight and light colored clothing is worn). Counteracting dehydration and elevated body temperature © Cengage Learning Australia 2011