energy transfer - short duration

Question 1

how is lactate formed?

Answer 1

lactic acid breaks down releasing hydrogen ions. The remaining compound combines with sodium or potassium ions to form the salt lactate.

Question 2

why is lactate accumulation a bad thing

Answer 2

as lactate accumulates in the muscles, hydrogen ions are present which acidity. This slows down enzyme activity which affects the breakdown of glycogen causing muscle fatigue.
(the lactate produced in muscles diffuses into the blood and blood lactate can be measured).

Question 3

lactate threshold

Answer 3

as exercise intensity increases there is a crossing of the aerobic/ anaerobic threshold which is also known as lactate threshold and is at the point during exercise at which lactic acid quickly accumulates in the blood

Question 4

what does OBLA stand for?

Answer 4

onset blood lactate accumulation

Question 5

OBLA

Answer 5

as the intensity of exercise increases the body is unable to produce enough oxygen to break down lactate and the levels of lactate accumulation and this is known as OBLA.
- the point when lactate levels go above 4 millimoles per litre

Question 6

why is OBLA useful

Answer 6

measuring OBLA gives an indication of endurance capacity. Some individuals can work at higher levels of intensity than others before OBLA and can delay when the threshold occurs.

Question 7

explain lactate threshold

Answer 7

lactate threshold is expressed as a percentage of V02 max

• training has limited effect on V02 max because it is largely genetically determined.
• When we exercise we tend to work at or just below our lactate threshold (at a level where fatigue is not going to cause our performance to deteriorate)
• the fitter we are, lactate threshold becomes delayed and the higher our lactate threshold as a percentage of our V02 max and here the harder we can work.

Question 8

use multi-stage fitness test to illustrate OBLA

Answer 8

• as test becomes more and more demanding because of reduced time performer reaches a point where energy cannot be provided aerobically therefore it is provided anaerobically.
• levels of lactate increase until muscle fatigue occurs and performer slows down

Question 9

factors affecting the rate of lactate accumulation

Answer 9

1. exercise intensity
2. muscle fibre type
3. rate of blood lactate removal
4. the respiratory exchange ratio
5. fitness of the performer

Question 10

factors affecting the rate of lactate accumulation (exercise intensity)

Answer 10

• increased intensity -> increased demand for energy so OBLA occurs faster
• fast twitch fibres are used for high intensity and can only maintain their workload with glycogen as fuel.
• When glycogen is broken down in absence of oxygen into pyruvic acid lactic acid is formed

Question 11

factors affecting the rate of lactate accumulation (muscle fibre type)

Answer 11

• Slow twitch produce less lactate than fast twitch. This is because as glycogen is broken down in the presence of oxygen much more efficiently and with little lactate production.

Question 12

factors affecting the rate of lactate accumulation (rate of blood lactate removal)

Answer 12

• if the rate of lactate removal is equivalent to rate of lactate production = concentration of blood lactate remains constant
• if lactate production increases lactate accumulates in the blood and OBLA is reached

Question 13

factors affecting the rate of lactate accumulation (the respiratory exchange ratio)

Answer 13

• is ratio of C02 produced compared to 02 consumed
• as this ratio has a value closer to 1:0, glycogen becomes the preferred fuel and there is greater chance of the accumulation of lactate

Question 14

factors affecting the rate of lactate accumulation (fitness of performer)

Answer 14

regular training = better delay of OBLA as adaptations occur to trained muscles
- increased numbers of mitochondria and myoglobin, together with an increase in capillary density improve the capacity for aerobic respiration and therefore avoid the use of the lactate anaerobic system

Question 15

buffering

Answer 15

process which aids the removal of lactate and maintains acidity levels in the blood and muscles.

Question 16

why do elite athletes have greater anaerobic endurance than non-elite

Answer 16

because their body had adapted to cope with higher levels of lactate. Through buffering they will be able to increase the rate of lactate removal and have lower lactate levels

• Buffering soaks up lactate allowing athletes to work at higher intensities for longer before fatigue as well as being able to tolerate higher level of lactate
• there will be a greater number and size of mitochondria and the associated oxidative enzymes, increased capillary density and more myoglobin

Question 17

explain the process of lactate accumulation (6marks)

Answer 17

• if o2 not available during the final stage of glycolysis then energy is produced anaerobically
• LDH converts pyruvate to lactic acid which circulates in blood
• exercise intensity which results in the accumulation of lactic acid in blood is known as lactate threshold
• the increase in exercise intensity will also lead to the onset of blood lactate accumulation (OBLA)
• this is the main limiting factors to exercise duration as athletes will not be able to exercise for extended periods of time once lactic threshold has been reached
• endurance athletes are able to increase their lactate threshold by training which allows them to maintain a higher percentage of their V02 max