ANSWERS TO QUESTIONS

Transcription

1 SECTION 31 : Fatigue and the recovery process Text between pages 43 to 47, answers to questions on pages 47 to 48 of the text book 1) a) What is muscle fatigue? 2 marks The inability of a muscle to maintain its strength of contraction or tension So that the strength of contraction becomes progressively weaker Until the muscle no longer responds b) Describe the possible causes of fatigue during maximal exercise lasting 2 to 10 seconds Depletion of PC stores Lack of O 2 Neural fatigue or decrease in neural activity 2) During intense exercise, athletes can experience a large increase in lactic acid a) Explain the effect of lactic acid build up on muscle function 4 marks Accumulation of lactic acid in muscle cells causes extreme fatigue and complete loss of muscle function This is because an increase in hydrogen ions (H + - generated from the lactic acid build up) Causes a decrease in ph (called blood acidosis) Which inhibits both anaerobic and aerobic enzymes required for ATP regeneration Thereby inhibiting the contractile processes (ie the ratchet mechanism which brings together the actin and myosin filaments) of the muscle cell Thus leading to muscle fatigue b) Suggest strategies that athletes could use to increase their tolerance to lactic acid 4 marks Bicarbonate loading: By ingesting bicarbonate, prior to a competition, an athlete can increase plasma bicarbonate levels that provide additional buffering capacity Thus allowing higher concentrations of lactate in the blood Theoretically, this could delay the onset of fatigue in all-out anaerobic activity, such as in a 400 metre race Training: Elite endurance athletes may not reach their lactate threshold until 70% to 80% of their VO 2max Endurance training based on 80% of VO 2max, will increase tolerance to lactic acid And so delay the lactic acid threshold even further Anaerobic interval training studies have shown that 30 second bouts of high intensity interval exercise increase the activities of glycolytic enzymes, such as phosphorylase, phosphofructokinase and lactate dehydrogenase from around 10% to 25% This increase in glycolytic capacity will allow the muscle to develop greater tension for a longer period of time As the muscle tissue increases its tolerance to lactate Economy of effort occurs as the athlete becomes more skilful Therefore, there will be decrease in energy demands, thereby delaying the lactate threshold 18

2 SHORT-TERM PREPARATION c) Describe the possible causes of fatigue during submaximal exercise lasting between 2 to 4 hours 4 marks Depletion of muscle and liver glycogen stores Gradual build up of lactic acid Blood acidosis or a fall in muscle ph inhibits enzyme action Build up of H + ions and increases in ADP affect ionic balance of cell membrane wall All this inhibits the contractile processes Neural fatigue, such as failure to stimulate an action potential to cross from the motor neurone to muscle fibre Muscle sheath or fibre damage due to repetitive trauma Fluid loss due to sweating will decrease plasma volume Which reduces blood pressure and peripheral blood blow This means that the heart has to work harder, body temperature rises and fatigue occurs (called the cardiovascular drift) Psychological fatigue, which suggests that fatigue is a perception of the mind 3) What is meant by the Central Governor Theory and how is it related to fatigue? 4 marks This theory outlines a possible psychological element to fatigue It states that fatigue is a perception And an emotional response to situations, such as muscle fatigue The situation is paced by the brain And so the brain decides the time to quit 4) Explain why cool-down is important within an exercise regime 4 marks Cool-down: Continued low level exercise and stretching keeps the capillary beds open within active (muscle) tissue This avoids blood pooling (blood is stored in the venous system as a reservoir until muscle contractions force it back towards the heart) This enables the flushing out of waste products such as lactic acid from the metabolic processes Enabling the body s systems to gradually return to its resting state Which limits muscle soreness (DOMS) And enhances recovery from the exercise period 5) a) State where and in what conditions lactic acid is commonly found in relatively large amounts 2 marks Conditions for lactic acid are anaerobic Lactic acid is found in (muscle cell) sarcoplasm b) There are several ways by which lactic acid can be removed from active muscles Identify the major pathway for the removal of lactic acid and the organs and tissues involved 4 marks 2 marks for: Lactic acid is converted back to pyruvic acid And the majority of lactate is oxidised within cell mitochondria - ie the aerobic energy system pathway 2 marks for two of organs and tissues which are involved in the removal of lactic acid: Oxidation occurs in slow twitch muscle fibres (once sufficient O 2 is available) Blood transports lactic acid (for oxidation) to other organs, which have not been operating under anaerobic conditions Such as liver, kidneys, brain, heart c) Identify the three other ways, with approximate percentages, in which lactic acid is disposed of in the body Converted to glycogen 20% Converted to protein 10% Converted to glucose 5% (lactate shuttle) Chapter 4 19

