Fatigue and Recovery

Question 1

Define LIP.

Answer 1

The lactate inflection
point (LIP) represents the
highest intensity point where
there is a balance between
lactate production and
removal from the blood.

Question 2

Explain why lactate accumulates beyond the LIP.

Answer 2

• The LIP of an individual represents the maximal intensity at which blood lactate is in steady state.
• At exercise intensities beyond an individual’s LIP, blood lactate concentration increases exponentially.

Question 3

Impact of LIP on fatigue.

Answer 3

• Exercise intensities beyond the LIP are associated with a more rapid onset of fatigue due to increased contribution from anaerobic pathways to provide ATP demand.
• Higher the intensity above LIP = more rapid onset of fatigue due to accumulation of by-products from anaerobic metabolism.

Question 4

Describe the relationship between intensity and lactate production.

Answer 4

• The increase of lactate production in the cell is directly proportional to the increase in exercise intensity.
• Blood lactate concentration remains stable during sub-maximal intensities as lactate can be removes at a similar rate of its production in blood.

Question 5

Physiological changes in the body associated with LIP.

Answer 5

• Surge in adrenaline.
• Recruitment of fast-twitch fibres to maintain the required speed/power output.
• Decline in rate at enzymes are able to oxidise fatty acids and pyruvate in mitochondria (create energy aerobically).

Question 6

LIP in trained vs untrained athletes.

Answer 6

• Increase in LIP is due to increase in number, size, and surface area of the mitochondria:
  o Creates more sites for oxidation of fats + CHOs = athlete can work at higher intensities for longer while still working aerobically.
  o Individuals with greater proportion of slow-twitch fibres compared to fast-twitch have greater ability to oxidise fatty acids in mitochondria = have higher LIP.
• LIP untrained = 55-70% O2 Max.
• LIP trained = 75-90% O2 Max.