Energy Transfer During Short Duration

Question 1

What is the lactate threshold?

Answer 1

The point at which lactic acid rapidly accumulates in the blood.

Question 2

What happens when exercise intensity increases?

Answer 2

The body moves from working aerobically to anaerobically.

This crossing of the threshold is know as the lactate threshold.

Question 3

Why does lactate rapidly accumulate when exercise intensity increases?

Answer 3

The body can deal with it effectively when small amounts are produced constantly.

As the intensity of exercise increases and the body is unable to produce enough oxygen to break down lactate, the levels of lactate build up/accumulation and this is known as OBLA.

Question 4

What is OBLA?

Answer 4

The point when lactate levels go above 4 millimoles per litre.

Onset Blood Lactate Accumulation

Question 5

How much lactate is in the blood at rest?

Answer 5

Approx 1-2 millimoles per litre of lactate can be found in the blood.

Question 6

How much lactate is in the blood during exercise?

Answer 6

Lactate will rise dramatically and as it starts to accumulate, OBLA occurs - this is usually around 4 millimoles per litre.

Question 7

What can OBLA tell you?

Answer 7

It gives an indication of endurance capacity

Question 8

What can lactate threshold be expressed as?

Answer 8

A % of VO2 max.

Question 9

What is VO2 max?

Answer 9

The maximum amount of oxygen that can be utilised by the muscles per minute.

Question 10

How are lactate threshold and VO2 max related?

Answer 10

Lactate threshold is expressed as a % of VO2 max

Average performers may have a LT that is 50-60% of their VO2 max, whereas elite performers may have a LT that is 70-80-90% of their VO2 max.

Question 11

What are the factors affecting the rate of lactate accumulation?

Answer 11

Exercise intensity 
Muscle fibre type
Rate of blood lactate removal 
The respiratory exchange ratio 
Fitness of the performer

Question 12

What is meant by exercise intensity?

Answer 12

The higher the exercise intensity, the greater the demand for energy (ATP) and the faster OBLA occurs because when glycogen is broken down anaerobically into pyruvic acid, lactic acid is formed.

Question 13

What is meant by muscle fibre type?

Answer 13

Slow twitch fibre produce less lactate than fast twitch fibres.

When slow twitch fibres use glycogen as a fuel, due to the presence of oxygen, the glycogen can be broken down much more effectively and with little lactate production.

Question 14

What is meant by rate of blood lactate removal?

Answer 14

If the rate of lactate removal is lower than the rate of lactate production, lactate will start to accumulate in the blood until OBLA is reached.

Question 15

What is meant by the respiratory exchange ratio?

Answer 15

This is described in more detail later on in this chapter, but when the ratio has a value close to 1.0 glycogen becomes the preferred fuel and there is a greater chance of the accumulation of lactate.

Question 16

What is meant by the fitness of the performer?

Answer 16

A person who trains regularly will be in a better position to delay OBLA, as adaptions 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 anaerobic glycolytic system.

Question 17

Why do elite sprinters and power athletes have better anaerobic endurance?

Answer 17

Their body has adapted to cope with higher levels of lactate.

In addition through a process called buffering, they will be able to increase the rate of lactate removal and consequently have lower lactate levels.

This means the athletes will be able to work higher intensities for longer before fatigue sets in.

Question 18

What is buffering?

Answer 18

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