3 SECTION 31 d) How does light exercise influence lactate removal? Light exercise keeps blood capillaries dilated Avoids blood pooling Flushing oxygenated blood through the muscle Increasing the oxidation of lactic acid and removing lactate from the muscle cells 6) Figure 410 shows oxygen uptake of an elite games player undertaking exercise followed by a recovery period a) Using the appropriate letters, identify the oxygen deficit and Excess Post Oxygen Consumption (EPOC) Oxygen deficit = E EPOC = A and D VO 2 figure 410 oxygen consumption during exercise and recovery E C A b) Why does the elite player incur an oxygen deficit during exercise? 2 marks The oxygen deficit represents the difference between the oxygen required during the exercise And the oxygen actually consumed during the activity resting O 2 consumption rest exercise D B recovery time c) Excess Post Oxygen Consumption (EPOC) is considered to have two components State two aims of the first component and explain how this component is achieved 4 marks 1 mark for one of: The first component is called the alactacid component and involves the restoration of muscle phosphagen So that exercise can begin again within 3 minutes of recovery time for explanation: This component involves the conversion of ADP back to PC and ATP Firstly, there is aerobic conversion of carbohydrates into CO 2 and H 2 O to resynthesise ATP from ADP and P i Then some of the ATP is immediately utilised to create PC using the coupled reaction: ATP + C è ADP + PC d) Describe the process of ATP production that restores the oxygen debt or EPOC 6 marks Description or equivalent diagram: Stage 1 = glycolysis in sarcoplasm Energy yield 2ATPs per molecule of glucose Stage 2 = Kreb s cycle in cell mitochondria In presence of oxygen (O 2 ) Yields 2ATPs per molecule of glucose And carbon dioxide (CO 2 ) Releases H + and e - into next stage Stage 3 = Electron transport stage In inner cristae of mitochondria Oxygen used to create ATP as H + and e - meet With water (H 2 0) given off Creates 32/34 ATPs per molecule of glucose e) Explain why oxygen consumption remains above resting levels after exercise has finished Oxygen is required to replenish PC stores Oxygen is required to resaturate myoglobin Oxygen is required to remove lactic acid Oxygen is required to restore elevated body temperature, breathing rate and heart rate to pre-exercise values 20

4 SHORT-TERM PREPARATION 7) An elite games player performs an interval training session during which the rate of muscle phosphagen levels during the recovery period was recorded The results from this training session are given in Table 42 a) Using the results in Table 42, plot a graph of recovery time against the percentage of muscle phosphagen restored Table 42 muscle phosphagen during recovery recovery time / s muscle phosphagen restored / % See figure Q % b) What resting value would you recommend for a full recovery, and what would be the effect of restarting the exercise after 30 seconds? 2 marks 1 mark for resting value: seconds needed for full recovery 1 mark for the effect of restarting exercise: 50% of muscle phosphagen would have been restored Or 50% muscle phosphagen would have been depleted c) Part of the recovery mechanism after anaerobic exercise involves myoglobin Explain the function of myoglobin during the recovery process Myoglobin is an iron protein molecule located within skeletal muscle Structure is similar to haemoglobin Myoglobin facilitates transportation of O 2 from HbO 2 Into the muscle cell or the mitochondria It acts as a temporary storage site for O 2 8) How could information on oxygen debt recovery be of use to an athlete and coach in designing training sessions? 5 marks 2 marks for two of: Recovery of the phosphagens (PC) is rapid - maximum 2 minutes Therefore athlete is able to perform many repetitions of high quality of short duration ie between 8-10 seconds maximal exercise Build up of lactic acid inhibits enzyme activity and performance deteriorates EPOC removes lactic acid Removal of lactic acid relies on the limited buffering capacity of muscle tissue And much larger buffering capacity of the hydrogencarbonate ion for three of implications for training sessions: Athlete must have adequate rest relief between repetitions Use active recovery between repetitions, and cool-down to facilitate the removal of lactate Variation of workload from one session to the next For example, one high intensity session where the lactic acid system is stressed Followed by a moderately intense aerobic or anaerobic (ATP-PC system) session % muscle phosphagen restored 100% 80% 60% 40% 20% figure Q41 phosphagen recovery recovery time / s Chapter 4 21

