4. Lactate Threshold / Indices of Exercise Intensity

Question 1

what is pyruvate converted directly into in glycolysis

Answer 1

lactate (reversible)

Question 2

More lactate production in aerobic or anaerobic

Answer 2

anaerobic conditions

Question 3

Gluconeogenesis:

Answer 3

Formation of new glucose
* Cori cycle
* Reverse of glycolysis

Question 4

where does Gluconeogenesis:

Answer 4

liver

Question 5

Lactate Utilisation - Oxidation function

Answer 5

Used as a fuel by neighbouring muscle fibres and other tissues – ‘Lactate Shuttling’
Readily converted to pyruvate
* Enters Krebs cycle

Question 6

Lactate Transport

Answer 6

Transport is via monocarboxylate
transporters (MCTs)

Question 7

Where its MCT1

Answer 7

type I fibres import La-

Question 8

where is MCT4

Answer 8

type II fibres export La-

Question 9

What is the Lactate Threshold

Answer 9

The work rate above which blood lactate concentration consistently exceeds the resting value

Question 10

when does lactate threshold occur

Answer 10

50-60 % VO2 max in healthy individuals
85-90 % VO2 max in endurance trained individuals

Question 11

Does lactate cause fatigue

Answer 11

No
H+ accumulation leads to metabolic
acidosis (linked to fatigue)
* H+ accumulation coincides with lactate accumulation (NOT CAUSED by it)

Question 12

Source of H+

Answer 12

H+ are NOT released through lactate production
H+ released during ATP hydrolysis

Question 13

Aerobic metabolism H+

Answer 13

H+ from ATP hydrolysis enter electron transport chain therefore do not accumulate H+ from ATP hydrolysis

Question 14

Anaerobic metabolism – H+ from ATP hydrolysis are buffered:

Answer 14

H+ + HCO3 < – > H2CO3 <–> H2O + CO2

Question 15

Adaptation to Endurance Training

Answer 15

Increase in:
mitochondrial number and size
oxidative enzymes
MCTs
Other enzymes (e.g. pyruvate
dehydrogenase)
Reliance on fat utilisation
LESS ACCUMULATION OF H+

Question 16

Utility of Lactate Threshold (indicator)

Answer 16

Set training intensity

Monitor training progress
(increased oxidative capacity)

Predict performance– same v02max? higher lactate threshold = better performance

Question 17

Invasive Lactate Threshold Measurement

Answer 17

Lactate test
fingertip blood sample
recorded as last WR before lactate conc -> baseline

Question 18

oxygen uptake reserve (V02R)

Answer 18

maximum oxygen uptake - resting oxygen uptake
Moderate intensity: 40-59 % VO2R
Vigorous intensity: 60-84 % VO2R

Question 19

Heart rate reserve (HRR)

Answer 19

maximum heart rate - resting heart rate
– Moderate intensity: 40-59 % HRR
– Vigorous intensity: 60-84 % HRR

Question 20

Maximum heart rate (HR max)

Answer 20

– Moderate intensity: 64-76 % HR max
– Vigorous intensity: 77-93 % HR max

Question 21

what does Differentiation of Exercise Intensity according to lactate concentration allow

Answer 21

comparability of exercise intensity
between individuals

Question 22

Moderate Intensity Exercise lactate threshold

Answer 22

Below lactate threshold
– No increase in lactate or initial transient increase
– Work not uncomfortable and can be sustained in true steady
state

Question 23

what is critical power

Answer 23

highest work rate that can be sustained without a continued increase in lactate

Question 24

Heavy Intensity Exercise lactate threshold

Answer 24

Above lactate threshold but below critical power
– Increase in arterial lactate but sustained at constant concentration
– Development of metabolic acidosis
– Work rate sustained for limited
duration

Question 25

Very Heavy Intensity Exercise lactate threshold

Answer 25

Above critical power
– Lactate continues to increase throughout exercise to the point of fatigue