Lactate Threshold Flashcards
What system forms lactate?
The short term glycolytic system
Blood lactate does accumulates at all levels of physical activity…True or False
False
Blood lactate does not accumulate at all levels of physical activity
When does blood lactate formation equals lactate
disappearance and oxygen-consuming reactions adequately meet energy demands
During light and moderate PA (<50% VO2max)
In healthy, untrained people, when does blood lactate begin to accumulate
and rise in an exponential manner?
50-55% VO2max
Why does blood lactate occur?
o Glycolytic metabolism predominates and NADH production exceeds the
cells capacity for shuttling its hydrogens down the respiratory chain due to insufficient oxygen supply or oxygen use at the tissue level
o The imbalance in hydrogen release and subsequent oxidation causes pyruvate to accept the excess hydrogens and become lactic acid
o This is converted to lactate in the body and begins to accumulate
What needs to be resynthesised needs to
continue to meet the
energy demands of the
working muscle
ATP baby!!
Transferring hydrogen ions from NADH to pyruvate to form lactate we then free up NAH+ to be recycled through glycolysis and continue to resynthesize ATP
The point at which lactate starts to increase from baseline is termed the ______ ______ and the point at which it begins to increase and accumulate is the ___________ _______
Lactate Threshold
Lactate Turnpoint
What is the definition of Lactate Threshold?
The highest oxygen consumption or exercise
intensity achieved with less than a 1.0mm
increase in blood lactate concentration above the pre-exercise level
Name 4 factors related to lactate threshold
- Low tissue oxygen
- Reliance on glycolysis
- Activation of fast-twitch muscle fibres
- Reduced lactate removal
What is the definition of Lactate Turnpoint?
An increase in blood lactate of greater than
2mmol/L from the previous exercise
intensity
What is Onset of Blood LactateAccumulation
(OBLA)?
When blood lactate concentration systematically increases to 4.0mM
Signifies initiation of an exponential accumulation of lactate in muscle tissue
What are the Metabolic Factors influencing lactate production?
- Inadequate rate of oxygen delivery due to:
◦ Lowered blood oxygen content;
◦ Lower blood flow to skeletal muscle - Imbalance between rates of glycolysis and mitochondrial respiration;
- Increased NADH relative to NAD+;
4.Increased catecholamine’s:
◦ Higher intensities= increased adrenaline/nor adrenaline;
◦ Increased glycolysis
Trained endurance athletes perform steady-rate aerobic exercise at intensities
between 80-90% of VO2max - why might they be able to do this?
- Athletes specific genetic endowment
- Specific local training adaptations that favour less lactate production
• More rapid removal of lactate via greater turnover and/or conversion at any intensity of
exercise
What are the benefits of being endurance-trained?
- Increased delivery of oxygen
- Increased utilisation of oxygen
- Increased oxidation of lactate
Why are training adaptations beneficial?
- Enhance cellular capacity to generate ATP aerobically through glucose and fatty acid catabolism resulting in a lower requirement of anaerobic glycolysis at a given workload
- Conserves glycogen reserves, which inhibits the processes of muscular fatigue and
extends the duration of intense aerobic effort
Lactate Threshold is a functional index of ______ _________
Muscle fatigue
What is termed as a success in endurance events
Sustain a high % of VO2max without accumulating fatigue is of greater
importance
Why is identifying the Lactate Threshold is very important for endurance athletes?
- Sets the highest work-rate that can be sustained without fatigue or rapid glycogen depletion
- Is useful for setting an upper limit for ‘aerobic’ or ‘steady-state’ training
What is the definition for Ventilatory Threshold?
The point where pulmonary ventilation
increases disproportionally relative to increases in oxygen consumption
The excess ventilation comes from the release of CO2 as a result of the ____________________ (finish the scentence)
buffering of lactic acid that begins to accumulate in glycolysis
What does the anaerobic threshold indicate?
Increased reliance on anaerobic processes
(Attempts to validate a linkage between ventilator changes and glycolytic events at the cellular level have however proved elusive)
