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Muscular fatigue mechanisms
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a Splits 3 and 4 would shower slower times than splits 1 and 2 due to depletion of PC ( fuel) and
reliance on anaerobic glycolysis. Another factor in the fatigue is reduced rate of energy liberation
presence of lactic acid inhibiting key enzymes.
b Symptoms of fatigue felt at the end of the race would be a heavy feeling in the legs and an increase in
the rate and depth of breathing.
c The most likely causes of fatigue in this event would be depletion of PC and accumulation of lactic
acid. Also, altered levels of metabolic by-products such as ADP and inorganic phosphate.
d The main fuel relied upon during the hurdles event is glycogen.
e The anaerobic energy system would dominate in this event.
f The athlete would have a lower pH level following this event due to the presence of higher levels of
lactic acid.
2 a All three muscle-fibre types in Figure 6.2 maintain a period of contractile activity and this is followed
by a loss of tension as a result of fatigue. Fast-glycolytic fibres fatigue rapidly. Fast-oxidative fibres
have an intermediate capacity to resist fatigue. Slow-oxidative fibres are fatigue-resistant; they can
maintain contractile activity for long periods with little loss of tension.
b The time at which each fibre type experienced a reduction in tension:
Slow-oxidative fibres: not evident
Fast-oxidative fibres: 3 minutes
Fast-glycolytic fibres: 20 seconds
c Fast-oxidative: For activities of three minutes duration the level of tension remains relatively uniform.
At three minutes duration there is a gradual decline in tension. This pattern of decline continues until
the eight-minute mark, with the tension at this stage being reduced by about 33% from the tension at
commencement of the activity.
Fast-glycolytic: The level of tension drops rapidly from the 20-second to the two-minute mark. From
two to four minutes the rate of reduction in tension is slower but the decline in tension continues. After
four minutes duration there is minimal tension in this fibre type.
3 a Sweating at 1.6 L/hr can lead to decreased performance for Brett Lee as a fast bowler in several ways.
First, loss of water and electrolytes will lead to reduced blood volumes, which in turn reduces the
release of blood borne fuels and oxygen to working muscles. Blood flow to skin will also be reduced.
Collectively this means less fuels and oxygen are available to working muscle and hence Lee’s
performance intensity will decrease. However, if Lee does not sweat, he will start to overheat and this
may cause increased lactate production and more deterioration in performance/muscle contractions.
b Some of the symptoms of dehydration include mild to severe thirst, rapid drop in weight, dry lips and
tongue, a decrease in the amount of urine passed (and urine may appear darker than normal), faster
breathing rate than normal, weakness or light headedness, confusion, nausea and headache.
c Less could assess his fluid requirements by weighing himself before and after sport. One kilogram of
weight lost = one litre of fluid lost; two kilograms of weight lost = two 2 litres of fluid lost, and so on.
If he lost weight during the game he would need to increase the amount he drinks during the game.
d To enable Less to have complete hydration and achieve optimal performance, he should:
 not to wait until he is thirsty before drinking
 drink cool water, as it is absorbed more rapidly than warm water
 use a sports drink if the cricket match will see him exercising for more than one hour
 avoid starting exercise dehydrated
 drink plenty of fluid for several hours prior to participating
 drink at least 500 mL of water half to one hour prior to the match
 drink at least 200 mL of water every 15 minutes during a match
 drink at least 500 mL to 1 litre after a match and continue to drink until fluid losses are replaced.
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a The figure shows that as exercise intensity increases a higher percentage of cardiac output is
distributed to working muscles and a lower percentage of cardiac output is distributed to other organs.
b During exercise, the demand for oxygen and nutrients in the muscle cells increases and there is an
increased need to remove wastes from the site of the muscle. In order to achieve this, a greater volume
of blood is delivered to the working muscles.
c During rest, a low percentage of cardiac output is distributed to muscles and a high percentage of
cardiac output is distributed to other organs, while during exercise a high percentage of cardiac output
is distributed to working muscles and a low percentage of cardiac output is distributed to other organs.
d As exercise continues, cardiac output increases and the distribution of cardiac output to various parts
of the body alters. The redistribution of blood flow involves less blood flowing to the vital organs and
extra blood being diverted to the active muscles and the skin. As we exercise, our bodies warm up.
The competing demands of blood supply for the working muscles as well as for assisting in
thermoregulation place significant demands on the cardiovascular system and contribute to fatigue.
Blood is shunted away from working muscles to the skin to increase the cooling effect. This results in
a decreased blood flow and hence decreased oxygen flow to working muscles, forcing the athlete to
slow down. This decrease in oxygen flow to working muscles may also contribute to the increased
accumulation of lactic acid.
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