SECTION A –
CHAPTER 2
ANSWERS TO QUESTIONS
CHAPTER 2 – FATIGUE AND RECOVERY
Text between pages 18 and 22, answers to questions on page 22 of the text book.
1) a) What is muscle fatigue?2 marks
Answer
• 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.3 marks
Answer
• Depletion of PC stores.
• Lack of O2.
• 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
Answer
• 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 (i.e. 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
Answer
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 VO2max.
• Endurance training based on 80% of VO2max, 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.
.
3) What do you understand by lactate threshold and how the lactate threshold relates to VO2max?
4 marks
Answer
2 marks for definition:
• The lactate threshold is the point at which blood lactate begins to accumulate substantially.
• Above resting concentrations during exercise of increasing intensity.
• Also known as the onset of blood lactate accumulation
(OBLA).
.
2 marks for relationship of lactate threshold to VO2max:
• Lactate threshold represents a significant shift towards anaerobic glycolysis, which is responsible for the formation of lactate or
lactic acid.
.
• Lactate threshold is usually expressed as a percentage
of VO2max at which it occurs.
.
• So ability to perform at a higher percentage of VO2max, reflects a higher lactate threshold.
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APPLIED PHYSIOLOGY TO OPTIMISE PERFORMANCE
4) Describe the possible causes of fatigue during submaximal exercise lasting from 2 to 4 hours.4 marks
Answer
• 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.
5) Explain what you understand by the term ‘buffer’. How does the blood buffer lactic acid?
Answer
1 mark for definition:
• A buffer is a chemical substance that resists abrupt changes in pH.
2 marks for how a buffer works:
• pH is a measure of hydrogen ion (H+) concentration.
• Main source of H+ is carbonic acid, made from carbon dioxide.
• When H+ concentration increases as a result of intense anaerobic exercise.
• H+ reacts with oxyhaemoglobin (buffer) to form haemoglobinic acid.
• These ions are released when H+ concentration falls.
3 marks
6) a) State where and in what conditions lactic acid is commonly found in relatively large amounts.2 marks
Answer
• 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
Answer
2 marks for:
• Lactic acid is converted back to pyruvic acid.
• And the majority of lactate is oxidised within cell mitochondria - i.e. 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 O2 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.
3 marks
Answer
• Converted to glycogen – 20%.
• Converted to protein – 10%.
• Converted to glucose – 5% (lactate shuttle).
d) How does light exercise influence lactate removal?3 marks
Answer
• 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.
Questions and answers 7
SECTION A –
CHAPTER 2
ANSWERS TO QUESTIONS
7) Explain why cool-down is important within an exercise regime.4 marks
Answer
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.
8) Figure 2.9 shows oxygen uptake of an elite games player undertaking exercise followed by a recovery period.
a) Using the appropriate letters, identify the figure 2.9 – oxygen consumption
oxygen deficit and Excess Post Oxygen during exercise and recovery
Consumption (EPOC). 3 marks
b) Why does the elite player incur an oxygen deficit during exercise?
2 marks
Answer
• The oxygen deficit represents the difference between
the oxygen required during the exercise.
• And the oxygen actually consumed during the activity.
VO 2
Answer
• Oxygen deficit = E.
• EPOC = A and D.
E
C
A
D
resting O 2
consumption
B
rest
exercise
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
Answer
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.
3 marks for explanation:
• This component involves the conversion of ADP back to PC and ATP.
• Firstly, there is aerobic conversion of carbohydrates into CO2 and H2O to resynthesise ATP from ADP and Pi.
• 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
Answer
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 (O2).
• Yields 2ATPs per molecule of glucose.
• And carbon dioxide (CO2) .
• 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 (H20) given off.
• Creates 32 or 34 ATPs per molecule of glucose.
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APPLIED PHYSIOLOGY TO OPTIMISE PERFORMANCE
30
50
60
75
90
87
120
93
150
97
180
99
210
101
240
102
% muscle phosphagen restored
9) 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 2.2.
a) Using the results in table 2.2, plot a graph of recovery time against the percentage of muscle phosphagen restored.
3 marks
Answer
Table 2.2 – muscle phosphagen during recovery
• See figure AQ2.1.
recovery time (s) muscle phosphagen restored (%)
figure AQ2.1 – phosphagen recovery
10
10
100%
100
80%
80
60%
60
40%
40
20%
20
00%
00
50
50
100
100
150
150
200
200
250
250
recovery time / s
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
Answer
1 mark for resting value:
• 180-210 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.3 marks
Answer
• Myoglobin is an iron protein molecule located within skeletal muscle.
• Structure is similar to haemoglobin.
• Myoglobin facilitates transportation of O2 from HbO2.
• Into the muscle cell or the mitochondria.
• It acts as a temporary storage site for O2.
10) How could information on oxygen debt recovery be of use to an athlete and coach in designing training sessions?
5 marks
Answer
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 i.e. 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.
3 marks 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.
Questions and answers
9
SECTION A –
CHAPTER 2
ANSWERS TO QUESTIONS
.
.
11) a) Define the term VO2max and describe two main factors which limit VO2max. 3 marks
Answer
1 mark. for definition:
• VO2max represents the greatest rate of oxygen used or consumed by an individual per unit of time.
2 marks for 2 main factors:
• Muscular or cellular tissue system to use oxygen.
• Cardio or vascular or respiratory systems to transport oxygen.
.
b) Describe a field test used to estimate a person’s VO2max.
3 marks
Answer
Many possible tests:
• NCF multistage shuttle run test.
• Subject runs a progressively quicker shuttle run to exhaustion.
• Each step in the progression is numbered.
.
• The step reached by the subject is correlated to a predicted VO2max.
.
.
12) a) Figure 2.10 shows variation in VO2max between three different sports. Suggest reasons for variations in VO2max between these three sports.
3 marks
Answer
Heredity:
.
.
• Variations in VO2max could be related to % fibre type since a higher % of slow twitch fibres.
figure 2.10 – VO2max for
• Will contribute to increased aerobic endurance.
different sports
10
76.9
50
40
30
56.9
55.0
tennis
60
hockey
b) Explain the potential physiological
advantages for endurance .
athletes having a high VO2max. 2 marks
Answer .
• A high VO2max is associated with increased O2 delivery to active muscle.
_
• Or increased O2 extraction by active
muscle tissues (increased a-vO2diff).
.
• Which means that the relative VO2max at a given submaximal workload is
less.
.
• Due to the increased VO2max.
• And the ability to sustain and work at a higher aerobic work rate is
enhanced.
70
distance running
80
VO2max / ml kg-1 min-1
Specificity of training:
• Physiological adaptations in response to training.
• For example, a distance runner will stress the aerobic system in training.
• Whereas the hockey and tennis players will need to stress anaerobic and
aerobic systems.
• Hence the aerobic physiological adaptive response will be less when
compared with the distance runner.
sports