5 SECTION ) After a particularly strenuous weight training session, a shot putter may experience muscle soreness immediately after the session and the following day Explain the reasons for this during both these times and identify strategies that could be used to keep the pain to a minimum 8 marks 2 marks for immediately after the session: Muscle or connective tissue damage Acute muscle soreness (at end or immediately after exercise) Accumulation of the end products of exercise namely lactic acid or lactate and creating H + or hydrogen ions Reduced ph level/increased acidity (acting on the pain receptors) Tissue oedema/fluid shifts from blood plasma to damaged tissues (stimulating pain receptors) 2 marks for the following day: Delayed onset muscle soreness (DOMS) (24-48 hours after exercise) Results primarily from eccentric muscle contractions/plyometric work Which places excessive mechanical forces on skeletal muscle tissue Resulting from inflammatory reactions 4 marks for methods of preventing and reducing muscle soreness: Warm-up and the use of active recovery between bouts of work Cool-down keep blood capillaries dilate To flush out lactic acid And to continue adequate supplies of oxygen to working muscles Use of ice baths immediately following the session, will reduce muscle and joint inflammation Use of full body compression clothing during the weight training session, aids venous return and reduces DOMS Have a sports massage, following cool-down to relieve muscle soreness and pain and reduce tissue oedema Gradually increase the training programme by increasing the intensity and repetitions and sessions over a period of weeks Enabling long-term muscle adaptation without severe muscle soreness Use of training principles - moderation, variance and rest in programme planning Exercise different muscle groups on different days to enable muscle groups to recover For example, arm and shoulder strength exercises on day one and leg and trunk strength exercises on day two 10) Recommend a method of optimising glycogen repletion following hard physical activity Active cool-down or Cori cycle or conversion of lactic acid into glycogen High CHO diet as soon as possible after activity to enhance glycogen refuelling Scheduled rest days when little glycogen is used Variations in training loads ie hard, medium to easy so that glycogen stores are not heavily taxed all the time 11) Following an intense training session, explain how the following ergogenic aids assist with the recovery process: having an ice bath, having a massage, wearing full body compression clothing during a cool-down, and ingesting a hypertonic sports drink 8 marks 2 marks for having an ice bath: Will reduce joint and muscle inflammation (hot spots) Produced by torn blood vessels and microtears in muscle tissue 2 marks for having a massage: Stretches soft tissue thereby relieving muscle tension and increasing muscle relaxation Reduce swelling caused by torn blood vessels Increases the movement of interstitial fluids that carry away the waste products of fatigue And stimulate a supply of nutrients, such as O 2 and glucose, which speed up the recovery process Relieves pain and anxiety it is often a pleasant experience Helps prevent injury by dealing with niggles 2 marks for wearing full body compression clothing during a cool-down: Aids venous return Reduces DOMS Hence enhanced recovery 2 marks for ingesting a hypertonic sports drink: Aids rehydration Aids refuelling of depleted glycogen stores Replaces electrolytes (minerals - such as sodium) lost through sweating The inclusion of sodium facilitates water storage